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1.
OBJECTIVE: To estimate the prevalence of Mycobacterium avium subsp paratuberculosis infection among cows on beef operations in the United States. DESIGN: Cross-sectional seroprevalence study. Sample Population-A convenience sample of 380 herds in 21 states. PROCEDURES: Serum samples were obtained from 10,371 cows and tested for antibodies to M avium subsp paratuberculosis with a commercial ELISA. Producers were interviewed to collect data on herd management practices. RESULTS: 30 (7.9%) herds had 1 or more animals for which results of the ELISA were positive; 40 (0.4%) of the individual cow samples yielded positive results. None of the herd management practices studied were found to be associated with whether any animals in the herd would be positive for antibodies to M avium subsp paratuberculosis. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the prevalence of antibodies to M avium subsp paratuberculosis among beef cows in the United States is low. Herds with seropositive animals were widely distributed geographically.  相似文献   

2.
A simple random survey was conducted in Ireland during 2005 to estimate the ELISA-prevalence of paratuberculosis, commonly called Johne's disease (JD), in the cattle population. Serum samples were collected from all 20,322 females/breeding bulls over 12 months-of-age in 639 herds. All samples were tested using a commercially available absorbed ELISA. The overall prevalence of infected herds, based on the presence of at least one ELISA-positive animal, was 21.4% (95% CI 18.4%-24.9%). Herd prevalence levels amongst dairy herds (mean 31.5%; 95% CI: 24.6%, 39.3%) was higher than among beef herds (mean 17.9%; 95% CI: 14.6%-21.8%). However, the animal level prevalence was similar. The true prevalence among all animals tested, was calculated to be 2.86% (95%CI: 2.76, 2.97) and for animals >= 2 yrs, it was 3.30% (95%CI: 3.17, 3.43). For animals in beef herds, true prevalence was 3.09% (95%CI: 2.93, 3.24), and for those in dairy herds, 2.74% (95%CI: 2.59, 2.90). The majority of herds had only one ELISA-positive infected animal. Only 6.4% (95% CI 4.7%-8.7%) of all herds had more than one ELISA-positive infected animal; 13.3% (CI 8.7%-19.7%) of dairy herds ranging from two to eight ELISA-positive infected animals; and, 3.9% beef herds (CI 2.4%-6.2%) ranging from two to five ELISA-positive infected animals. The true prevalence of herds infected and shedding Mycobacterium avium subspecies paratuberculosis is estimated to be 9.5% for all herd types; 20.6% for dairy herds; and 7.6% for beef herds. If ELISA positive animals <2-years-of-age are excluded, the true herd prevalene reduces to: 9.3% for all herd types; 19.6% for dairy herds; and 6.3% for beef herds based on a test specificity (Sp) of 99.8% and test sensitivity (Se) (i.e., ability to detect culture-positive, infected animals shedding at any level) of 27.8-28.9%.  相似文献   

3.
The prevalence of Mycoplasma bovis infection in France was assessed by means of a serological survey of suckling beef cattle, using an ELISA. The survey included 824 randomly selected herds in eight French counties and a total of 32,197 animals more than one year old. In each county, the number of herds tested was determined statistically on the basis of the hypothesis that about 40 per cent of herds are infected. The proportion of herds containing at least one infected animal ranged from 28 to 90 per cent depending on the county. Among the 32,197 sera tested, the animal infection rate ranged between 2 per cent and 13 per cent. In infected herds, the average number of positive animals per herd was between 10 and 20 per cent, and the infection was unevenly distributed among the areas tested.  相似文献   

