Abstract: BACKGROUND: Ethiopia plans to increase its electricity power supply by five-fold over the next five years to fulfill the needs of its people and support the economic growth based on large hydropower dams. Building large dams for hydropower generation may increase the transmission of malaria since they transform ecosystems and create new vector breeding habitats. The aim of this study was to assess the effects of Gilgel-Gibe hydroelectric dam in Ethiopia on malaria transmission and changing levels of prevalence in children. METHODS: A cross-sectional, community-based study was carried out between October and December 2005 in Jimma Zone, south-western Ethiopia, among children under 10 years of age living in three 'at-risk' villages (within 3 km from dam) and three 'control' villages (5 to 8 km from dam). The man-made Gilgel-Gibe dam is operating since 2004. Households with children less than 10 years of age were selected and children from the selected households were sampled from all the six villages. This included 1,081 children from 'at-risk' villages and 774 children from 'control' villages. Blood samples collected from children using finger prick were examined microscopically to determine malaria prevalence, density of parasitaemia and identify malarial parasite species. RESULTS: Overall 1,855 children (905 girls and 950 boys) were surveyed. A total of 194 (10.5%) children were positive for malaria, of which, 117 (60.3%) for Plasmodium vivax, 76 (39.2%) for Plasmodium falciparum and one (0.5%) for both P. vivax and P. falciparum. A multivariate design-based analysis indicated that, while controlling for age, sex and time of data collection, children who resided in 'at-risk' villages close to the dam were more likely to have P. vivax infection than children who resided farther away (odds ratio (OR) = 1.63, 95% CI = 1.15, 2.32) and showed a higher OR to have P. falciparum infection than children who resided in 'control' villages, but this was not significant (OR = 2.40, 95% CI = 0.84, 6.88). A classification tree revealed insights in the importance of the dam as a risk factor for malaria. Assuming that the relationship between the dam and malaria is causal, 43% of the malaria occurring in children was due to living in close proximity to the dam. CONCLUSION: This study indicates that children living in close proximity to a man-made reservoir in Ethiopia are at higher risk of malaria compared to those living farther away. It is recommended that sound prevention and control programme be designed and implemented around the reservoir to reduce the prevalence of malaria. In this respect, in localities near large dams, health impact assessment through periodic survey of potential vectors and periodic medical screening is warranted. Moreover, strategies to mitigate predicted negative health outcomes should be integral parts in the preparation, construction and operational phases of future water resource development and management projects.

Abstract: Monitoring Leishmania infection in sand flies is important for understanding the eco-epidemiology of kala-azar and assessing the impact of the recently launched kala-azar control programme in the Indian subcontinent. We applied a PCR technique that targets rRNA genes to estimate the natural incidence of Leishmania infection in sand flies sampled in six villages of the Terai region of Nepal. Amplifications were made on 135 pools of sand flies and confirmed by sequencing. Seven pools were found to be PCR positive: in five of them we identified the rDNA signature found in Leishmania spp., whereas two other pools revealed a sequence compatible with other trypanosomatids. Different methodologies were applied to evaluate the infection rate from pools of unequal size and estimated the infection rate to range from 0.468% to 0.578% for the Leishmania group and from 0.185% to 0.279% for the non-Leishmania group. Our results highlight the diversity of flagellate infections likely to be encountered in Phlebotomus argentipes populations. Our methodology allows clear discrimination of Leishmania from other trypanosomatids and should be applied on larger insect samples or in longitudinal studies.

Abstract: Objective. In India, Scheduled Castes and Scheduled Tribes (ST/SC) have been excluded from Hindu society for thousands of years. Together, they comprise over 24% of India's population and still suffer worse health conditions compared to the rest of the Indian population. This paper decomposes the gap in child malnutrition between the ST/SC and the remaining Indian population, looking at both the ST/SC's disadvantageous distribution of health determinants and possible discriminatory or behavioral differences. Design and setting. A Blinder-Oaxaca decomposition was applied to decompose the gap in children's average height-for-age z scores, using data from the 1998/1999 Indian Demographic Health Survey. Results. The gap was found to be primarily caused by the ST/SC's lower wealth, education and use of health care services, but also differences in the effects of health determinants played an important role. It was found that within rural areas ST/SC are not necessarily located further from educational and health care facilities. Conclusions. The use of Oaxaca type decomposition can be very useful when studying ethnic inequalities in health as it explicitly allows for discriminatory or behavioral effects. The results did not point to discrimination against ST/SC regarding health care or education. However, in the quest to increase health care use and education among ST/SC, policy makers will have to take into account all the barriers to these services, including those related to cultural sensitivity and acceptability.

Abstract: BACKGROUND: Taenia solium cysticercosis is an important zoonosis in many developing countries. Human neurocysticercosis is recognised as an important cause of epilepsy in regions where the parasite occurs. However, it is largely underreported and there is a lack of data about the disease burden. Because a body of information on human and porcine cysticercosis in Cameroon is becoming available, the present study was undertaken to calculate the impact of this neglected zoonosis. METHODS: Both the cost and Disability Adjusted Life Year (DALY) estimations were applied. All necessary parameters were collected and imported in R software. Different distributions were used according to the type of information available for each of the parameters. FINDINGS: Based on a prevalence of epilepsy of 3.6%, the number of people with neurocysticercosis-associated epilepsy was estimated at 50,326 (95% CR 37,299-65,924), representing 1.0% of the local population, whereas the number of pigs diagnosed with cysticercosis was estimated at 15,961 (95% CR 12,320-20,044), which corresponds to 5.6% of the local pig population. The total annual costs due to T. solium cysticercosis in West Cameroon were estimated at 10,255,202 Euro (95% CR 6,889,048-14,754,044), of which 4.7% were due to losses in pig husbandry and 95.3% to direct and indirect losses caused by human cysticercosis. The monetary burden per case of cysticercosis amounts to 194 Euro (95% CR 147-253). The average number of DALYs lost was 9.0 per thousand persons per year (95% CR 2.8-20.4). INTERPRETATION: This study provides an estimation of the costs due to T. solium cysticercosis using country-specific parameters and including the human as well as the animal burden of the zoonotic disease. A comparison with a study in South Africa indicates that the cost of inactivity, influenced by salaries, plays a predominant role in the monetary burden of T. solium cysticercosis. Therefore, knowing the salary levels and the prevalence of the disease might allow a rapid indication of the total cost of T. solium cysticercosis in a country. Ascertaining this finding with additional studies in cysticercosis-endemic countries could eventually allow the estimation of the global disease burden of cysticercosis. The estimated number of DALYs lost due to the disease was higher than estimates already available for some other neglected tropical diseases. The total estimated cost and number of DALYs lost probably underestimate the real values because the estimations have been based on epilepsy as the only symptom of cysticercosis.

Abstract: BACKGROUND: Despite a successful control programme, malaria has not completely disappeared in Vietnam; it remains endemic in remote areas of central Vietnam, where standard control activities seem to be less effective. The evolution of malaria prevalence and incidence over two and half years in a rural area of central Vietnam, after the introduction of community-based monitoring of malaria cases, is presented. METHODS: After a complete census, six cross-sectional surveys and passive detection of malaria cases (by village and commune health workers using rapid diagnostic tests) were carried out between March 2004 and December 2006 in Ninh-Thuan province, in a population of about 10,000 individuals. The prevalence of malaria infection and the incidence of clinical cases were estimated. RESULTS: Malaria prevalence significantly decreased from 13.6% (281/2,068) in December 2004 to 4.0% (80/2,019) in December 2006. Plasmodium falciparum and Plasmodium vivax were the most common infections with few Plasmodium malariae mono-infections and some mixed infections. During the study period, malaria incidence decreased by more than 50%, from 25.7/1,000 population at risk in the second half of 2004 to 12.3/1,000 in the second half of 2006. The incidence showed seasonal variations, with a yearly peak between June and December, except in 2006 when the peak observed in the previous years did not occur. CONCLUSION: Over a 2.5-year follow-up period, malaria prevalence and incidence decreased by more than 70% and 50%, respectively. Possibly, this could be attributed to the setting up of a passive case detection system based on village health workers, indicating that a major impact on the malaria burden can be obtained whenever prompt diagnosis and adequate treatment are available.

