Seroprevalences of antibodies against bovine leukemia virus, bovine viral diarrhea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum in beef and dairy cattle in Manitoba

Of 1204 dairy cows and 1425 beef cows sampled, 60.8% and 10.3% were seropositive for Bovine leukemia virus, 4.5% and 1.7% were seropositive for Mycobacterium avium subspecies paratuberculosis, and 8.3% and 9.1% were seropositive for Neospora caninum, respectively, while 28.1% of dairy herds had unvaccinated animals with titres > or = 1:64 for Bovine viral diarrhea virus.     

Seroprevalence of infection with Mycobacterium avium subspecies paratuberculosis, bovine leukemia virus, and bovine viral diarrhea virus in maritime Canada dairy cattle

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.     

Effects of seropositivity for bovine leukemia virus, bovine viral diarrhoea virus, Mycobacterium avium subspecies paratuberculosis, and Neospora caninum on culling in dairy cattle in four Canadian provinces

The purpose of this research was to determine the effects of seropositivity for exposure to bovine leukemia virus (BLV), bovine viral diarrhoea virus (BVDV), Mycobacterium avium subspecies paratuberculosis (MAP) and Neospora caninum (NC) on overall and reason-specific culling in Canadian dairy cattle. Serum samples from, approximately, 30 randomly selected cows from 134 herds were tested for antibodies against BLV, MAP and NC using commercially available ELISA test kits, while 5 unvaccinated cattle over 6 months of age were tested for antibodies to bovine viral diarrhoea virus (BVDV). For analyzing the time (in days) to culling of cows after the blood testing, a two-step approach was utilized, non-parametric (Kaplan-Meier survival graphs) visualization and then semi-parametric survival modelling (Cox proportional hazards model), while controlling for confounding variables and adjusting for within herd clustering. For all reasons of culling, MAP-seropositive cows had a 1.38 (1.05-1.81, 95% C.I.) times increased hazard of culling compared to MAP-seronegative cows. Seropositivity for the other pathogens was not associated with an increased risk of overall culling. Among cows that were culled because of either decreased reproductive efficiency or decreased milk production or mastitis, MAP-seropositive cows were associated with 1.55 (1.12-2.15, 95% C.I.) times increased hazard compared to MAP-seronegative cows. Among cows that were culled because of reproductive inefficiency, NC-seropositive cows had a 1.43 (1.15-1.79, 95% C.I.) times greater hazard than NC-seronegative cows. Among cows that were culled because of decreased milk production, cows in BVDV-seropositive herds had a 1.86 (1.28-2.70, 95% C.I.) times increased hazard compared to cows in BVDV-seronegative herds. BLV-seropositive cows did not have an increased risk of reason-specific culling as compared to BLV-seronegative cows. No significant interaction on culling among seropositivity for the pathogens was detected, but only a limited number of cows tested seropositive for multiple pathogens. Results from our research will help in better understanding the economic impacts of these pathogens and justification for their control.     

Seroprevalence of Mycobacterium avium subspecies paratuberculosis, Neospora caninum, Bovine leukemia virus, and Bovine viral diarrhea virus infection among dairy cattle and herds in Alberta and agroecological risk factors associated with seropositivity

A province-wide, cross-sectional seroprevalence and agroecological risk factor study of Mycobacterium avium subspecies paratuberculosis (MAP), Neospora caninum (NC), Bovine leukemia virus (BLV), and Bovine viral diarrhea virus (BVDv) genotypes 1 and 2 (BVDv1 and BVDv2) infection in dairy cattle herds in Alberta was conducted. Among adults, the seroprevalence of MAP, NC, and BLV was 9.1%, 18.5%, and 26.9%, respectively. For MAP, based on a herd test cutpoint of 2 or more seropositive cows, 58.8% of herds were infected. Herd-level seroprevalence for NC and BLV was 98.7% and 86.7%, respectively, based on a herd-test cutpoint of 1 seropositive cow. Among unvaccinated dairy heifers, the seroprevalence for BVDv1 and BVDv2 infection was 28.4% and 8.9%, respectively, while herd-level infection was 53.4% and 19.7%. Seroprevalence for MAP varied moderately by agroecological region, whereas that for NC, BLV, and BVDv1 and BVDv2 did not. For MAP, aridity and soil pH (correlated features of the region) were also important.     

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%.     

Bayesian kriging of seroprevalence to Mycobacterium avium subspecies paratuberculosis and Neospora caninum in Alberta beef and dairy cattle

Identifying spatial patterns of risk is important in the study of diseases with ecologic causes. Furthermore, relatively complex hierarchical modeling is required to determine how factors that are organized across levels interact, such as how an ecologic cause interacts with farm management and with animal characteristics. The objective of this study was to map the risk for Mycobacterium avium subspecies paratuberculosis (MAP - the causative agent of Johne's disease) and Neospora caninum (NC - the cause of neosporosis) infections in Alberta beef and dairy cattle. This objective utilized Bayesian generalized linear kriging to partition herd effects into a portion attributable to location and a portion that was independent of location. Seropositivity to NC in beef cattle showed strong support for spatial covariance, suggesting that ecologic causes were important for beef cattle but not dairy cattle. There was little evidence of spatial covariance for MAP seropositivity in either beef or dairy cattle.     

