Abstract: Risk assessments relating to food safety over more than one step along a production chain are frequently hampered by lack of detailed quantitative data. This study set out to develop a Bayesian hidden variable model to integrate available limited data of the combined occurrence of three bacterial pathogens, Listeria monocytogenes, Yersinia enterocolitica and Yersinia pseudotuberculosis,
with causal assumptions along three steps of pork production chain. The pathogen occurrence data were animal specific both on conventional and organic pig farms and at the abattoir, but merely farm specific at meat cutting plants. The model was able to incorporate all data concerning different types of testing at different steps of the chain, and missing data values were dealt with in a straightforward manner. It provides a tool for quantitative risk assessments and for estimating the causal risk mitigation effects by combining external data with the specific follow-up data. Intervention effects are provided with Bayesian credible intervals indicating the uncertainty due to all information sources included in
the model. Combined prevalence in Finnish pork was estimated to be 1–11% and it could be reduced to 0–2% if head was removed intact and rectum sealed off.
Abstract: We report a multiplatform real-time polymerase chain reaction methodology based on genes encoding for the regulatory toxR activator and enterotoxin A protein to determine enterotoxigenic Vibrio cholerae types from other vibrios. This assay, which was successfully validated on a collection of 87 bacterial strains, including 63 representatives of V. cholerae and 8 noncholera vibrios provides a rapid tool for detection and identification of cholera.
Abstract: After billions of years of evolution and untold numbers of bacterial generations there appears to be only a finite number of genera belonging mainly to order Actinomycetales, producing largely similar types of antibiotics all over the world. It is hypothesized that this not just a result of limited number of susceptible targets or a transitory situation in the evolutionary process. It is proposed that there is some stabilizing factor associated with the commonly encountered antibiotics that alleviates the selection pressure to design new antibiotics. Synergistically acting molecules, an antibiotic and a component preventing the action of resistance mechanism is one way to stabilise the situation; perhaps the best known example of this is beta-lactam antibiotics and clavulanic acid. However, it is considered possible that during the extremely long evolution the Actinomycetes have also come up with metabolites preventing the actual development of resistance. These kinds of compounds, used along with antibiotics, could perhaps significantly reduce the ever-increasing threat of resistance among pathogens. This appears to be an unexplored area.
Abstract: Epidemiological investigations implicated the semen of artificial insemination (ai) bulls as the only plausible source of infection with bovine viral diarrhoea virus (bvdv) in 10 Finnish dairy herds. The infection was traced back to two northern Finncattle bulls that had been transiently infected when their semen had been collected while they were in a gene bank herd containing persistently infected (pi) animals. The isolates of bvdv from the animals in the gene bank herd, from the semen of the two bulls and from a pi calf born in one of the herds using the semen belonged to a rare genetic type in Finland and, on the basis of the nucleotide sequences in the 5' untranslated region, were identical. Cross-contamination of batches of semen at the ai station and an external source of bvdv were ruled out for the recipient herds. It was concluded that bvdv infection can be transmitted through the semen of transiently infected bulls under field conditions.
Abstract: The use of food industry by-products for feeding is restricted by European Union by-product regulation (1774/2002). However, the actual public health risks involved in the use of such products are poorly recognized. This study focuses on bovine milk rejected at the dairy because of a positive result in antimicrobial drug testing and thereafter used as feed for finisher pigs in Finland. In theory, this current practice could expose pork consumers to antimicrobial drug residues. Raw bulk milk samples originating from rejected lots were analysed with a multiresidue method detecting five beta-lactams, including benzylpenicillin. Based on the probabilistic simulation model developed, concentrations of benzylpenicillin in pork invariably remained below 1% of the maximum residue limit. Therefore, the use of this by-product as feed with the current practice was considered to pose only a negligible risk to consumers of pork products.