Abstract: OBJECTIVE: To compare a PCR assay and direct agglutination test (DAT) for the detection of potential markers of Leishmania infection in 231 healthy subjects living in a kala-azar endemic focus of Nepal. METHODS: The sample was composed of 184 (80%) persons without any known history of KA and not living in the same house as known kala-azar cases (HNK), 24 (10%) Healthy Household Contacts (HHC) and 23 (10%) past kala-azar cases which had been successfully treated (HPK). RESULTS: PCR and DAT positivity scores were, respectively: HNK, 17.6% and 5.6%; HHC, 12.5% and 20.8%; HPK, 26.1% and 95.7%. The ratio PCR-positives/DAT-positives was significantly higher in HNK (ratio = 3.1) than in HHC (ratio = 0.6, P = 0.036) and in HPK (ratio = 0.2, P = 0.012). The ratio PCR-positives/DAT-positives did not significantly differ between HHC (ratio = 0.6) and HPK (ratio = 0.2, P = 0.473). The positive agreement index between PCR and DAT in HNK was 5%; in HHC, 0%; in HPK, 43%. CONCLUSIONS: Our study highlights the specific character of PCR and DAT for the exploration of Leishmania asymptomatic infections. PCR is probably more informative for very recent infections among HNK, while DAT provides more information among HHC and HPK, a feature likely related to the power of serology to track less recent infections.

Abstract: OBJECTIVE: To determine whether the use of long-lasting insecticidal nets (LLINS) at household level are effective in reducing the abundance of Phlebotomus argentipes, vector of anthroponotic visceral leishmaniasis in India, Nepal and Bangladesh. METHODS: The impact of two long-lasting nets (Olyset and PermaNet) on indoor sandfly abundance was evaluated in selected houses of three endemic hamlets in Bihar (India). It was assumed that most sandflies breed inside the houses and that LLINs would progressively reduce the indoor density during the reproduction season. A campaign of indoor spraying with dichloro-diphenyl-trichloroethane (DDT) interfered with the trial but did not affect the sandfly population. Results Only the density of males of P. argentipes was significantly reduced by both the LLINs but not the females. CONCLUSIONS: These findings suggest that most female sandflies are coming from outside and that LLINs do not reduce their entry rate.

Abstract: BACKGROUND: In Central Vietnam, forest malaria remains difficult to control due to the complex interactions between human, vector and environmental factors. METHODS: Prior to a community-based intervention to assess the efficacy of long-lasting insecticidal hammocks, a complete census (18,646 individuals) and a baseline cross-sectional survey for determining malaria prevalence and related risk factors were carried out. Multivariate analysis using survey logistic regression was combined to a classification tree model (CART) to better define the relative importance and inter-relations between the different risk factors. RESULTS: The study population was mostly from the Ra-glai ethnic group (88%), with both low education and socio-economic status and engaged mainly in forest activities (58%). The multivariate analysis confirmed forest activity, bed net use, ethnicity, age and education as risk factors for malaria infections, but could not handle multiple interactions. The CART analysis showed that the most important risk factor for malaria was the wealth category, the wealthiest group being much less infected (8.9%) than the lower and medium wealth category (16.6%). In the former, forest activity and bed net use were the most determinant risk factors for malaria, while in the lower and medium wealth category, insecticide treated nets were most important, although the latter were less protective among Ra-glai people. CONCLUSION: The combination of CART and multivariate analysis constitute a novel analytical approach, providing an accurate and dynamic picture of the main risk factors for malaria infection. Results show that the control of forest malaria remains an extremely complex task that has to address poverty-related risk factors such as education, ethnicity and housing conditions.

Abstract: Theileria parva is the causative agent of East Coast fever (ECF), an important cattle disease in East and Central Africa. One of the methods for control of ECF is 'infection and treatment', a procedure in which an animal is infected with the live parasite and at the same time treated with a long-acting oxytetracycline formulation, restraining the infection and allowing a protective cellular immune response to develop. Optimal immunizing doses were estimated using models of trichotomous response: dysimmunization (death or severe reaction during immunization), immunization failure (death or severe reaction during lethal challenge) and successful immunization (neither dysimmunization nor immunization failure). In this paper we present methods of interpreting immunization trials and apply these methods to previously unpublished data from two such trials: one with a mixture of three T. parva stocks and one with a single T. parva stock. We explain why titration trials conducted with a cocktail of antigens could predict a suboptimal immunization dose. Indeed it is possible for a combination of three individually efficient stocks to result in a mixture with which optimal immunization response might be difficult to achieve, because of averaging effects. The corresponding interpretation provides insights into why standard immunization trials for T. parva have not yielded the results that might be expected of them. The results of this work may also have implications for the use of antigen cocktails in cancer, HIV and malaria vaccine trials.

Abstract: OBJECTIVE: The objectives of this study were to report on socioeconomic inequality in childhood malnutrition in the developing world, to provide evidence for an association between socioeconomic inequality and the average level of malnutrition, and to draw attention to different patterns of socioeconomic inequality in malnutrition. METHODS: Both stunting and wasting were measured using new WHO child growth standards. Socioeconomic status was estimated by principal component analysis using a set of household assets and living conditions. Socioeconomic inequality was measured using an alternative concentration index that avoids problems with dependence on the mean level of malnutrition. FINDINGS: In almost all countries investigated, stunting and wasting disproportionately affected the poor. However, socioeconomic inequality in wasting was limited and was not significant in about one third of countries. After correcting for the concentration index's dependence on mean malnutrition, there was no clear association between average stunting and socioeconomic inequality. The latter showed different patterns, which were termed mass deprivation, queuing and exclusion. Although average levels of malnutrition were higher with the new WHO reference standards, estimates of socioeconomic inequality were largely unaffected by changing the growth standards. CONCLUSION: Socioeconomic inequality in childhood malnutrition existed throughout the developing world, and was not related to the average malnutrition rate. Failure to tackle this inequality is a cause of social injustice. Moreover, reducing the overall rate of malnutrition does not necessarily lead to a reduction in inequality. Policies should, therefore, take into account the distribution of childhood malnutrition across all socioeconomic groups.

Abstract: The efficacy of light traps for collecting sandflies (Diptera: Psychodidae) varies both inter-specifically and intra-specifically (by gender and physiological status) as a result of significant differences in phototropic and other behavioural characteristics. The efficacy of miniature CDC light traps for collecting Phlebotomus argentipes Annandale & Brunetti, a vector of Leishmania donovani Laveran & Mesnil (Kinetoplastida: Trypanosomatidae), was assessed in the Indian state of Bihar. Sandflies were collected during the night from 16 houses in each of three villages over 3 months (four times at fortnightly intervals) using CDC light traps indoors, and by aspirator collection (carried out by one person for 30 min/house) from the walls of the same houses the following morning. Incidence rate ratios (IRRs) between CDC light trap collections and aspirator collections were obtained through a negative binomial regression with household as random effect. CDC light traps were especially effective in catching males (IRR 3.08, 95% confidence interval [CI] 2.12-4.46) and unfed females (IRR 3.50, 95% CI 2.37-5.16) of P. argentipes, and to a lesser extent gravids (IRR 1.77, 95% CI 1.07-2.93). However, only a relatively small proportion of all blood-fed P. argentipes were collected by light trap (IRR 0.45, 95% CI 0.28-0.73). Despite its limitations in collecting blood-fed female sandflies, the CDC light trap appears to trap a sufficient proportion of the indoor population of sandflies for sampling purposes, and as this light trap is also more convenient and more easily standardized than the aspirator method, we conclude that it is the most efficient method for monitoring P. argentipes populations in the Indian subcontinent.

Abstract: Interpretation of the result of a diagnostic test depends not only on the actual test result(s) but also on information external to this result, namely the test's sensitivity and specificity. This external information (also called prior information) must be combined with the data to yield the so-called updated, posterior estimates of the true prevalence and the test characteristics. The Bayesian approach offers a natural, intuitive framework in which to carry out this estimation process. The influence of the prior information on the final result may not be ignored. Guidance for the choice of prior information not in conflict with the data can be obtained from a set of statistics and indices (DIC, p(D), Bayes-p).

