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PubMed1981

Effects of physiol and chemical factors on the viability of Mycobacterium paratuberculosis.

Alternative methods of storing bovine fecal specimens for delayed culture of Mycobacterium paratuberculosis was studied. Significant (P less than 0.05) losses of viability were sustained by storage at 23 degrees C for 10 days and by treatment with 0.03 Zephiran for 4 and 10 days. Losses were moderate after storage at -70 degrees C for 15 weeks but significant (P greater than 0.05) after storage at 23 degrees C for 4 days. The alternative methods were compared with the standard method of processing specimens upon receipt and after 2 days in transit. Fecal specimens from 18 cattle were cultured.

Animals↗
PubMed2004

The distribution of Mycobacterium avium ssp. paratuberculosis in the environment surrounding Minnesota dairy farms.

The objective of this study was to characterize the distribution of Mycobacterium paratuberculosis (Map) in the environment of infected and uninfected Minnesota dairy farms. Eighty herds known to be infected from Minnesota's Johne's Disease Control Program (JDCP) and 28 herds known to be uninfected from Minnesota Voluntary Johne's Disease Herd Status Program (VJDHSP) were sampled. Fecal samples from up to 100 cows in each herd were cultured in pools of 5 cows. Two environmental samples were obtained from each farm from various locations. All samples were tested using bacterial culture for Map. Eighty percent of the JDCP herds had at least one positive pool. Environmental samples were cultured positive in 78% of the JDCP herds. Two (7%) of the VJDHSP herds had one positive pool, and one herd had one positive environmental sample. Environmental samples were cultured positive in cow alleyways (77% of the herds), manure storage (68%), calving area (21%), sick cow pen (18%), water runoff (6%), and postweaned calves areas (3%). There was an association between maximum level of colonies per tube from cow alleyways and manure storage and fecal pool prevalence. Herds with both areas cultured negative were estimated to have 0.3 to 4% fecal pool prevalence. Herds with both areas having a heavy load of bacteria were estimated to have 53 to 73% fecal pool prevalence. The study results indicate that targeted sampling of cow alleyways and manure storage areas appears to be an alternative strategy for herd screening and Johne's infection status assessment and for estimating herd fecal prevalence.

Animals↗
PubMed2001

Crohn's disease and Mycobacterium avium subsp. paratuberculosis: current issues.

Crohn's disease is a chronic debilitating inflammatory bowel disease of unknown etiology. Proposed causes include bacterial or viral infection, diet or exposure to tobacco smoke, genetic abnormality, and immune dysfunction. The bacterium Mycobacterium avium subsp. paratuberculosis (Map) has received much research attention as a potential cause of the disease. Map causes Johne's disease in ruminants. The pathology of Johne's disease superficially resembles that of Crohn's disease in humans. Some researchers have shown evidence of Map in intestinal tissues of Crohn's disease patients. Studies are in progress to investigate the possibility that Map exists in milk from infected cows and survives pasteurization. This is a controversial subject with the potential for media attention and public outcry. We examined the current literature and concluded that insufficient evidence exists at this time to implicate any one factor, including Map in milk, as the definitive cause of Crohn's disease. The high degree of uncertainty in this issue requires regulators to recognize the need for effective risk communication as ongoing research provides additional information about the disease.

Animals↗
PubMed2003

Evaluation of an absorbed ELISA and an agar-gel immuno-diffusion test for ovine paratuberculosis in sheep in Australia.

The sensitivities and specificities of an absorbed enzyme-linked immunosorbent assay (ELISA) and an agar-gel immuno-diffusion (AGID) test for the detection of Johne's disease in sheep were estimated using data from six known infected and 12 assumed uninfected sheep flocks. Sensitivities were estimated for all histologically positive sheep, as well as by histological lesion score, lesion type (paucibacillary or multibacillary) and sheep body-condition score, with ELISA sensitivities estimated at 95 and 99% specificity. Logistic-regression analysis was used to test for significant effects of lesion score and condition score, with flock included in the model as a random effect. Estimated specificities were 95% (95% CI: 93.4, 95.6%) and 99% (98.4, 99.4%) for ELISA cut-point ratios of 2.4 and 3.6, respectively, and 100% (99.7, 100.0%) for the AGID. Estimated sensitivities for all infected sheep were 41.5% (35.0, 48.3%), 21.9% (16.6, 27.9%) and 24.6% (19.1, 30.7%) for ELISA cut-point ratios of 2.4 and 3.6 and for AGID, respectively. Sensitivities of all tests and cut-points varied significantly between flocks and between categories of lesion score and condition score. Sensitivity ranged from 25 to 73, 10 to 47 and 9.2 to 63% between flocks, for the ELISA with cut-points of 2.4 and 3.6, and for the AGID, respectively. Sensitivity was highest in thin sheep and in sheep with multibacillary lesions. The effects of lesion type and condition score on test sensitivity were significant in the logistic regressions for the AGID and ELISA at both cut-points and the flock effect was significant for the AGID but not for the ELISA at either cut-point.

Animals↗
PubMed2004

Evaluation of a LAM ELISA for diagnosis of paratuberculosis in sheep and goats.

A milk and serum ELISA containing lipoarabinomanan (LAM) antigen was evaluated in sheep and goats versus agar gel immunodiffusion (AGID) test and polymerase chain reaction (PCR) using milk and lymph nodes. Milk and serum samples were obtained from six, two, and four flocks with unknown, negative and positive status of infection, respectively. By comparison of serum ELISA activity and PCR results, the positive and negative predictive values were calculated. Receiver operation characteristic (ROC) analysis was used for calculating the specificity and sensitivity at different cut-offs.