Abstract: Official vaccine sales statistics, the development of the young dog population and the takes of available vaccines were used to calculate the vaccine coverage and herd immunity (HI) against canine distemper, endemic during 1990-1993 and epidemic in 1994-1995 in Finland. Despite the satisfactory vaccine coverage, HI was no more than 50-65% in 1990-1993 because low-take vaccines dominated the market. Replacement of the low-take with high-take vaccines in 1995 raised the HI to 90%, which coincided with the ending of the epidemic. In 1996, the HI was slightly above 70%, which was sufficient to control the disease despite infectious pressure caused by repeated imports.
Abstract: BACKGROUND: Infectious bovine rhinotracheitis/infectious pustular vulvovaginitis (IBR/IPV) is a significant disease among domestic and wild cattle. The BHV-1 infection was first detected in Finland in 1970; presumably it was imported in 1968. The infection reappeared in the large-scale bulk-tank milk surveillances which started in 1990, and was eradicated in 1994. Our aim is to describe the epidemiology of this infection in Finland, and its eradication. MATERIALS AND METHODS: The official sources of pertinent information, the legal basis for the disease control and the serological methods for the detection of the infection are described. RESULTS AND CONCLUSION: Ten AI bulls were found to be seropositive in 1970-1971. The total number of herds with BHV-1 antibody positive animals in the large-scale surveillance in 1990 and subsequent epidemiological investigations in 1991 was five, and the total number of seropositive animals was 90. The five herds formed three epidemiological units; semen of at least one bull seropositive in 1971 had been used in each unit. This remained the only plausible route of infection in each of the three units. Using the 'test and slaughter' approach and total stamping out in one herd the infection was eradicated in 1994.
Abstract: The bovine viral diarrhoea virus (BVDV) situation among dairy herds and suckler-cow herds was monitored annually from 1998 to 2004. Bulk-tank milk (BTM) samples from all dairy herds and serum samples from beef animals at slaughter were examined for BVDV antibodies using a commercial indirect ELISA test. New BTM antibody-positive herds and herds with a history of BTM antibodies, but previously untested were sampled individually and tested for evidence of BVDV. The reason for the antibody-positivity or the source of infection was investigated. The percentage of BTM antibody-positive herds ranged from 0.45% in 2000 to 0.15% in 2003. The number of herds with persistently infected (PI) animals ranged from 10 in 2001 to 0 in 2003. The most common cause for a herd to become BTM antibody-positive was the purchase of a seropositive animal or a PI animal or a dam carrying a PI fetus. The new BVD decree of 2004 will be described in brief.
Abstract: An automated turbidimetric method was developed for group level identification of penicillinase sensitive penicillins, tetracyclines and fluoroquinolones in kidney samples. A sample pretreatment procedure was elaborated for the extraction of incurred residues from kidney tissue in a translucent solution to enable the measurement of changes in optical density. The method was comprised of three pairs, one for each antibiotic group: a sensitive test bacterium strain and a resistant strain for the identification of fluoroquinolones and tetracyclines, and a sensitive strain with and without penicillinase for the identification of penicillinase sensitive penicillins. The algorithm employed compared the areas under the OD vs. time curves; threshold values and experimentally observed intra-test criteria were also included in the algorithm. Antibiotics were reliably identified to group level, and no false identifications were obtained with antibiotics belonging to groups not included in the reference panel. Incurred penicillin G, oxytetracycline and enrofloxacin-ciprofloxacin residues were identified at or below the MRL levels for kidney tissue. The graphically determined shortest possible identification times varied between 2 and 7 h. The method developed could furthermore easily be diversified to include other antibiotic groups by adding new "sensitive-resistant" bacterium and medium combinations.