Abstract: BACKGROUND: To assess the inequity in seeking needed outpatient services in Iran and to investigate its influential factors. METHOD: The data were taken from a nation-wide Iranian health survey conducted in 2003. This study is based on individuals aged 15 years and over who had mentioned their need to seek outpatient care within two weeks prior to the day of the interview. The outcome was seeking needed outpatient care. The independent variables included respondents' age, gender, marital status, education, occupation, index of household economic status, health insurance status and residential place (urban vs. rural).RESULTS: Sixty-nine point five percent of those in need sought outpatient care. The rich (OR: 2.38, 95% CI: 1.64 - 3.43) and the health insured (OR: 1.62, 95% CI: 1.25 - 2.08), the pensioners and the retired (OR: 2.26, 95% CI: 1.22 - 4.20), the housewives (OR: 1.77, 95% CI: 1.07 - 2.95) were more likely to seek outpatient care than other occupations. On the other hand, people living in remote rural areas (OR: 0.40, 95% CI: 0.28 - 0.57) were less likely to seek their needed outpatient care than those living in main rural areas and urban areas. CONCLUSIONS: As in different parts of the world, differences in seeking needed healthcare still exist across different groups in Iran. Indeed, seeking outpatient care in Iran is related not only to health system functions--like health insurance and health facilities--but also on factors beyond the scope of health authorities such as economic status and occupation. This study can be instrumental for the recent five-year Economic, Social and Cultural Development Plan of Iran which identified the reduction of inequalities in social determinants of health [corrected]

Abstract: A comparison of mean corpuscular volume (MCV) and packed cell volume (PCV) was made between cattle undergoing lethal and non-lethal reactions following experimental infections with the apicomplexan protozoa, Theileria parva Katete. This work confirmed that anaemia occurs in infected animals. However, the fall in PCV was steeper in lethal reactions compared to non-lethal reactions. Our results show that animals with initially lower MCV values are more prone to fatal reaction, despite having normal PCV profiles. The study also found that small red blood cells are more likely to be infected with T. parva. These findings suggest that animals with a higher proportion of small red blood cells in circulation will be more likely to succumb to T. parva infections. The potential for using MCV as a predictor of the outcome of infection challenge is discussed.

Abstract: ABSTRACT: BACKGROUND: Malnutrition is a major public health and development concern in the developing world and in poor communities within these regions. Understanding the nature and determinants of socioeconomic inequality in malnutrition is essential in contemplating the health of populations in developing countries and in targeting resources appropriately to raise the health of the poor and most vulnerable groups. METHODS: This paper uses a concentration index to summarize inequality in children's height-for-age z-scores in Ghana across the entire socioeconomic distribution and decomposes this inequality into different contributing factors. Data is used from the Ghana 2003 Demographic and Health Survey. RESULTS: The results show that malnutrition is related to poverty, maternal education, health care and family planning and regional characteristics. Socioeconomic inequality in malnutrition is mainly associated with poverty, health care use and regional disparities. Although average malnutrition is higher using the new growth standards recently released by the World Health Organization, socioeconomic inequality and the associated factors are robust to the change of reference population. CONCLUSION: Child malnutrition in Ghana is a multisectoral problem. The factors associated with average malnutrition rates are not necessarily the same as those associated with socioeconomic inequality in malnutrition.

Abstract: BACKGROUND: Although measuring socioeconomic inequality in population health indicators like infant mortality is important, more interesting for policy purposes is to try to explain infant mortality inequality. The objective of this paper is to quantify for the first time the determinants' contributions of socioeconomic inequality in infant mortality in Iran. METHODS: A nationally representative sample of 108 875 live births from October 1990 to September 1999 was selected. The data were taken from the Iranian Demographic and Health Survey (DHS) conducted in 2000. Households' socioeconomic status was measured using principal component analysis. The concentration index of infant mortality was used as our measure of socioeconomic inequality and decomposed into its determining factors. RESULTS: The largest contributions to inequality in infant mortality were owing to household economic status (36.2%) and mother's education (20.9%). Residency in rural/urban areas (13.9%), birth interval (13.0%), and hygienic status of toilet (11.9%) also proved important contributors to the measured inequality. CONCLUSIONS: The findings indicate that socioeconomic inequality in infant mortality in Iran is determined not only by health system functions but also by factors beyond the scope of health authorities and care delivery system. This implies that in addition to reducing inequalities in wealth and education, investments in water and sanitation infrastructure and programmes (especially in rural areas) are necessary to realize improvements of inequality in infant mortality across society. These findings can be instrumental for the recent 5 year Economic, Social and Cultural Development Plan of Iran, which identified the reduction of inequalities in social determinants of health.

Abstract: A study was conducted to determine the incidence of trypanosome infections in cattle in tsetse-free and tsetse-infested zones of the Amhara Region of northwest Ethiopia. A total of six sentinel herds were established and the cattle observed during a period of 8 consecutive months. The prevalence of seropositive cattle was high in both the tsetse-free and tsetse-infested zones. The average monthly incidence of trypanosome infection, determined using molecular diagnostic tools, was 20.9% and 25.7% in the tsetse-free and the tsetse-infested zones, respectively. In the tsetse-free, Trypanosoma vivax was responsible for 90.9% of the cattle trypanosome infections. In the tsetse-infested zone, Trypanosoma congolense and T. vivax contributed almost equally to the trypanosome infections in cattle. Trypanosome infection, regardless of species, resulted in anaemia as evidenced by a significant decrease in the packed cell volume of the infected animal. The outcome of this longitudinal study suggests that control of trypanosomiasis in the Amhara Region cannot be achieved by tsetse control alone. Supplemental measures to include drug therapy and biting fly control are discussed.

Abstract: East Coast fever (ECF), a tick-borne disease of cattle, is a major constraint to livestock development in Africa in general and southern Zambia in particular. Understanding the transmission patterns of this disease complex is very difficult as shown by previous studies in southern and eastern Zambia due to the interplay of risk factors. In this long-term study, we investigated whether global weather changes had any influence on disease transmission in traditionally kept cattle in southern Zambia. The results from this study show a strong association between increased Theileria parva contacts in cattle and the presence of El Niño, clearly linking a simple climatic index to disease outbreaks. We therefore propose that in southern Zambia, the simple and readily available multiple El Niño Southern oscillation index (MEI) ranks be used in planning ECF control programmes and early warning.

Abstract: Theileria parva sporozoite stabilates are used for immunizing cattle against East Coast fever and in in vitro sporozoite neutralization assays. In this study, we attempted to identify a cheaper freezing medium and quantified the infectivity loss of sporozoites due to refreezing of stabilates, using an in vitro technique. Pools of stabilates prepared using Minimum Essential Medium (MEM), Roswell Park Memorial Institute (RPMI 1640), foetal calf serum (FCS) and phosphate-buffered saline (PBS) were compared. All were supplemented with bovine serum albumin except the FCS. RPMI 1640 was as effective as MEM in maintaining sporozoite infectivity while the infectivity in PBS and FCS reached only 59% and 67%, respectively. In a second experiment, a stabiiate based on MEM was subjected to several freeze-thaw cycles including various holding times on ice between thawing and refreezing. Refrozen stabilate gave an average sporozoite infectivity loss of 35% per cycle. The results indicate that RPMI can be used as a cheaper freezing medium for T. parva stabilates and that refrozen stabilate doses need to be adjusted for the 35% loss of infectivity.

Abstract: The rate at which falciparum resistant malaria spreads in different transmission settings is still a controversial subject. We have assessed the spread of mutant Plasmodium falciparum parasites in six Ugandan populations with varying prevalence of chloroquine resistance (CQR), malaria transmission intensity, multiplicity of parasite clones and prevalence of CQ use. For each population, we have determined the wild and mutant allele frequency at codons 76 and 86 of the pfcrt and pfmdr1 genes, respectively. The highest frequency (median = 16.3%, range: 0.0-70.4%) of infections with two pure mutants (no wild genotype in either gene), adjusted for clone multiplicity, was observed at the extremes of malaria transmission intensity. The wild/mutant (W/M) allele ratio (an index for tracking the progression of CQR) was less than one in all sites (median = 0.51, range: 0.09-0.98) for the pfcrt-76 gene, while it was greater than one in two of six sites (median = 0.75, range: 0.4-1.6) for the pfmdr1-86 gene, suggesting that the pfcrt-76 mutants were the predominant parasites at all sites. Furthermore, the pfmdr1-86 W/M allele ratio was consistently higher than that of the pfcrt-76. The spread of mutations linked to CQR in P. falciparum commences with the pfcrt-76 gene mutations, followed later by the pfmdr1-86 gene mutations that modulate higher CQR. Such spread occurs faster at the extremes of the transmission spectrum and could explain why mathematical models have previously generated conflicting results with respect to malaria transmission intensity and spread of CQR.

Abstract: This paper presents statistical methodology to analyze longitudinal binary responses for which a sudden change in the response occurs in time. Probability plots, transition matrices, and change-point models and more advanced techniques such as generalized auto-regression models and hidden Markov chains are presented and applied on a study on the activity of Rhipicephalus appendiculatus, the major vector of Theileria parva, a fatal disease in cattle. This study presents individual measurements on female R. appendiculatus, which are terminating their diapause (resting status) and become active. Comprehending activity patterns is very important to better understand the ecology of R. appendiculatus. The model indicates that activity and non-activity act in an absorbing way meaning that once a tick becomes active it shows a tendency to remain active. The change-point model estimates that the sudden change in activity happens on December 10. The reaction of ticks on acceleration and changes in rainfall and temperature indicates that ticks can sense climatic changes. The study revealed the underlying not visually observable states during diapause development of the adult tick of R. appendiculatus. These states could be related to phases during the dynamic event of diapause development and post-diapause activity in R. appendiculatus.