4.
Prior to establishing a control and prevention program for Johne's disease in cattle in Galicia (northwest Spain), a survey was conducted to estimate the prevalence of the disease. For this survey, 61,069 animals of at least 1-year of age from 2735 randomly selected herds were bled and samples analyzed with a commercial ELISA. The estimated true individual-level prevalences – assuming the manufacturer's reported test sensitivity of 48.5% and specificity of 98.9% – were 3.02% in dairy cattle, 1.03% in beef cattle and 2.83% in animals from farms with both dairy and beef cattle. True herd prevalences (with herds declared positive if one or more animals tested positive) were 10.69% for dairy herds, 0% for beef herds and 2.71% for mixed herds. When herds were declared positive if at least two animals tested positive, true herd prevalences were 14.75% for dairy herds, 1.47% for beef herds and 12.01% for mixed herds. Assuming a higher specificity of 99.4%, true individual-level prevalences increased to 4.03% in dairy herds, 2.07% in beef herds and 3.84% in mixed herds. Herd prevalences were 27.77%/18.79%, 2.78%/2.40% and 5.70%/12.24% (using the one/two-animal cut-offs) in dairy, beef and mixed herds, respectively. In conclusion, these results seem to indicate that a small percentage of cows and a rather high percentage of dairy herds in this region are MAP-seropositive.  相似文献   

5.
A province-wide cross-sectional seroprevalence and agroecological risk factor study of Mycobacterium avium subspecies paratuberculosis (MAP) and Neospora caninum (NC) infection among cattle in 100 cow-calf herds in Alberta was conducted. The seroprevalence of MAP in adult cattle was 1.5% across all herds. Using a widely accepted herd test cutpoint of 2 or more seropositive cows out of 30 animals tested, 7.9% of herds were estimated to be infected (95% confidence interval (CI): 2.3-23.4%). Seroprevalence of MAP differed by agroecological region; specifically, cattle and herds in areas with high soil pH (> 7.0), southern latitudes, and arid climates had a moderately reduced risk of infection (P < 0.10). Seroprevalence of NC infection was 9.7% among adult beef cattle province-wide--these levels also varied by agroecological region--with 91.0% of herds infected overall.  相似文献   

6.
In herds with known prevalence (P) use of environmental sampling (ES) to detect Mycobacterium avium ssp. paratuberculosis (MAP) infected cattle herds was proofed in relation to P. In 31 MAP-infected free stall dairy herds and 15 non-infected herds P was defined by annually repeated whole herd testing by fecal culture (34 877 individual samples). Eight infected herds had a very low (> 0-2%), 14 a low (> 2-5%), four a medium (> 5-10%), and five a high P (> 10%). A mean number of nine environmental samples per herd were collected from the floor of lactating cows, milking, calving and sick cow areas and the crossover to the calf area. After twelve weeks cultivation on HEYM-medium with and without mycobactin positive samples were further characterized by PCR. All non-infected herds (100%) showed negative and 22 (71%) of the infected herds positive results in ES. Nine infected herds with negative ES results had a low P (0.04-4,04%). Proportion of positive ES depended on P and on sampling areas with 53.3% positive results in lactating cow areas and 45.2% in milking areas. For P > 5%, ES in these two areas caused a positive herd status; herds with P < 5% required sampling in the other areas too. The ES method has a herd sensitivity of 87% for dairy herds with P > 2% and provides an efficient tool to determine MAP infection status or herd prevalence.  相似文献   

7.
The sensitivity and specificity of the ELISA and fecal culture tests for paratuberculosis in dairy cattle are examined. ELISA and fecal culture data from seven dairy herds where both fecal cultures and ELISA testing was done concurrently are included. A cohort of 954 cattle including 697 parturient adults, cultured every 6 months from 10 herds followed over 4 years served as the basis to determine fecal culture sensitivity. The fecal culture technique utilized a 2g sample with centrifugation and double incubation. Of the 954 cattle cohort of all ages (calf to adult) that were fecal sampled on the first herd visit, 79 were culture positive. An additional 131 animals were detected as culture positive over the next seven tests at 6-month intervals. The sensitivity of fecal culture to detect infected cattle on the first sampling was 38%. Of the 697 parturient cattle cohort, 67 were positive on the first fecal culture, while an additional 91 adult cattle were culture positive over the next seven tests, resulting in a sensitivity of 42% on the first culture of the total animals identified as culture positive. Animals culled from the herds prior to being detected as infected and animals always fecal culture negative with culture positive tissues at slaughter are not included in the calculations. Both groups of infected cattle will lower the apparent sensitivity of fecal culture. Infected dairy herds tested concurrently with both fecal culture and ELISA usually resulted in more than twofold positive animals by culture compared to ELISA.The classification of infected cattle by the extent of shedding of Mycobacterium paratuberculosis in the feces helps define the relative proportion of cattle in each group and therefore the likelihood of detection by the ELISA test. ELISA has a higher sensitivity in animals with a heavier bacterial load, i.e. high shedders (75%) compared to low shedders (15%). Repeated testing of infected herds identifies a higher proportion of low shedders which are more likely to be ELISA negative. Thus, the sensitivity of the ELISA test decreases with repeated herd testing over time, since heavy shedders will be culled first from the herds.  相似文献   