Abstract: Enzootic bovine leukosis (EBL) was recognized among Finnish cattle in 1966. Administrative decisions specifying and refining official control measures were given in 1966, 1976, 1980, and 1993. The measures' key principle always has been 'test and slaughter'. The EBL/bovine leukosis virus (BLV) infection situation was monitored at meat inspection, and hematologically between 1970 and 1977 and serologically between 1978 and 1989. Annual surveys including all dairy herds and samples from beef animals were conducted in 1990-2001. Bulk-tank milk samples represented the dairy herds in the surveys; the beef animals were sampled individually at slaughter. The maximum positive herd-level percentage in the surveys was 0.03%. EBL/BLV infection was evenly dispersed in the southern part of the country and nonexistent in the northern part. We conclude that herd-level prevalence of EBL/BLV infection never exceeded 5%. It nevertheless took 30 years to eradicate the disease and the infection. EBL was eradicated from mainland Finland in 1996 and from the island district of Ahvenanmaa in 1999. Annual monitoring of the EBL situation continues.
Abstract: An indirect conductimetric screening method using three test bacterium-medium combinations was developed for rapid detection of antibiotic residues in bovine carcasses. The detection time (DT), i.e. the point when the growth of the test bacterium was detected, was determined by observing the rate of change in the conductance plotted against time. This detection time averaged half of the reference time recorded by the instrument software. Total change in conductance (TC) was used as a further measure of growth. Threshold values for DT and TC were determined with inhibitor-free kidney samples. The presence of a residue was indicated if the DT exceeded the respective threshold value and was confirmed if the TC remained below the TC threshold value. The limits of detection (LODs) determined with fortified samples were at about or below the MRLs for cephalexin, chlortetracycline, ciprofloxacin, dihydrostreptomycin, enrofloxacin, oxytetracycline and penicillin G. The LODs for penicillin G, oxytetracycline and the sum of enrofloxacin and ciprofloxacin were also estimated with incurred samples; these samples were also analysed using liquid chromatography. The LODs determined with fortified and incurred samples were in close agreement. Given its rapid detection, good sensitivity to a wide range of antibiotics and ease of performance, the indirect conductimetric method developed here would seem to offer an appealing alternative to agar diffusion tests.
Abstract: A microbiological method was developed for group level identification of antibiotics in incurred kidney and muscle samples from cattle and pigs. The method was composed of six test bacterium-plate growth medium combinations and the result was recorded as a profile of growth inhibition zones. The sample profiles were compared to two sets of references: one constructed with standard antibiotic solution profiles, and the other with these combined with profiles of microbiologically and chemically identified residues from incurred samples. The algorithm employed in profile comparison located the minimal sum of absolute pairwise differences over the tests, with the addition of a number of experimentally observed intra-test criteria. Chemical identification and quantitation of incurred residues was based on liquid chromatography. The method identified penicillin G as a penicillinase sensitive penicillin, enrofloxacin and ciprofloxacin belonging to fluoroquinolone group, and oxytetracycline belonging to tetracycline group. Each of these residues was microbiologically identified below the Maximum Residue Limit (MRL) for kidney tissue. Combining sample profiles with the standard reference data set did not enhance the resolution. Microbiological and chemical identification test results were in good agreement. The results of this study show that a microbiological identification method is a useful tool in preliminary characterisation of antibiotic residues in animal tissues.
Abstract: The sheep disease maedi-visna (MV) was introduced into Finland in 1981 and had spread to eight flocks in the southwestern part of the country when first detected in a survey in 1994. Six more seropositive flocks were subsequently traced, bringing the total to 14. MV has a notifiable disease status in Finland that provides for official restrictive measures to which all infected herds are subject. These measures are withdrawn once the seropositive animals and their progeny are culled and the flock has showed negative signs in the test done twice, or after total culling. A voluntary control programme was initiated in January 1995 to extend official control efforts. The programme furnishes a guideline for culling, restrictions on contacts, and a timetable for testing the flock to attain MV-free status. Seven flocks of the 14 were slaughtered either immediately or after a period under restrictive measures. One flock finished sheep production after four years under restrictive measures. Selective culling and repeated testing was attempted with the other six flocks, three of which attained MV-free status. One flock finished sheep production after two years in the control programme, the other two dropped out of the programme when the restrictive measures were withdrawn. It was concluded that the control programme was salient in eradicating MV from Finland and that serological monitoring of the situation must be continuous.