Abstract: There were 118 cases of bovine spongiform encephalopathy (BSE) in Belgium before January 1, 2004. Trends in their age at detection were analysed and attempts were made to use this parameter as a predictor of the current status of the BSE epidemic in the country. The following variables were considered: date of birth, breed, date of detection, mode of detection, and the number and age of animals slaughtered and rendered each month. Age at detection as a function of date of birth was a very poor epidemiological indicator. It was concluded that the increasing age of BSE cases when they were detected was due to the depletion of cases, as a result of there being no new infections, and that it is a reliable indicator of a decrease in the epidemic curve in Belgium. By means of a simulation it is shown how age distribution at the time of detection closely follows the epidemic curve and data from Great Britain are used to illustrate the point.

Abstract: Studies sometimes estimate the prevalence of a disease from the results of one or more diagnostic tests that are applied to individuals of unknown disease status. This approach invariably means that, in the absence of a gold standard and without external constraints, more parameters must be estimated than the data permit. Two assumptions are regularly made in the literature, namely that the test characteristics (sensitivity and specificity) are constant over populations and the tests are conditionally independent given the true disease status. These assumptions have been criticized recently as being unrealistic. Nevertheless, to estimate the prevalence, some restrictions on the parameter estimates need to be imposed. We consider 2 types of restrictions: deterministic and probabilistic restrictions, the latter arising in a Bayesian framework when expert knowledge is available. Furthermore, we consider 2 possible parameterizations allowing incorporation of these restrictions. The first is an extension of the approach of Gardner et al and Dendukuri and Joseph to more than 2 diagnostic tests and assuming conditional dependence. We argue that this system of equations is difficult to combine with expert opinions. The second approach, based on conditional probabilities, looks more promising, and we develop this approach in a Bayesian context. To evaluate the combination of data with the (deterministic and probabilistic) constraints, we apply the recently developed Deviance Information Criterion and effective number of parameters estimated (pD) together with an appropriate Bayesian P value. We illustrate our approach using data collected in a study on the prevalence of porcine cysticercosis with verification from external data.

Abstract: Sero-epidemiological surveys involving 27,526 cattle over a period of 8 years show that Theileria parva, the parasite causing East Coast fever (ECF) is found throughout southern Zambia. Higher values of T. parva sero-prevalence were observed in the plateau districts of Monze, Choma and Mazabuka than in the valley districts of Siavonga and Sinazongwe. Our results reveal a strong association between high T. parva sero-prevalence and the presence of the periodic climatic phenomenon known as the El Nino Southern Oscillation. More T. parva sero-positive samples were recorded during El Nino years (1997/98) (P<0.001) than other years in the study period. From this association, we conclude that Multiple El Nino Southern Oscillation Indices can be used to predict years with high or low ECF infection prevalence thereby contributing to the improved control of ECF in the area.

Abstract: Two ixodid tick species, Rhipicephalus appendiculatus (Neumann) and Rhipicephalus zambeziensis (Walker et al.) (Acari: Ixodidae), both originating from the southern province of Zambia, were used to study the survival time of adults at a range of different humidities and temperatures. In general, the experiment clearly demonstrates the different survival times of the two species in relation to the climatic conditions tested: survival of R. zambeziensis was better under more extreme conditions of temperature and humidity. These findings offer an explanation for the different distribution ranges of the two tick species. Rhipicephalus appendiculatus is more confined to cooler and wetter conditions, whereas R. zambeziensis is adapted to hotter and drier areas.

Abstract: Short delays to treatment are important for the control of tuberculosis (TB). National Tuberculosis Programmes provide free diagnosis and treatment for smear-positive patients, so that the patients' out-of-pocket medical expenditure could be almost nil. The factors associated with delays in starting treatment, and the pre-treatment out-of-pocket medical expenditure for TB patients, have now been investigated in the Bolivian city of Cochabamba. Bolivia is the Latin American country with the highest incidence of TB. It is covered by a national TB programme that provides free diagnosis and free treatment for smear-positive patients. Structured interviews with 144 smear-positive patients enrolled in this programme revealed median patient, provider and total delays of 3.6, 6.2 and 12.9 weeks, respectively. The total delays were longer for the female patients than for the male, and for patients who consulted private doctors than for the other patients. When the first healthcare provider was a doctor, the median provider delay was 4.9 weeks in the public sector but 7.2 weeks in the private. The median out-of-pocket medical expenditure per patient, which was U.S.$13.2 overall, was much higher for those who consulted a private doctor than for those who did not (U.S.$21.9 v. U.S.$5.4, respectively; P<0.001). It appears that interventions targeting doctors (in both the private and public sectors) are likely to have a larger impact on the shortening of delays in TB treatment than interventions targeting patients. They could also reduce unnecessary out-of-pocket expenditure.

Abstract: OBJECTIVE: To measure the socioeconomic inequality in infant mortality in Iran (the Islamic Republic of Iran). METHODS: We analysed data from the provincially representative Demographic and Health Survey, which was done in Iran in 2000. We used a dichotomous hierarchical ordered probit model to develop an indicator of socioeconomic status of households. We assessed the inequality in infant mortality by using the odds ratio of infant mortality between the lowest and highest socioeconomic quintiles at both the provincial and national levels, and the concentration index, an inequality measure based on the entire socioeconomic distribution. RESULTS: We found a decreasing trend in the infant mortality rate in relation to socioeconomic quintiles. The poorest to richest odds ratio was 2.34 (95% CI = 1.78-3.09). The concentration index of infant mortality in Iran was -0.1789 (95% CI = -0.2193--0.1386). Furthermore, the inequality of infant mortality between the lowest and highest quintiles was significant and favoured the better-off in most of the provinces. However, this inequality varied between provinces. CONCLUSION: Socioeconomic inequality in infant mortality favours the better-off in the country as a whole and in most of its provinces, but the degree of this inequality varies between the provinces. As well as its national average, it is important to consider the provincial distribution of this indicator of population health.

Abstract: In Vietnam, a large proportion of all malaria cases and deaths occurs in the central mountainous and forested part of the country. Indeed, forest malaria, despite intensive control activities, is still a major problem which raises several questions about its dynamics.A large-scale malaria morbidity survey to measure malaria endemicity and identify important risk factors was carried out in 43 villages situated in a forested area of Ninh Thuan province, south central Vietnam. Four thousand three hundred and six randomly selected individuals, aged 10-60 years, participated in the survey. Rag Lays (86%), traditionally living in the forest and practising "slash and burn" cultivation represented the most common ethnic group. The overall parasite rate was 13.3% (range [0-42.3] while Plasmodium falciparum seroprevalence was 25.5% (range [2.1-75.6]). Mapping of these two variables showed a patchy distribution, suggesting that risk factors other than remoteness and forest proximity modulated the human-vector interactions. This was confirmed by the results of the multivariate-adjusted analysis, showing that forest work was a significant risk factor for malaria infection, further increased by staying in the forest overnight (OR= 2.86; 95%CI [1.62; 5.07]). Rag Lays had a higher risk of malaria infection, which inversely related to education level and socio-economic status. Women were less at risk than men (OR = 0.71; 95%CI [0.59; 0.86]), a possible consequence of different behaviour. This study confirms that malaria endemicity is still relatively high in this area and that the dynamics of transmission is constantly modulated by the behaviour of both humans and vectors. A well-targeted intervention reducing the "vector/forest worker" interaction, based on long-lasting insecticidal material, could be appropriate in this environment.

Abstract: Theileria parva sporozoite stabilates are used in the infection and treatment method of immunization, a widely accepted control option for East Coast fever in cattle. T. parva sporozoites are extracted from infected adult Rhipicephalus appendiculatus ticks either manually, using a pestle and a mortar, or by use of an electric homogenizer. A comparison of the two methods as a function of stabilate infectivity has never been documented. This study was designed to provide a quantitative comparison of stabilates produced by the two methods. The approach was to prepare batches of stabilate by both methods and then subject them to in vitro titration. Equivalence testing was then performed on the average effective doses (ED). The ratio of infective sporozoites yielded by the two methods was found to be 1.14 in favour of the manually ground stabilate with an upper limit of the 95% confidence interval equal to 1.3. We conclude that the choice of method rests more on costs, available infrastructure and standardization than on which method produces a richer sporozoite stabilate.

Abstract: This paper reports the investigation of risk factors for bovine herpesvirus-1-seropositivity, based on a cluster-sample survey of the Belgian cattle population. This serosurvey was carried out in 1998 in 309 randomly selected unvaccinated herds of all types (dairy, mixed and beef) were all bovids (N = 11,284) were sampled. Older and male cattle had higher seroprevalence. Origin (homebred or purchased) and herd size interacted; for smaller herds (< or = 50 cattle on the premises), purchase status and larger herd size were risk factors, whereas these effects were not observed for larger herds.