8.
A stochastic simulation model was developed to assess the risk of introduction of Mycobacterium avium subsp. paratuberculosis infection into a dairy herd through purchase of female replacement cattle. The effects of infection prevalence in the source herd(s), number of females purchased, and testing by enzyme-linked immunosorbent assay (ELISA) alone or ELISA and fecal culture as risk mitigation strategies were evaluated. Decisions about negative test results were made on a lot and individual basis. A hypothetical dairy herd, free from M. a. paratuberculosis, which replaced 1 lot (10, 30, or 100) of cows per year, was considered. Probability distributions were specified for the sensitivities and specificities of ELISA and fecal culture, the proportion of infected herds and within-herd prevalence for randomly selected replacement source herds (high prevalence) and herds in level 2 (medium prevalence) and level 3 (low prevalence) of the Voluntary Johne's Disease Herd Status Program (VJDHSP). Simulation results predicted that 1-56% of the lots had at least 1 M. a. paratuberculosis-infected cow. Assuming that ELISA sensitivity was 25%, simulation results showed on a lot basis that between 0.4% and 18% and between 0.1% and 9% were predicted to have at least 1 infected cow not detected by ELISA and by a combination of ELISA and fecal culture, respectively. On an individual cow basis, between 0.1% and 8.3% of ELISA-negative cattle in ELISA-positive lots were estimated to be infected. In both the lot and individual analyses, the probability of nondetection increased with larger lot sizes and greater prevalence. Sensitivity analysis indicated that the effect of a lower ELISA sensitivity (10%) was a variable decrease in mean detection probabilities for all combinations of prevalence and lot size. The benefit of testing introduced cattle with ELISA alone or in combination with fecal culture was found to be minimal if cows were purchased from known, low-prevalence (level 3) herds. The value of testing by ELISA alone or in combination with fecal culture was greatest in high-prevalence herds for all lot sizes. Testing of random-source cattle, bought as herd replacements, can partially mitigate the risk of introduction of M. a. paratuberculosis but not as well as by using low-prevalence source herds (level-3 VJDHSP), with or without testing.  相似文献   

9.
A cross-sectional study was performed to determine the odds of having a positive paratuberculosis ELISA result if the dam was ELISA positive in Texas beef cattle, adjusted for individual and herd-level risk factors for seropositivity. Texas beef cattle (n = 2,621) were tested for paratuberculosis by using a commercial ELISA and microbiologic culture of feces for Mycobacterium avium subsp. paratuberculosis (MAP). Pedigree data were collected to identify dam-and sire-offspring pairs. Bayesian mixed-effects logistic regression was used to estimate the odds of seropositivity associated with age, dam ELISA status, sire ELISA status, herd size, herd history of clinical paratuberculosis, within-herd seroprevalence, within-herd fecal MAP prevalence, and within-herd fecal non-MAP Mycobacterium spp. prevalence. Herd of residence was included as a random effect to account for the correlation of observations within the same herd. Statistically probable associations were observed between ELISA status and herd fecal MAP prevalence [OR (odds ratio) 1.28 per 1% increase; P < 0.001] and herd seroprevalence (OR 1.21 per 1% increase; P < 0.001). The association with dam ELISA status was small (OR 1.35) and not highly probable (P = 0.69). Results indicate that use of dam ELISA status to make culling decisions in beef cattle may not improve the success of paratuberculosis control programs. Alternative strategies may be more effective for reducing the odds of seropositivity.  相似文献   