Abstract: The associations between the levels of canine distemper virus neutralising antibodies and vaccination history, age and gender were investigated in a cross-sectional study of a sample of 4627 dogs from the Finnish urban dog population. Dogs vaccinated with either Canlan (Langford Laboratories) or Dohyvac (Solvay Animal Health) or with both, had significantly lower titres than those vaccinated with Candur (Behringwerke), Duramune (Fort Dodge Laboratories) or Nobivac (Intervet), or with combinations including at least one of these. The vaccines were classified as having low and high immunogenicity on the basis of the geometric mean titre achieved by the vaccine when compared with the geometric mean titre of the entire dataset. The low geometric mean titre of Canlan, Dohyvac and their combination groups resulted from the large proportion of dogs without detectable titres, especially dogs under one year of age, rather than from uniformly low titres. An age-stratified comparison of vaccine usage and titres showed that the division of the vaccines into low and high immunogenicity vaccines was apparent in the dogs less than two years of age but not in the older dogs. The first vaccination with the high immunogenicity vaccines resulted in a higher proportion of dogs with detectable antibodies than even repeated vaccination with the low immunogenicity vaccines. Neither the time elapsed since the most recent vaccination nor the gender of the dogs was associated with the titre of antibody.
Abstract: Bulk milk samples from every herd supplying milk to dairies in Finland were examined for the presence of antibodies to BVD virus (BVDV) annually during 1993-1997. The highest prevalence, 0.99% in 1994, declined to 0.37% in 1996; however, this favourable trend appeared to discontinue in 1997, where the prevalence remained at 0.41%. In 1993, sera of all individual animals from bulk milk antibody-positive herds were examined for the presence of these antibodies. Since 1994, only sera of animals from herds with a bulk milk absorbance reading greater than 0.250 in the EIA test were examined individually. Three geographic foci of BVDV antibody-positive dairy herds were resolved in 1994, one in the north-western, another in the eastern and a diffuse third in the southern part of Finland. A distinct limiting of the spread was apparent in 1997. Beef cattle were also studied during 1993-1997; in 1993 breeding units, in 1994 mainly beef suckler herds and in 1995-1997 serum samples of beef animals at slaughter were examined for the presence of antibodies to BVDV. The prevalence of seropositive herds in 1993 and 1994 was 30.2% and 3.2%, respectively, while the prevalence among slaughter animals ranged 0.8-1.6%. Seronegative animals in herds with > 50% of seropositive animals were examined for the presence of BVD-virus. A total of 40 dairy herds and two beef herds with viraemic (persistently infected, PI) animals was encountered during 1993-1997. A comprehensive control programme and a more specific, cooperatively funded eradication programme for dairy cattle were launched in 1994. These programmes most probably contributed to the decline in prevalence during 1994-1996.
Abstract: A survey for antibodies to maedi-visna virus (MV) in the Finnish sheep surveillance flocks was conducted in 1994. Examination of a total of 12931 serum samples from animals over 1 year of age from 545 flocks (81% of all flocks) revealed eight seropositive flocks and the subsequent epidemiological investigation yielded one additional seropositive flock, indicating a low prevalence of 1.6%. The infection was very probably imported from Sweden in 1981, but it was not detected until the survey was conducted 13 years later. The entire primary infection flock was slaughtered in 1995. 77% of the sheep were seropositive but the animals were clinically healthy and only one (5%) of the contact flocks of the primary infection flock had contracted the infection. This secondary infection flock, 77% of which was seropositive, was slaughtered in 1994; however, animals in this flock had respiratory problems and the lungs of three sheep showed typical MV lesions. Seven (24%) of its contact flocks had contracted the infection and these each had one or two seropositive animals except for one flock which had seven (18%) seropositive animals. The results show that the initial spread of MV can be insidious and wide before infection is revealed in surveys or any clinical cases are encountered.