Abstract: BACKGROUND: Public-private partnerships are felt to be necessary for tuberculosis (TB) control in some developing countries. OBJECTIVES: To evaluate the potential of a collaboration between the National TB Programme (NTP) and private pharmacies in Bolivia, the country with the highest TB incidence in Latin America. METHODS: We contacted the local Pharmacists' Association in the city of Cochabamba, and designed a two phase intervention. The objectives of the first phase were to decrease the availability of TB drugs in private pharmacies on a voluntary basis, and to improve referral of clients seeking TB drugs to the NTP. A survey of all pharmacies allowed for a before-after comparison with a baseline survey. The objectives of the second phase were to obtain referral of pharmacy clients with chronic cough for TB screening in the NTP. This phase was started in 70 pharmacies and evaluated after 2 months using the referral slips issued by the pharmacists. RESULTS: The proportion of pharmacies selling TB drugs decreased (rifampicin: 23-11.5%; isoniazid: 16-3.1%; P<0.001) and the proportion of pharmacies referring to the NTP clients seeking TB drugs increased (22-58%; P<0.0001). In the second phase, 26 of 70 pharmacies (38%) referred a total of 41 clients for screening in the NTP (i.e. an average of 0.29 clients per pharmacy and per month); 11 of 41 (27%) were screened and three of 11 (27%) diagnosed with smear-positive TB. CONCLUSION: The first phase of the intervention proved effective in reducing the availability of the main TB drugs in pharmacies, and in improving referral of clients seeking TB drugs. Key factors in this success were not specific to Bolivia, and collaboration between private pharmacies and public services appears possible in that respect. However, collaboration with pharmacies does not seem an efficient way to increase the number of patients screened for TB, and to shorten delays to TB diagnosis and treatment.

Abstract: A longitudinal epidemiological survey of bovine trypanosomosis and its vectors was carried out in the Volta river basin of Northern Ghana to determine the relationship between cattle management and the incidence of bovine trypanosomosis. Two groups of sentinel cattle under different systems of management, classified as "fully-sedentary" and "partially-sedentary" (depending on the type of management) were followed over a 1-year period starting from March 2003 onwards. Cattle were screened at intervals of 3 months using the buffy coat technique (BCT). Buffy coat specimen from animals that were positive for the BCT and those that were negative, but with a packed cell volume (PCV) of less than 21% were further tested using the polymerase chain reaction (PCR). Plasma from all animals were tested for antibody using the indirect antibody enzyme-linked immunosorbent assay (ELISA). Trypanosomosis challenge was determined in tandem with the epidemiological survey with watering sites of sentinel cattle being the foci of interest. The parasitological prevalence at the start of the survey was higher in the fully-sedentary group (9%) than in the partially-sedentary group (3%). In subsequent visits, however, the parasitological incidence was consistently higher in the partially-sedentary group than in the fully-sedentary group. The mean seroprevalence (ELISA) of both groups increased from 3% in March to 54% in December. Statistical analysis of the serological results using a random effect logistic regression, showed a significant difference in incidence of bovine trypanosomosis between the two groups. There was also a significant effect of time. The influence of cattle herding on host-vector-parasite interface and its consequence on the incidence of trypanosomosis are discussed.

Abstract: Livestock keeping may have an important environmental impact. Therefore, there is a crucial need for understanding where and why livestock is kept in an urban context. In that frame, a survey was carried out in Ouagadougou (Burkina Faso) in 2002. The study documents the socio-economic determinants of urban livestock keeping in a semi-arid environment, its constraints and the underlying driving forces for keeping livestock in the city and the perception of the future by livestock keepers. The results show that 26.3% of the households in Ouagadougou are currently keeping livestock, including all major domestic animal species. The main motivation for keeping livestock in an urban setting is its’ generation of income. Main identified constraints are animal health problems, feed supply, theft, and manure management. A comparison with crop production highlights that the latter is practised by even poorer urban dwellers compared to pure livestock keepers. Technical, environmental and public health issues have to be resolved to secure sustainable urban development. (c) 2005 Elsevier Ltd. All rights reserved.

Abstract: Serological surveys using the schizont indirect fluorescence antibody test (IFAt) are routinely carried out to monitor the Theileria parva infection prevalence. The present study evaluates the diagnostic accuracy of the IFAt in eastern Zambia, where the transmission of T. parva is highly seasonal. The data set resulted from a sentinel herd (n = 105 animals) study carried out between 1995 and 2000 and was split into an epidemic period, during which the majority of the cattle became infected, and an endemic period with seasonal disease incidence in calves. In the epidemic period the T. parva seroprevalence followed closely the build up of the herd immunity. In the endemic period the seroprevalence fluctuates considerably although most of the animals had been infected. Overall, the diagnostic sensitivity of the IFA test was 55% at cut-off titre 1:40 and 28% at cut-off 1:160. The specificity of the test was 86 and 95%, respectively. A logistic regression model demonstrates that the sensitivity is significantly lower when the T. parva transmission is low (p < 0.01). The analysis of receiver operator characteristic curves classifies the test as moderately accurate (area under the curve, AUC = 0.79) during the epidemic period and less accurate in the endemic period (AUC = 0.63). Neonatal serology surveys yield a better estimate of the infection prevalence. The sensitivity of the neonatal test was 73% at cut-off titre 1:40 and 24% at cut-off 1:160.

Abstract: We examined the relationship between body size and the phenology of the tick complex Rhipicephalus appendiculatus/Rhipicephalus zambeziensis. These ticks transmit Theileria parva in cattle. In Africa, the body size of R. appendiculatus increases with latitude while the body size of the morphologically similar Rhipicephalus zambeziensis is constant at two different latitudes. A larger body size is necessary once survival becomes a constraint. The most plausible explanation for the smaller R. appendiculatus in equatorial Africa is the cost to produce a larger egg. The consequences of these findings for the introduction of R. appendiculatus in new environments are discussed. New field observations from southern Zambia indicate that R. appendiculatus body size does not vary seasonally as compared to eastern Zambia. This is an additional indication of the presence of a single diapausing population of larger ticks.

Abstract: Over the past 10 years, the Mekong Delta region in Vietnam has experienced fast socio-economic development with subsequent changes in malaria vectors ecology. We conducted a 2-year prospective community-based study in a coastal rural area in the southern Mekong Delta to re-assess the malaria epidemiological situation and the dynamics of transmission. The incidence rate of clinical malaria, established on 558 individuals followed for 23 months by active case detection and biannual cross-sectional surveys, was 2.6/100 person-years. Over the 2-year study period, the parasite rate and malaria seroprevalence (Plasmodium falciparum and P. vivax) decreased significantly from 2.4% to almost 0%. Passive case detection (PCD) of clinical cases and serological follow-up of newborns carried out in a larger population confirmed the low and decreasing trend of malaria transmission. The majority of fever cases were seen in the private sector and most were unnecessarily treated with antimalarials. Training and involvement of the private sector in detection of malaria cases would greatly improve the quality of health care and health information system.

Abstract: The susceptibility of tsetse flies (Diptera: Glossinidae), Glossina palpalis gambiensis (Vanderplank), and G. m. morsitans (Westwood) to topically applied spinosad, a mixture of insecticidal molecules from the actinomycete Saccharopolyspora spinosa, is almost as high as to deltamethrin. However, susceptibility to spinosad does not differ significantly between teneral and gravid flies, contrary to deltamethrin. Spinosad might be a promising candidate for future tsetse control by the sequential aerial technique.

Abstract: During a period of four consecutive years, trypanosomosis surveys were conducted in a tsetse-infested and tsetse-free area of the Amhara Region of north-west Ethiopia. In each study area randomly selected communal cattle were sampled and their blood was investigated using parasitological diagnostic methods. At the same time the population of biting flies was sampled. The monthly average prevalence of trypanosome infections in cattle did not differ significantly between study areas. In both study areas, the prevalence of trypanosome infections was highest during the long rainy season. Trypanosome infections were mainly due to Trypanosoma vivax and they significantly reduced the average packed cell volume and the body condition of the animals. The monthly prevalence of infection was correlated with the density of biting flies, such as Tabanidae and Stomoxys spp., in the preceding month suggesting an important role of mechanical transmission in the epidemiology of trypanosomosis in both areas.