10.
The results of a commercial bulk-milk enzyme-linked immunosorbent assay (ELISA) test for herd-level bovine leukemia virus (BLV) status were compared to results obtained from individual agar-gel immunodiffussion (AGID) testing on sampled cattle. A positive herd was defined as a herd having one or more AGID-positive animals. The estimated true herd status was based on the sensitivity and specificity of the AGID test and the number of cattle sampled per herd. Ninety-seven herds were used, with a mean of 13 cows sampled per herd. The AGID test indicated an apparent herd prevalence of 70.1%. After accounting for the number of cows sampled and the sensitivity and specificity of the AGID test, the estimated true herd prevalence of BLV was 52.3%. The ELISA test identified 79.4% of herds as positive for BLV, and had an apparent sensitivity and specificity of 0.97 and 0.62, respectively. However, after accounting for the sensitivity and specificity of the AGID test in individual animals, the specificity of the ELISA test was 0.44. The ELISA test was useful for identifying BLV-negative herds (i.e., ruling out the presence of BLV infection in test negative herds). With the moderately low specificity, herds identified as positive by the ELISA test would require further testing at the individual or herd level to definitively establish their BLV status.  相似文献   

11.
Kang YJ  Jo JO  Cho MK  Yu HS  Cha HJ  Ock MS 《Veterinary parasitology》2012,186(3-4):480-485
A serological survey for Neospora caninum and Besnoitia besnoiti was carried out in beef and dairy cattle in South Australia. Serum samples of dairy cattle (n=133) from 9 properties and tank milk samples from a further 122 dairy herds were tested. An additional 810 sera from beef cattle from 51 properties were also tested. Testing at the individual animal level by IDEXX NEOSPORA X2 Ab test ELISA revealed a low prevalence of N. caninum antibodies of only 2.7% (95% CI; 1.6-3.7%) sera positive, as did the milk testing that showed 2.5% (95% CI; 1.4-3.6%) of tank milks being positive. At the herd level, 29.4% (95% CI; 16.9-41.9%) of beef, and 44.4% (95% CI; 12.0-76.9%) of dairy cattle herds showed serum antibodies. The highest within-herd prevalence in beef was 20% and 25%in dairy, which explains the low herd prevalence in dairy detected by bulk milk testing. Testing for B. besnoiti antibodies by PrioCHECK(?) Besnoitia Ab 2.0 ELISA initially identified 18.4% (95% CI: 15.8-21.0%) of 869 individual cattle sera as positive by ELISA at the manufacturer's suggested cut-off threshold (15 PP). Additional tests by immunoblot and IFAT, however, could not confirm any of the ELISA results. The use of a higher (40 PP) threshold in the ELISA is suggested to improve specificity. There is thus no evidence of B. besnoiti infection in South Australian cattle.  相似文献   

12.
ABSTRACT

Aims: To investigate the seroprevalence of infection with bovine viral diarrhoea (BVD) virus among 75 beef herds and seroconversion in cattle during early pregnancy, and to determine the practices and opinions of farmers towards BVD control and their association with real and perceived herd serological status.

Methods: Blood samples were collected before mating in 75 beef herds across New Zealand from 15 unvaccinated heifers that had delivered their first calf that season. Serum samples were tested for BVD antibodies using ELISA individually, and after pooling samples for each farm. Animals that were antibody-negative were retested at either pregnancy diagnosis or weaning. Farmers were asked to complete a detailed survey about herd demographics, BVD testing and vaccination practices, and opinions towards national BVD control.

Results: Based on the pooled serum antibody ELISA results, there were 28/75 (37%) negative herds, 15/75 (20%) suspect herds, and 32/75 (43%) positive herds. Of 1,117 animals sampled 729 (65.3%) tested negative for BVD virus antibodies; when retested, 47/589 (8.0%) animals from 13/55 (24%) herds had seroconverted. Among 71 famers providing survey responses 11 (15%) believed their herd was infected with BVD, 24 (34%) were unsure and 36 (51%) did not think their herd was infected. Only 19/71 (18%) farmers had performed any BVD testing within the past 5 years and 50/70 (71%) had not vaccinated any cattle for BVD. Support for national BVD eradication programme was strong in 51/71 (56%) respondents, but the biggest challenge to BVD control was considered to be famer compliance. Compared to farmers who did not think their herd was infected, more farmers who thought BVD was present in their herds had previously tested for BVD, would consider testing all replacement calves, and would support establishing a national BVD database; fewer would consider purchasing BVD tested or vaccinated cattle only.