Abstract: Canine distemper reappeared in dogs in Finland in 1990 after a 16-year absence. In 1994 to 1995 an outbreak occurred in areas with a high density dog population which involved dogs vaccinated against distemper. The estimated total number of cases was at least 5000, and 865 cases were confirmed by indirect fluorescent antibody testing of 3649 epithelial cell samples. The signs recorded by veterinary clinicians ranged from conjunctivitis, pyrexia and anorexia to signs of respiratory and gastrointestinal illness, with an estimated mortality of 30 per cent. Of the confirmed cases 631 (73 per cent) were between three and 24 months of age; 487 of these had been vaccinated at least once and 351 (41 per cent) had a complete vaccination history. Of these 351 fully vaccinated animals the proportion of dogs vaccinated with the most popular vaccine was significantly higher than would have been expected by its market share. In total, 4676 serum samples were collected from healthy vaccinated dogs during the peak and decline of the outbreak and tested for the presence of virus neutralising antibodies. The decrease in the proportion of young dogs with antibody titres < 1/8 coincided with the decline and end of the outbreak during the spring and summer of 1995. It was concluded that a critical decrease in the population's immunity during 1990 to 1994 was a major reason for the outbreak in the summer of 1994 and that the ultimate test for vaccines is an outbreak of disease.
Abstract: The growth of Yersinia enterocolitica O:3 was tested in an in vitro model of the porcine intestine at the physiological temperature of 39 degrees C of growing pigs. The model supported a stable population of Y. enterocolitica at a level 10(8)-10(9) cells ml-1. Plasmid profile analysis and the Ca(2+)-dependent proportion of the population suggested that the great majority of the Y. enterocolitica population retained the 70 kb virulence plasmid, pYV, throughout the experimental period of 5 d. The growth of Y. enterocolitica was substantially inhibited by the ileal and the caecal flora compared to the growth of the bacterium alone. Yersinia enterocolitica was not isolated after 3 d of cultivation.
Abstract: Lactobacillus acidophilus was isolated from washed and homogenized walls of the crop and caecum of an adult fowl. A strain that adhered well in the Fuller adhesion test was subcultured until colonies on Lactobacillus Selective agar changed from rough to smooth. This coincided with a change from aggregate to planktonic growth in liquid medium and a marked loss of ability to adhere. ultrastructure of cells from both types of culture was studied by electron microscopy. An S-layer formed the outermost part of the cell wall in the strongly-adherent strain, whereas this layer was covered with polymerized material or was absent in strains that lacked the ability to adhere, or those with reduced adherence.
Abstract: An in vitro intermittent-flow model was developed for studying bacterial interactions in the avian caecum. The model provides a closer simulation of caecal conditions than others described previously but does not require elaborate instrumentation. In preliminary trials, growth of caecal bacteria from an adult chicken was shown to be inhibitory to both Salmonella infantis and entero-haemorrhagic Escherichia coli.
Abstract: The origin of the competitive exclusion (CE) concept in controlling a Salmonella infantis outbreak in poultry in 1971 and the subsequent development of a commercial treatment product are described. The possible role of CE in salmonella control, current status of the concept and theories relating to the bacteria involved and mechanisms of protection are reviewed. Some observations are made on the need for methodological development and possibilities for extending the scope of CE to other pathogens and types of domestic animal.
Abstract: 1. The recommended dose of a commercial competitive exclusion (CE) product (BROILACT) was given orally to newly-hatched broiler chicks to protect them against oral challenge by Salmonella enteritidis PT4. 2. In 5 replicate trials, half of the birds thus treated and half from untreated control groups were examined for salmonellas at 5 d and the other half at 12 d after challenge. 3. Caecal contents were examined quantitatively while heart, liver and spleen samples were examined qualitatively by enrichment. 4. The treatment effectively prevented both colonisation of the caeca and invasion of the other organs by S. enteritidis PT4; the average number of salmonellas was less than 10 colony forming units (cfu)/g of caecal contents in the treated birds and more than 10 million cfu/g in the untreated birds. 5. Infection of organs other than the caeca was completely prevented by protective treatment, whereas 38% of the untreated birds were still infected at the end of the trial.