Abstract: Several diagnostic techniques are used to estimate the prevalence of the zoonotic tapeworm Taenia solium in pigs, but none of these tests are perfect, making interpretation of results difficult. A Bayesian approach was used to estimate values for the prevalence and diagnostic test characteristic of porcine cysticercosis by combining results of four imperfect tests. Village pigs (N = 868) slaughtered in Lusaka (Zambia), were bled, and tongue and routine meat inspected; and serum antibody and parasite antigen concentrations were determined by ELISA. A model, based on a multinomial distribution and including all possible interactions between the individual tests required 31 parameters to be estimated, but actually allowed only 15 parameters (i.e. had 15 degrees of freedom) to be estimated. Therefore, prior expert opinion on specificity and (in)-dependence of the tests was entered in the model, resulting in a reduction of the number of parameters to be estimated. The estimated prevalence of porcine cysticercosis was 0.642 (95% confidence interval 0.54-0.91). The performances of the tests were (sensitivity (se)-specificity (sp)): tongue inspection (se 0.210-sp 1.000), meat inspection (se 0.221-sp 1.000), Ab-ELISA (se 0.358-sp 0.917), Ag-ELISA (se 0.867-sp 0.947). To validate the estimates obtained from the model we performed a second study: 65 randomly purchased Zambian village pigs were bled for serum antibody and antigen determination, their tongue and meat inspected; and in addition, the carcasses were dissected for total cysticercus counts (gold standard). Cysticerci were found in 31 pigs (prevalence 0.477, 95% confidence interval 0.35-0.60), overlapping with the estimated prevalence in the first study. Sensitivity and specificity values obtained for the aforementioned tests in this study were in agreement with those estimated. A Bayesian analysis framework offers the possibility to combine prior opinion with experimental data to more accurately estimate the real prevalence of porcine cysticercosis in the absence of a gold standard.

Abstract: Immunization against the protozoan Theileria parva by infection and treatment has proved to be very efficient for the control of East Coast fever, an acute and often-fatal lymphoproliferative tick-borne disease of cattle in Eastern, Central and Southern Africa. The immunizing dose of live T. parva sporozoites used in this method is usually determined by in vivo titration. An alternative in vitro method of quantification of sporozoites in whole tick-derived stabilates is proposed. The method consists of incubating serially diluted T. parva stabilates with bovine peripheral blood lymphocytes, the host cell that is infected naturally. Allowing the cultures to incubate undisturbed for the full cultivation period (10 days) reduced the variability among replicate titrations. Fungal contaminations were avoided by centrifuging stabilates at 400 g prior to the incubation, which did not precipitate sporozoites significantly. Fungistatics, Nystatin and Flucytosine, did not appear to interfere with the in vitro development of T. parva but their effect on fungal growth was limited. In vitro titration data were compared to in vivo infection data for 2 stabilates. In vitro titration of T. parva sporozoites should allow more ethical and efficient research on the preparation and storage of T. parva tick-derived stabilates.

Abstract: Reporting of clinically suspected cattle is currently the most common method for detecting cases of bovine spongiform encephalopathy (BSE). Improvement of clinical diagnosis and decision-making remains crucial. A comparison of clinical patterns, consisting of 25 signs, was made between all 30 BSE cases, confirmed in Belgium before October 2002, and 272 suspected cases that were subsequently determined to be histologically, immunohistochemically, and scrapie-associated-fiber negative. Seasonality in reporting suspected cases was observed, with more cases being reported during wintertime when animals were kept indoors. The median duration of illness was 30 days. The 10 most relevant signs of BSE were kicking in the milking parlor, hypersensitivity to touch and/or sound, head shyness, panic-stricken response, reluctance to enter in the milking parlor, abnormal ear movement or carriage, increased alertness behavior, reduced milk yield, teeth grinding, and temperament change. Ataxia did not appear to be a specific sign of BSE. A classification and regression tree was constructed by using the following four features: age of the animal, year of birth, number of relevant BSE signs noted, and number of clinical signs, typical for listeriosis, noted. The model had a sensitivity of 100% and a specificity of 85%. This approach allows the use of an interactive decision-support tool, based entirely on odds ratios, a statistic independent of disease prevalence.

Abstract: Forest malaria is a complex but common phenomenon occurring in southeast Asia. We studied its epidemiology through a prospective community-based study in central Vietnam. A total of 585 individuals were followed for two years by active case detection and biannual cross-sectional surveys. The prevalence of antibodies to Plasmodium falciparum was constantly about 20% across surveys and the incidence rate of clinical episodes of P. falciparum malaria was 0.11/person-year. Multivariate analysis showed that regular forest activity was the main risk factor for clinical malaria and malaria infections. Untreated bed nets had a significant protective effect (60%), except for people regularly sleeping in the forest. The population-attributable fraction for regular forest activity was estimated to be 53%. Our results confirm the major role played by forest activity on the malaria burden in this area and provide the basis for targeting control activities to forest workers. New interventions based on insecticide-treated materials need to be urgently evaluated.

Abstract: This study was aimed at the identification of location and household characteristics influencing the choice of keeping livestock or practising crop production in a post-conflict region in Central Africa. Two thousand eight hundred randomly selected families from Brazzaville (Congo) were surveyed. From these, 6% are both keeping livestock and producing crops, 3% are keeping livestock only, 24% are producing crops only and 67% are not producing crops nor keeping livestock. From these four groups, respectively, 135, 84, 246 and 245 households were interviewed to collect further data on household and location characteristics. Non-parametric and parametric techniques were compared as tools to analyse the groups. In the non-parametric classification tree method CART following variables were identified as being important for the engagement in keeping livestock or urban agriculture: keeping livestock before 1997, practising agriculture before 1997, property size, locality, income, availability of water, professional activity and level of instruction. Including surrogate variables resulted in extra variables: age, availability of electricity and sex. In the multinomial regression only the most important variables from the classification tree were withheld and other insights were obtained. The results of this research highlighted the shortcomings of multinomial regression. Fitting a full model containing all possible interactions becomes an impossible task with 20 explanatory variables. Using the classification tree information in a multinomial model appears the most appropriate solution, and this method is a useful tool for further work in the analysis of livestock and crop production systems. The importance of the historical component in the decision to practise crop production and keep livestock was demonstrated. Being involved in crop production develops roots, which cannot be destroyed by impediments such as periods of conflict.

Abstract: In vitro studies were focussed on the duration and cessation of merogony in Theileria parva infected blood lymphocyte cell cultures. The cultures were infected using purified tick stabilates as an alternative to in vitro infections, using sporozoites obtained by labour intensive dissections of salivary glands from infected ticks. After establishment of infection in peripheral blood lymphocytes (PBL), merozoites were temporarily produced for about 2 months after which lymphoblasts only contained schizonts.

Abstract: We studied the occurrence of human cysticercosis in 4993 individuals from three rural communities of Menoua Division, West Province of Cameroon. Circulating antigens of Taenia solium metacestodes were detected in 0.4%, 1.0% and 3.0% of the serum samples taken in Bafou, Bamendou and Fonakekeu, respectively, and examined using a monoclonal antibody-based enzyme-linked immunosorbent assay. This test detects only carriers of living cysticerci and gives thus a good idea of the presence of active cysticercosis. The percentage of persons infected with cysticercosis increased with age. Twenty-two of the 34 seropositives underwent computed tomography (CT) of the brain. Thirteen of them were CT-scan positive, which shows that neurocysticercosis was present in 59.1% of the tested seropositive persons. No living cysticerci were detected among 20 seronegative people. About 20.6% of the seropositives had a history of or current taeniasis against only 1.9% of the seronegatives. Based on these figures and on the data on porcine cysticercosis (prevalence: 11%) and human taeniasis (prevalence: 0.13%) collected in the same region, we conclude that T. solium cysticercosis is an endemic, but overlooked public health problem in West Cameroon.

Abstract: The number of malaria parasite clones per infection-multiplicity of parasite clones-is affected by the transmission intensity, multiplicity increases with increasing transmission. This affects the frequency of parasites' sexual recombination and, if several mutations in different genes are involved, can break down drug resistant genotypes. Therefore, the effects of malaria transmission intensity on the spread of drug resistance could vary depending on the number of genes involved. Here we show that, compared to low transmission, intermediate-high transmission is associated with a 20-100-fold lower risk for the mutations linked to chloroquine resistance and a 6-17 times higher risk for those linked to sulphadoxine-pyrimethamine resistance. This is consistent with the hypothesis of a multigenic basis for chloroquine resistance and a monogenic basis for that of sulphadoxine-pyrimethamine. Reducing transmission intensity could slow the spread of resistance. However, a reduction below a critical threshold (e.g. when parasite prevalence in children 2-9 years old is around 60-80%) could, paradoxically, accelerate the spread of resistance to chloroquine and possibly to other drug combinations whose basis is multigenic. Our findings have important implications for malaria control because increasing drug resistance has a substantial impact on mortality.