Conclusions and clinical relevance: Only 15% of the beef farmers in this study believed their herds were infected with BVD virus and few of them had undertaken BVD screening. Nevertheless many were supportive of implementing a national BVD control programme. It is likely that the lack of farmer awareness around BVD and the failure of farmers to recognise the potential impacts in their herds are hindering progress in controlling the disease in New Zealand. There are opportunities for New Zealand veterinarians to be more proactive in helping beef farmers explore BVD management options.  相似文献   

13.
The purpose of this study was to survey the seroprevalence of infection with the agents of production-limiting diseases in dairy cattle in New Brunswick, Nova Scotia, and Prince Edward Island. In 30 randomly selected herds per province, 30 cattle per herd were randomly selected and tested for antibodies to bovine leukemia virus (BLV) and Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis), while 5 unvaccinated cattle over 6 months of age were tested for antibodies to bovine viral diarrhea virus (BVDV). For BLV, 20.8% (15.8% to 27.0%) of cows were positive, and 70.0% (60.3% to 79.7%) of herds had at least one positive cow. In BLV-positive herds, the average BLV prevalence was 30.9% (24.8% to 37.2%). For M. paratuberculosis, 2.6% (1.8% to 3.9%) of cows were positive, and 16.7% (8.8% to 24.5%) of herds had at least 2 M. paratuberculosis-positive cows. In M. paratuberculosis-positive herds, the average M. paratuberculosis prevalence was 8.5% (6.9% to 10.1%). For BVDV, 46.1% (35.5% to 56.7%) of herds had at least 1 BVDV-positive animal with a titer greater than or equal to 1:64.  相似文献   

14.
The national bovine paratuberculosis (PTB) seroprevalence (apparent prevalence) in the Belgian cattle population was determined by a serological survey that was conducted from December 1997 to March 1998. In a random sample of herds (N=556, 9.5%), all adult cattle of 24 months of age or older (N=13,317, 0.4%) were tested for the presence of antibodies using a commercially available absorbed ELISA test kit. The PTB median within-herd seroprevalence (proportion of detected animals within the seropositive herds) and the PTB individual-animal seroprevalence (proportion of detected animals) were, respectively, 2.9% (quartiles=1.6-5.6) and 0.87% (95% confidence interval (CI)=0.71-1.03). The PTB herd seroprevalence (proportion of detected herds) was 18% (95% CI=14-21).Assuming a test sensitivity and specificity of 45 and 99% [Sweeney et al., 1995. J. Vet. Diagn. Invest. 7 (4), 488; Sockett et al., 1992. J. Clin. Microbiol. 30 (5), 1134], respectively, the median true within-herd prevalence and the true individual-animal were estimated to be 7 and 2%, respectively. The true herd prevalence of Mycobacterium paratuberculosis infection was first estimated according to currently accepted methodology. This calculation revealed that the specificity of the used test has a dramatic effect on the estimation; assuming a test sensitivity of 45% and a true within-herd prevalence of 7%, the true herd prevalence estimation decreased from 36 to 0.8% if the test specificity decreased from 99. 9 to 99%, respectively. This sensitivity analysis showed that the practical limits of the accuracy of the used screening test jeopardize the estimation of the true herd prevalence within reasonable confidence limits, because the within-herd PTB true prevalence was low.For this reason we augmented the herd specificity for herds with larger adult herd size (>5). This was done by increasing the cut-off number of positive cattle required (>/=2) to classify a herd truly positive and including herds with one positive test result if there was historical evidence of PTB (previous diagnosis and/or clinical signs). This approach resulted in an estimated true herd prevalence of M. paratuberculosis infection of 6%. The true herd prevalence for dairy, mixed and beef herds was, respectively, 10, 11 and 3%.  相似文献   