Abstract: 1. Control by competitive exclusion of intestinal colonisation by Salmonella infantis was studied in domestic chicks and turkey poults given a commercial product developed for use with chickens, compared with two similar preparations containing intestinal microorganisms from turkeys. 2. Each type of material protected both avian species when given orally before challenge; the degree of protection depended at least as much on the type of preparation as its host origin.
Abstract: Poultry production is under strict official control in Finland. Fifteen years after the introduction of 'competitive exclusion' treatment the majority of growers (over 70%) use it routinely. The number of Salmonella-positive flocks is less than 5% and the incidence of Salmonella-contaminated broiler carcasses has been 5-11% in the last two years. The average number of Salmonella cells on contaminated carcasses is very low, generally less than 5 per carcass. Between 70 and 80% of human Salmonella infections are contracted abroad, mainly outside the Nordic countries. It is estimated that only 15-20% of some 1200 cases of domestic origin are caused by contaminated poultry.
Abstract: The competitive exclusion (CE) product (Broilact) which is effective against Salmonellas, was found to be inactive against campylobacters. Microecological concepts were applied in the search of a new competitive flora and two novel strains ('K-bacteria') were isolated. These strains resembled campylobacters but differed from them in morphology, enzyme profiles (API), cellular fatty acid profiles and when tested with a ribosomal RNA hybridization probe (Gene-Trak). Two-week laboratory trials on broiler chickens showed that CE treatment may protect the birds against campylobacters but revealed the need for facultatively anaerobic bacteria in establishing a protective flora. A 5-week pilot scale trial was carried out. The trial involved 1800 newly hatched chicks in 30 groups. K-bacteria and Broilact, which provided the necessary facultatively anaerobic bacteria, were administered to some of the birds in the first drinking water. A seeder bird technique was used to challenge experimental and control birds with Campylobacter jejuni biotype 2 (broiler origin). Three seeder birds were placed in each group of 60 birds. Groups were sampled weekly for campylobacters and finally at the slaughterhouse. From each group, the caecal contents of two birds were examined quantitatively for campylobacters. The performance of the birds was also monitored during the trial. The results showed a 1.5 week delay in the onset of campylobacter infection in treated chicks and a consistently lower level of colonization in comparison with control birds. At slaughter, levels of carriage in caecal contents of treated birds were 1.5-2.0 log10 units lower than those of controls, despite apparent stress from harvesting and transportation. The treatment had no economically important effects on the performance of the birds during rearing.
Abstract: The competitive exclusion (CE) concept has been tested against both non-invasive and invasive salmonella serotypes. Studies with different challenge models indicate that CE treatment is likely to protect the young bird against all serotypes that are capable of intestinal colonization. Spray or 'droplet' application of the CE-treatment material was compared with administration in the first drinking water. Both methods gave a similar degree of protection against Salmonella infantis. A study was made to compare protection of newly hatched chicks and turkey poults by the one commercial CE product Broilact, and two similar preparations involving intestinal microorganisms from an adult turkey. Each preparation protected both avian species when administered orally prior to challenge, but the degree of protection obtained varied with the type of preparation and its host origin.
Abstract: 1. The efficacy of a commercial competitive exclusion (CE) product, BROILACT, was tested in pilot-scale trials involving groups of 100 broiler chicks. 2. Each group was challenged with Salmonella infantis through contact with infected seeder birds and numbers of salmonellae in the caecal contents were determined weekly. 3. The performance of the birds was also monitored over a 5-week period. 4. The results showed a gradual decline of the infection, even in the untreated groups, and a dose-dependent response to treatment. 5. The treatment had no significant effect on the performance of the birds.
Notes: Reprinted in 2008:
Control and eradication of viral diseases of ruminants. Official and Voluntary Measures. Verlag Dr. Müller, Saarbrücken Germany, ISBN: 978-3-639-09160-1