Animals↗
PubMed2002

Sensitivity and specificity of pooled faecal culture and serology as flock-screening tests for detection of ovine paratuberculosis in Australia.

The flock-level sensitivity of pooled faecal culture and serological testing using AGID for the detection of ovine Johne's disease-infected flocks were estimated using non-gold-standard methods. The two tests were compared in an extensive field trial in 296 flocks in New South Wales during 1998. In each flock, a sample of sheep was selected and tested for ovine Johne's disease using both the AGID and pooled faecal culture. The flock-specificity of pooled faecal culture also was estimated from results of surveillance and market-assurance testing in New South Wales. The overall flock-sensitivity of pooled faecal culture was 92% (95% CI: 82.4 and 97.4%) compared to 61% (50.5 and 70.9%) for serology (assuming that both tests were 100% specific). In low-prevalence flocks (estimated prevalence <2%), the flock-sensitivities of pooled faecal culture and serology were 82% (57 and 96%) and 33% (19 and 49%), respectively, compared to 96% (85 and 99.5%) and 85% (72 and 93%), respectively, in higher-prevalence flocks (estimated prevalence > or =2%). A Bayesian approach incorporating prior knowledge on flock-specificity of pooled culture produced similar estimates and probability intervals. These estimates assume conditional independence of the two tests, and therefore might have over-estimated the true flock-sensitivities of the tests if the flock-sensitivities of pooled faecal culture and serology were correlated. The estimated minimum flock-specificity of pooled culture when used for surveillance and assurance testing was 99.1% (96.9 and 99.9%). Surveillance and assurance programs in Australia are designed to provide a flock-sensitivity of 95% for an assumed prevalence of 2%. Pooled faecal culture is performing at close to this level--whereas the flock-sensitivity of serology appears to be lower than expected, particularly in lower prevalence flocks.

Animals↗
PubMed2002

Management factors related to seroprevalences to bovine viral-diarrhoea virus, bovine-leukosis virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum in dairy herds in the Canadian Maritimes.

Bovine viral-diarrhoea (BVD), enzootic bovine leukosis (EBL), Johne's disease (JD), and neosporosis lower on-farm productivity, reduce export competitiveness, and increase consumer concerns regarding safety. Our purpose was to examine the relationship between 27 control practices and the estimated true seroprevalences for these four diseases for 2604 cattle in 90 dairy herds in the Maritimes provinces of Canada. Overall, 37.8, 20.4, 3.4, and 19.2% of all sampled cattle were truly exposed to the agents of BVD, EBL, JD, and neosporosis, respectively. The median within-herd true prevalences were 0, 9.3, 0, and 12.3%, respectively. Factor analysis reduced the 27 control practices to two highly correlated factors. Tobit-regression analyses determined that vaccination practices were associated with reduced prevalence of exposure for Bovine viral-diarrhoea and EBL. Also, farms that tended to purchase their dairy animals were associated with higher seroprevalence for Johnes' disease. Neither of these two factors was associated with the seroprevalence of Neospora caninum infection. The few routine biosecurity measures that were investigated in this study were generally not related to the seroprevalences of these farms.

Animal Husbandry↗
PubMed2002

Direct production losses and treatment costs from bovine viral diarrhoea virus, bovine leukosis virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum.

Our purpose was to determine direct production losses (milk loss, premature voluntary culling and reduced slaughter value, mortaliy loss, and abortion and reproductive loss) and treatmetn costs (veterinary services, medication cost, and extra farm labour cost) due to four infectious diseases in the maritime provinces of Canada: bovine viral diarrhoea (BVD), enzootic bovine leukosis (EBL), Johne's Disease (JD), and neosporosis. We used a partial-budget model, and incorporated risk and sensitivity analyses to identify the effects of uncertainty on costs. Total annual costs for an average, infected, 50 cow herd were: JD$ 2472; BVD$ 2421; neosporosis $ 2304; EBL$ 806. The stochastic nature of the proportion of infected herds and prevalence of infection within a herd were used to estimate probability distributions for these ex post costs. For all diseases, these distributions were right skewed. A sensitivity analysis showed the largest effect on costs was due to milk yield effects. For example, changing milk production loss from 0 to 5% for BVD increased the costs for the disease by 266%.

Abattoirs↗
PubMed2000

Automation of an absorbed enzyme immunoassay for the detection of Mycobacterium paratuberculosis antibodies for an eradication program.

As part of an ongoing Johne's disease eradication program by the state of Victoria, Australia, the Victorian Veterinary Pathology Services (VVPS) has been involved in testing over 150000 cattle samples per year for the presence of Johne's-specific antibodies. The Parachek kit (CSL, Victoria, Australia) has been used throughout the project. This method was automated using a Rosys 3300 and a Plato 7 (Dade/Behring Diagnostics) to pipette samples and the Behring ELISA Processor 3 (Dade/Behring Diagnostics) to wash EIA plates, add reagents, reads absorbances and perform data reduction of the results. Automation saved about 15h of labour per day, allowing one staff member to analyse up to 2000 samples per 8h shift compared to 800 samples using a manual protocol. Problems that were encountered include pipetting issues, the reading of the Paracheck endpoint, and excessive packaging of the kit. Maintenance, calibration and control of the analysers were an integral part of the process. VVPS, working in conjunction with CSL, suggested modification to the Parachek kit to make automation of the product more convenient. The approach resulted in a change in reagent volume and a reduction in packaging that reduced the cost of the test by 25%.

Animals↗