15.
Epidemiologic investigations of Salmonella infections in dairy cattle often rely on testing fecal samples from individual animals or samples from other farm sources to determine herd infection status. The objectives of this project were to evaluate the effect of sampling frequency on Salmonella isolation and to compare Salmonella isolation and serogroup classification among sample sources on 12 US dairy farms sampled weekly for 7-8 weeks. Three herds per state were enrolled from Michigan, Minnesota, New York and Wisconsin based upon predefined herd-size criteria. Weekly samples were obtained from cattle, bulk tank milk, milk filters, water and feed sources and environmental sites. Samples were submitted to a central laboratory for isolation of Salmonella using standard laboratory procedures. The herd average number of cattle fecal samples collected ranged from 26 to 58 per week. Salmonella was isolated from 9.3% of 4049 fecal samples collected from cattle and 12.9% of 811 samples from other sources. Serogroup C1 was found in more than half of the samples and multiple serogroups were identified among isolates from the same samples and farms. The percentage of herd visits with at least one Salmonella isolate from cattle fecal samples increased with overall herd prevalence of fecal shedding. Only the three herds with an average fecal shedding prevalence of more than 15% had over 85% of weekly visits with at least one positive fecal sample. The prevalence of fecal shedding from different groups of cattle varied widely among herds showing that herds with infected cattle may be classified incorrectly if only one age group is tested. Testing environmental sample sources was more efficient for identifying infected premises than using individual cattle fecal samples.  相似文献   

16.
Protothecosis is a severe form of mastitis in dairy cows caused by colorless algae of the genus Prototheca. Since P. zopfii is highly resistant to all known chemotherapeutics, infected cows must be removed from the herd. Eradication measures are difficult since many chronically infected cows may become intermittent shedders. Therefore, cultural methods are insufficient for control measures. In order to eradicate Prototheca zopfii-mastitis in dairy cattle herds, two isotype specific indirect ELISA for detection of IgA and IgG1 in whey were used in a dairy herd highly affected with protothecal mastitis. All cows (n = 313) were tested four times in intervals of six months. Milk specimens were examined in parallel by cultivation and serologically using two indirect ELISA systems for specific IgA and IgG1 in whey. Cows tested Prototheca positive were consequently separated from the herd and slaughtered. At the first examination, 15.6% of the animals were found positive by culture, and 23.3% were positive in at least one of the ELISA systems. Within two years, protothecal prevalence and incidence decreased to zero indicating that the eradication strategy used was successful. In summary, serological identification of P. zopfii-infected lactating cows is an useful tool to eradicate protothecal bovine mastitis in infected herds.  相似文献   

17.
OBJECTIVE: To evaluate sensitivities at the herd level of test strategies used in the Voluntary Johne's Disease Herd Status Program (VJDHSP) and alternative test strategies for detecting dairy cattle herds infected with Mycobacterium paratuberculosis. DESIGN: Nonrandom cross-sectional study. SAMPLE POPULATION: 64 dairy herds from Pennsylvania, Minnesota, Colorado, Ohio, and Wisconsin. Fifty-six herds had at least 1 cow shedding M. paratuberculosis in feces; the other 8 herds were free from paratuberculosis. PROCEDURE: For all adult cows in each herd, serum samples were tested for antibodies to M. paratuberculosis with an ELISA, and fecal samples were submitted for bacterial culture for M. paratuberculosis. Sensitivities at the herd level (probability of detecting infected herd) of various testing strategies were then evaluated. RESULTS: Sensitivity at the herd level of the testing strategy used in level 1 of the VJDHSP (use of the ELISA to test samples from 30 cows followed by confirmatory bacterial culture of feces from cows with positive ELISA result) ranged from 33 to 84% for infected herds, depending on percentage of cows in the herd with positive bacterial culture results. If follow-up bacterial culture was not used to confirm positive ELISA results, sensitivity ranged from 70 to 93%, but probability of identifying uninfected herds as infected was 89%. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the testing strategy used in the VJDHSP will fail to identify as infected most dairy herds with a low prevalence of paratuberculosis. A higher percentage of infected herds was detected if follow-up bacterial culture was not used, but this test strategy was associated with a high probability of misclassifying uninfected herds.  相似文献   