Abstract:

Abstract: During January 2002 the frequency of Taenia solium cysticercosis was studied in a series of 504 epileptic patients from 3 rural localities in the West and North-West provinces of Cameroon using an enzyme-linked immunosorbent assay for both circulating antigen (Ag-ELISA) and antibody (Ag-ELISA) detection. Taenia solium antigens were detected in the sera of 1.2% of the patients whereas specific antibodies against the parasite were present in 44.6% of the patients. Significantly less seropositive results in Ab-ELISA were recorded in Batibo than in Bandjoun and Bamendjou, whereas a borderline significant difference was recorded with increasing age. Furthermore, 56.2% of patients with late-onset epilepsy showed antibodies against cysticercosis. Taenia solium cysticercosis appears to be an important cause of epilepsy in Cameroon.

Abstract: This paper critically assesses the design implications for the analysis of surveys of infections. It indicates the danger of not accounting for the study design in the statistical investigation of risk factors. A stratified design often implies an increased precision while clustering of infection results in a decreased precision. Through pseudo-likelihood estimation and linearisation of the variance estimator, the design effects can be taken into account in the analysis. The intra-cluster-correlation can be investigated through a logistic random effect model and a generalised estimating equation (GEE), allowing the investigation of the extent of spread of infections in a herd (cluster). The advantage of using adaptive Gaussian quadrature in a logistic random effect model is discussed. Applicable software is briefly reviewed. The methods are illustrated with data from a bovine herpesvirus 1 (BHV-1) serosurvey of Belgian cattle.

Abstract: Three hundred and forty-six serum samples taken between 1998 and 2000 from urban stray cats in the city of Ghent were tested for antibodies to Toxoplasma gondii and feline immunodeficiency virus (FIV), and antigens of feline leukemia virus (FeLV). Of these 346 samples, 243 (70.2 per cent) were seropositive for Tgondii. Thirty-nine cats (11.3 per cent) had antibodies against FIV and 13 (3.8 per cent) had circulating antigens of FeLV. Fewer of the female cats had FIV and heavier cats had a higher seroprevalence of FIV. Exact logistic regression showed that cats that were infected with FIV were more likely to be infected with T gondii (P = 0.04), and the cats with FIV had a higher titre of Tgondii antibodies than FIV-negative animals. However, FeLV was not associated with either T gondii or FIV.

Abstract: Distribution data for epidemiologically important ticks (Acari: Ixodidae) in the Southern Province of Zambia, one of the main cattle areas of the country, are presented. Boophilus microplus (Canestrini) was not recorded in southern Zambia, whereas Boophilus decoloratus (Koch) is present throughout the area. New distribution patterns for less economically important ixodid ticks are also discussed. Southern Zambia is a transition zone because it is the most northern area in Africa where mixed Rhipicephalus appendiculatus Neumann and Rhipicephalus zambeziensis Walker, Norval & Corwin populations were reported. Although a second generation of adult R. appendiculatus/R. zamnbeziensis was encountered, simulations indicated that this phenomenon is very rare in southern Zambia, mainly because of the colder temperatures during the early dry season and lower rainfall. These simulations were supported by a development trial under experimental conditions. Tick body size measurements showed that southern Zambian ticks are larger than eastern Zambian R. appendiculatus. It is hypothesized that body size is related to diapausing intensity in this species. The epidemiological consequences are that a different approach to control Theileria parva (Theiler) (Piroplasmida: Theileriidae) and other tick-borne diseases is needed in southern Zambia, compared to the one adopted in eastern Zambia.

Abstract: Diapause in adults of the African brown ear tick Rhipicephalus appendiculatus is dependent on latitude and stock origin. Lower latitude populations, that is, those nearer the equator, show no diapause response to long or short day exposure. Diapause response to short daylengths is found in higher latitude populations, further south, and increases with increasing latitude. Nearly all individuals in the southen most population, used in this study, enter diapause under short and long day exposure which implies that the onset of diapause in this population is obligatory. Diapause termination in higher latitude populations is induced by increasing photoperiod, further north, but still south of the equator, diapause is terminated by ageing. The differences in diapausing behaviour of the different populations are discussed in relation to their climatic conditions.

Abstract: The methodology used to detect a polychlorinated biphenyl (PCB)/dioxin contamination in a Belgian cattle population that was not exposed to the PCB/dioxin incident in 1999 is presented. This population is directly or indirectly destined for human consumption. The methodology consisted in the systematic sampling of all calf-fattening stations and groups of cattle destined for export, and in the random sampling of slaughter cattle. This approach is compared to the method described in directive 96/23/CE from the European Council. When PCB concentrations exceeded the tolerance level of 0.2 micro g/g body fat (seven congeners with numbers 28, 52, 101, 118, 138, 153, and 180), dioxins (seventeen 2,3,7,8-substituted congeners of PCDD and PCDF) were also determined. The prevalence of Belgian slaughter cattle with PCB concentrations above this cutoff was 0.3% (95% confidence interval: 0.01-1.50%). Results indicate that the incidence of contamination was minimal, with environmental origin and common in all industrial countries. The maximal potential exposure of an adult human consumer to dioxins through diet of bovine origin is estimated in two worst-case scenarios. The first one corresponds to the consumption of contaminated food products by a small number of consumers during a long period (local consumption) and the second simulates the consumption of contaminated products by a large number of consumers during a short period (supermarket purchase). The theoretical maximum daily intake of dioxins in adults was respectively 374 and 123 pg TEQ/d. The estimated maximum increase of dioxin body burden corresponds to 7 pg TEQ/g fat in the local consumption scheme and 0.07 pg TEQ/g fat in the supermarket consumption scheme.

Abstract: Neospora caninum is a protozoan parasite, which causes fetal and neonatal mortality in livestock and companion animals. In 224 abortions in Belgian cattle, different diagnostic methods were used to demonstrate infection, and the presence of N. caninum. An indirect fluorescent antibody test (IFAT) was used to analyze fetal and maternal sera and immunohistochemistry (IHC) was performed when lesions consistent with neosporosis were observed in the brain, heart or liver. Twenty dairy cattle sera out of 70 (29%) and 13 beef cattle sera out of 93 (14%) were positive by IFAT. A positive titer to N. caninum was found in seven and three fetuses born to beef and dairy cows, respectively. Lesions consistent with N. caninum infection were observed in 17 fetuses. Of nine positive beef fetuses, five were confirmed by IHC while, all but one dairy fetus were confirmed using the same technique.Age had no influence on the serological status of the mother (P = 0.486) whereas husbandry system had a borderline influence (P = 0.082). However, a strong association (P = 0.004) between the level of antibodies in the dam and the occurrence of lesions in the fetus was observed and lesions were more prominent in dairy than in beef fetuses. Additionally, the distribution of intra-cerebral lesions was more extensive in dairy than in beef fetuses (P < 0.0001). Age and serological status of the fetus were found to influence the occurrence of lesions in beef fetuses (both P < 0.001) but no such significant relationships could be demonstrated in dairy fetuses. The study indicated that N. caninum must be considered as an important cause of bovine abortion in Belgium.

Abstract: To determine the prevalence of porcine cysticercosis, a survey was carried out in 27 villages belonging to two rural communities of West-Cameroon (Bafou and Bamendou). Between January and August, 2000, a total of 707 pigs were examined serologically and by tongue inspection. Serum samples were examined for circulating parasite antigen using a monoclonal antibody-based sandwich enzyme-linked-immunosorbent assay (Ag-ELISA) and for antibodies against cysticerci (Ab-ELISA). Seventy eight samples (11.0%) were found positive in the Ag-ELISA and 154 (21.8%) in the Ab-ELISA, while by tongue inspection on the same animals cysticerci were detected in 43 pigs (6.1%). Gibbs sampling using results of these three tests indicated that the estimated prevalence of porcine cysticercosis was 10.9%. Analysis of the Ag-ELISA results demonstrated that adult pigs showed a significantly higher seroprevalence (15%) than young ones (8.4%). There was no statistical difference in cysticercosis prevalence in pigs raised in households with or without a latrine. Animals that were reported to be usually confined were significantly less infected (9.9%) than free-roaming pigs (16.2%). Infection rates were significantly higher in pigs that had access to human faeces (13.8%) than those which did not have access (9.1%). This study has identified some community behavioural and environmental practices that should be modified to prevent continuous transmission of porcine cysticercosis.