18.
Johne's disease is a well recognized problem in dairy herds. Relatively little information is available on either the prevalence or the control of Johne's disease in commercial cow-calf operations. In the fall of 1999, blood samples were collected during pregnancy testing from cows on community pastures in Saskatchewan. Sera from these cows were analyzed using a commercial ELISA for antibodies to Mycoplasma avium subspecies paratuberculosis. All cows from each herd examined at the community pastures were sampled. Of the 1799 samples tested, 15 had sample to positive (S/P) ratios greater than 0.25 and were considered positive (apparent sample prevalence, 0.8%; 95% CI, 0.4% to 1.5%). If we assume test sensitivity of 25% and specificity of 98% as recommended by the National Johne's Working Group, the true sample prevalence is not significantly different from 0.0%. The ELISA S/P results for the antibody test-positive animals ranged from 0.27 to 2.5. If a herd was classified as positive based on one test-positive animal, the average herd apparent prevalence was 15.2% (95% CI, 7.1% to 28.6%). If the potential for false-positive results was considered with 2 or more positive animals being required for positive herd status, the herd prevalence was 3.0% (95% CI, 0.4% to 13.4%). Because of the very low prevalence in cow-calf herds, future research to identify risk factors and control points should target problem herds and utilize a case-control study design.  相似文献   

19.
In Switzerland clinical bovine paratuberculosis is registered sporadically with on average seven outbreaks per year. Our present studies are aimed to investigate the prevalence of Mycobacterium avium ssp. paratuberculosis (MAP)-infections in the Swiss cattle population and, therefore methods to culture MAP from bovine feces as well as a commercially available ELISA to detect MAP-specific antibodies are evaluated by using fecal samples and blood sera from herds with cases of clinical paratuberculosis. A series of molecular methods i.e. PCR-coupled RFLP analysis of the IS1311-insertion element of M. avium, PCR-coupled RFLP-analysis of the mycobacterial rpoB-gene, and DNA analysis of the mycobacterial 16S rRNA gene are used to identify mycobacterial isolates grown from bovine feces. Up to now, MAP was detected by culture in 12 of 155 (7.7%) animals from herds with paratuberculosis. A rather striking result is the finding of atypical mycobacteria in feces of 75 cattle (48.3%). Among these isolates, M. avium ssp. avium, M. thermoresistibile, and M. hassiacum/M. buckleii have been identified so far.  相似文献   

20.
Three chronically paratuberculosis infected herds were tested for six years twice a year (intradermal Johnin test, antibody ELISA (IDEXX Corp.), microbial culture) according to a sanitary program. Culling of shedding animals and vaccination of calves with NEOPARASEC (Merial Corp.) were part of the program. In course of experiment, 1015 samples of 228 non vaccinated cows and 1502 samples of 293 vaccinated cattle have been tested. 3.8% of the vaccinated animals proved positive in microbial culture. Nearly all vaccinated calves developed granulomas sized from hazelnut to loaf at the injection site. Positive reactions in intradermal test as well as in antibody ELISA were found in very young calves. 24.3%, 33.7%, 25.9%, respectively of the non vaccinated animals were identified as shedders of M. avium subsp. paratuberculosis (MAP) by microbial culture. In the first and in the second herd most shedders of MAP were found in the first herd examination (66.7%, 42.9%, respectively), whereas in the third herd they were detected in the fifth examination (31.0%). At the beginning, 17.9% of non vaccinated animals proved positive in intradermal test, 14.4% in antibody ELISA. Afterwards, the number of positive test results decreased but increased again towards the end of the experiment. 48.5% of the 66 shedders showed positive reactions in intradermal test, 57.6% in antibody ELISA, 77.3% in at least one of these both tests. Antibodies in ELISA were found in rising frequency from two years before the time of shedding. 50.0% of the shedders reacted positive in ELISA at the time of shedding. In selected shedders first positive results were found at the age of about two years. Unfortunately, only incomplete hygienic measures were realized by the farmers. Under field conditions the realisation of attending sanitary programs is difficult. MAP is spread mainly by buying of animals, therefore a certification program for paratuberculosis free herds is urgently necessary as well as an improvement of diagnostic methods.  相似文献   

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