Abstract: This paper presents the results of the follow-up of three sentinel herds between 1994 and 2000 during an East Coast fever (ECF) epidemic in eastern Zambia. The animals of the sentinel herds were closely monitored clinically and serologically together with detailed Rhipicephalus appendiculatus counts. Peaks of disease incidence occurred in the rainy season (December-February) and the dry months of May-July with nymph-to-adult tick transmission dominating the infection dynamics. A second wave of adult R. appendiculatus at the start of the dry season is essential for the occurrence of a full-blown epidemic while the size of the susceptible cattle population acts as a most important limiting factor. The majority of adult cattle of the sentinel herds became infected less than 2 years after the introduction of the disease. The median age at first contact for calves born towards the end of the study (1999) was about 6 months. The case-fatality ratio (including sub-clinical cases) is estimated at 60%. It is argued that part of the so-called 'natural mortality' is actually due to ECF and that ECF occurrence and mortality are systematically underestimated. The direct financial cost of the epidemic, based on loss of animals and cost of treatment only and calculated over 4 years running, is estimated at about 6 US dollars per year per animal at risk. The value of the traditional seroprevalence survey as a tool for monitoring ECF epidemiology is put in question and the prevalence of maternal antibodies in new-born calves, reflecting the immune status of the dam population, is introduced as an alternative. It is demonstrated that an efficient immunisation campaign should concentrate its efforts in the period of low adult R. appendiculatus abundance (July-October).

Abstract: A sero-epidemiological study of Taenia saginata cysticercosis was carried out in adult cattle in Zambia to determine the prevalence and study the influence of the farming system on the infection rate. Serum samples were examined for circulating parasite antigen by a monoclonal-based sandwich ELISA. Thirty-eight of 628 serum samples were found positive (prevalence 6.1%). Cysticercosis was significantly more prevalent in feedlots and in traditional farming systems than in dairy farms. It is suggested that the continuous man to animal contact and the use of casual workers in feedlots may be factors that are conductive to T. saginata transmission.

Abstract: An enzyme-linked immunosorbent assay (ELISA) for detecting circulating Taenia solium antigen was evaluated in Viet Nam; 12 of 210 people gave a positive result, including 5 persons with epilepsy. Cysticercosis was confirmed in 9 persons. Agreement between the ELISA, computerized tomography scanning and biopsy examination was high.

Abstract: The objective of this study was to determine the prevalence and importance of porcine cysticercosis in rural areas of Zambia. The study involved an abattoir survey of 1316 pigs at a slaughter slab in Lusaka and two field surveys in villages in Southern and Eastern provinces. Lingual examination of live pigs and visual inspection of their carcass as well as blood sampling for measuring circulating parasite antigen by enzyme-linked immunosorbent assay (Ag-ELISA) were used as parameters to measure infection. In the field surveys, a questionnaire was administered to every household whose pigs were examined to obtain information on pig husbandry practices and to study risk factors for the infection. Out of the 1316 pigs examined at the slaughter slab, 143 (10.9%) and 271 (20.6%) were positive by lingual examination and meat inspection, respectively. Most of the pigs were very heavily infected with predominantly live cysts. The field surveys revealed that eight (8.2%) out of 98 pigs from Southern province and eight (5.2%) out of 151 pigs from Eastern province were positive for cysticercosis by tongue palpation. Using the Ag-ELISA 20 (20.8%) and 14 (9.3%) pigs were positive in Southern and Eastern provinces, respectively. The questionnaire survey revealed poor pig husbandry practices, absence of meat inspection and control, poor knowledge of the disease and poor sanitation in the surveyed villages. The prevalence of pig cysticercosis found in this study ranks among the highest in the southern African region, in Africa and in the world. The current study suggests the presence of human tapeworm carriers and a high risk of human cysticercosis in the surveyed areas as well as in urban centres where pigs from rural areas are increasingly sold, slaughtered and consumed.

Abstract: The incidence of first contact with the protozoan Theileria parva was determined in two traditional cattle herds in the Southern Province of Zambia during a period of average rainfall in 1997 and 1998, following a drought in the previous two years. Compared to that period, there was a marked increase in the number of rainy season first contacts attributable to transmission by Rhipicephalus appendiceulatus adults. However, there were still more dry season contacts that resulted from nymphal transmission. These results highlight the important role that climate plays in the transmission of theileriosis in the Southern Province of Zambia.

Abstract: Leishmania infantum is the etiological agent of visceral (VL) and a cutaneous form (CL) of leishmaniasis around the Mediterranean Basin. In order to document the parasite genetic background corresponding to this clinical diversity, chromosome size polymorphism was analysed in 32 French isolates (18 CL and 14 VL) originating from the Cévennes and the Pyrénées Orientales (PO), and corresponding to zymodemes MON-1 and MON-29. Five chromosomes bearing tandemly repeated genes encoding for important antigens (gp63, PSA-2 and K39) or key metabolic functions (mini-exon and rDNA) were studied. Significant size variation (100-270 kbp) was observed for chromosomes bearing mini-exon, PSA-2 and rDNA genes, which involved variation in copy number of corresponding genes. The two other chromosomes showed smaller size-variation and did not involve dosage of gp63 and K39 genes. Chromosomal size showed correlation with geography and clinical origin: (i) chromosome 2 (mini-exon) was found to be significantly smaller in the PO; (ii) chromosomes 12 (PSA-2) and 27 (rDNA) were significantly smaller in the strictly cutaneous MON-29 isolates. Gene rearrangements and their synergistic effects on the phenotypic expression of the parasite are discussed.

Abstract: In a study of the prevalence and incidence of trypanosomosis in horses and donkeys in two regions of the Gambia, surveys were carried out at Niamina east and Bansang south with a high and low to moderate tsetse challenge, respectively. Eleven horses and 67 donkeys were sampled monthly from August 1997 to September 1998. Blood samples were examined for trypanosomes using the buffy-coat (BC) method and polymerase chain reaction (PCR). Three primer sets were used, specific for either Trypanosoma vivax (TVW), Trypanosoma congolense (GOL) or Trypanosoma brucei (ORPHON5J).The BC results showed that the prevalence (August 1997) and the average monthly incidence (September 1997-1998) of trypanosome infections in horses (45.5 and 16%, respectively) were significantly higher than in donkeys (6.2 and 9%, respectively). Using PCR, the number of detected cases was seven times higher than using the BC. T. congolense was the most frequently observed species, followed by T. vivax and T. brucei. This study confirms earlier observations by other authors that donkeys, which are exposed to a similar tsetse challenge as horses, are significantly less infected with trypanosomes than the latter.

Abstract: The incidence of first contact with the protozoan Theileria parva was determined in three traditional cattle herds in the Southern Province of Zambia in 1995 and 1996. The majority of first contacts occurred during the dry season in June, July and August, at a time of nymphal activity and in the absence of Rhipicephalus appendiculatus adults, indicating that larva to nymph transmission plays a more prominent role than nymph to adult transmission under the prevailing conditions.

Abstract: Newly-moulted adults of three Rhipicephalus appendiculatus stocks, originating from Kenya, Zambia and Zimbabwe, were kept in different photoperiods (12h:12h, 13h:11h and 14h:10h light:dark). The stock originating from Kenya showed almost no behavioural diapause in any of these day lengths, whereas virtually all individuals of the Zimbabwean stock entered a behavioural diapause irrespective of day length. Adults from the Eastern Province of Zambia, a transition zone between the multivoltine phenology in equatorial Africa and the univoltine in southern Africa, exhibited a photoperiod-dependent diapause response. The possible mechanisms of diapause regulation and their origin are discussed.

Abstract: Two trials were carried out in order to compare the prophylactic effect of a subcutaneously implanted sustained release device (SRD) containing a mixture of a biodegradable copolymer, poly(caprolactone-co-L-lactide), and isometamidium (ISMM) with that obtained after intramuscular injection of the drug. In a first experiment under controlled conditions, two groups of cattle were treated with 0.5 mg/kg isometamidium either as a SRD or intramuscularly (i.m.), and exposed at monthly intervals to Glossina morsitans morsitans infected with Trypanosoma congolense. The average protection period was at least 24 months in the SRD treated against 5.7 months in the i.m. treated group. Using an ISMM enzyme-linked immunosorbent assay, the drug could be detected until 140 days post-treatment in the latter group, whereas in the former group, traces of the drug were detectable until 330 days after treatment. Furthermore, a field trial was carried out at the Madina Diassa ranch in Mali involving three groups of N'Dama cattle, each containing 23 or 24 animals. Two groups were treated with 1 mg/kg ISMM either as a SRD or i.m. and a third group served as untreated control. Twelve months after treatment, the cumulative infection rates were 56.5, 87.8 and 91.6% in the SRD implanted, the i.m. treated and the control groups, respectively. The ISMM concentrations were slightly lower than in the laboratory trial, but the overall pattern of drug disappearance from the sera of the SRD treated cattle was very similar in both trials. Statistical analysis showed that the incidence of trypanosomiasis was significantly lower in the SRD treated than in the i.m. treated group.