Factors affecting the herd level of antibodies against Mycobacterium avium subspecies paratuberculosis in dairy cattle

A case-control study was made of Norwegian dairy herds with high and low herd levels of antibodies against Mycobacterium avium subspecies paratuberculosis. A high proportion of the herds had a considerable number of seropositive cows, and environmental and management factors were examined for possible associations with the high serological levels of antibodies. The most important appeared to be: geographical location, red deer (Cervus elaphus) gaining access to the pastures for cattle, the observation of wild birds in the feed storage, and herds sharing common pasture with other herds of cattle. However, diagnostic tests showed that none of the animals in the case herds was infected with M a paratuberculosis.     

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.     

Detection of Mycobacterium avium subspecies paratuberculosis in Swiss dairy cattle by culture and serology

Faecal samples from 186 dairy cows representing ten commercial dairy herds with sporadic clinical paratuberculosis (group A), and from 100 dairy cows from herds without a history of paratuberculosis (group B) were cultured for Mycobacterium avium subspecies paratuberculosis (MAP). Two different decontamination methods, a NaOH/oxalic acid method and treatment with 0.75% hexadecylpyridinium chloride (HPC) were performed prior to inoculation of Loewenstein-Jensen agar slants with and without mycobactin. Cultures were incubated for 16 weeks. Acid-fast staining bacteria were identified as MAP on the basis of mycobactin dependency and by PCR-RFLP analysis of the IS 1311-insertion element of M. avium. MAP was grown from 15 out of 186 group A animals (8.1%) whereas faecal culture for MAP was consistently negative in group B. The growth rate of MAP was significantly higher (8.1% vs. 1.6%) and the contamination rate of cultures was significantly lower (17.6% vs. 21.5%) in faecal samples decontaminated with NaOH/oxalic acid than with HPC-treated faecal samples (p<0.01, McNemar's test). Atypical mycobacteria which were grown from 46.8% of NaOH/oxalic acid treated specimens were not obtained from any of the HPC-treated samples. A commercial ELISA with MAP-lipoarabinomannan as the antigen was used to detect MAP-antibodies in unabsorbed sera from all animals. The percentage of ELISA-positive cows was 16.8%. Overall agreement between antibody detection and MAP-positive faecal culture was 15.4%.     

Seroprevalence of Neospora caninum in dairy cattle in Bahia, Brazil.

Sera collected from 447 dairy cattle on 14 dairy farms were tested for Neospora caninum antibodies by use of an immunofluorescent antibody technique. Positive reactions with titres > or =1:200 were found in 63 (14.09%) of animals. Neospora positive sera were also tested for Toxoplasma gondii antibodies by using a commercial latex agglutination test. Antibodies to T. gondii were detected in 3 (4.76%) of 63 N. caninum positive sera. These results indicate that N. caninum infection is widespread among dairy cattle in Bahia state.     

First report of bovine viral diarrhea virus and Mycobacterium avium subspecies paratuberculosis infection in Tibetan sheep (Ovis aries) in Tibetan Plateau,China

Tropical Animal Health and Production - Bovine viral diarrhea virus (BVDV) and Mycobacterium avium subspecies paratuberculosis (MAP) are important pathogens, which cause serious disease in animals....     

Seroprevalence of Neospora caninum infection in dairy and beef cattle in Paraguay

Seroprevalence of Neospora caninum in 879 beef and dairy cattle in different locations of Paraguay was determined by an ELISA. In the survey, 262 (29.8%) cattle were positive to N. caninum, and animals with anti-Neospora antibody titre were observed in all the locations tested in the country. Serum samples taken from a herd that exhibited persistent abortion had the highest percentage of animals being positive to the parasite (17/30, 56.7%). In the same herd, abortion was significantly more likely in animals with high anti-Neospora antibody titre. Immunoblot analysis demonstrated that the banding pattern from positive Paraguayan cattle was similar to that seen with the positive control sample. In conclusion, N. caninum infection is present among Paraguayan beef and dairy cattle, and it may be an important cause of bovine abortion in Paraguay.     

Seroprevalence of and agroecological risk factors for Mycobacterium avium subspecies paratuberculosis and neospora caninum infection among adult beef cattle in cow-calf herds in Alberta, Canada

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.     

Infection by Neospora caninum associated with bovine herpesvirus 1 and bovine viral diarrhea virus in cattle from Minas Gerais State, Brazil

Neospora caninum is a canine parasite which is considered a significant cause of bovine abortion. Two cattle herd groups were serologically studied with the objective of studying the prevalence of infection by N. caninum associated with BHV1 and BVDV infections. In group I, 15 dairy herds (476 samples) naturally infected by the three infectious agents were analyzed,. In group II, three dairy herds (100 samples) of cows vaccinated for two viruses were analyzed, in order to determine the infection prevalence by N. caninum. In the first group, an infection prevalence of 12.61, 34 and 28.3% was determined for N. caninum BHV1 and BVDV, respectively. In the second group, a seropositive prevalence of 46, 85 and 76%, respectively, was determined for N. caninum, BVH1 and BVDV. In the first group, the virus and N. caninum had shown in the first group 4.41% positive samples in association with BVH1, 3.15% with BVDV, and 8.41% with BVH1 and BVDV.     

Seroprevalence of Neospora caninum in aborting dairy cattle in the Czech Republic

A serological survey for antibodies against Neospora caninum in aborting cattle was carried out in the Czech Republic. Serum samples from 463 aborting dairy cows originated from 137 farms from different parts of the Czech Republic were tested for presence of N. caninum antibodies by use of an enzyme-linked immunosorbent assay (ELISA) and an indirect fluorescent antibody test (IFAT). Antibodies (> or = 1:640) to N. caninum were found in 18 (3.9%) of 463 aborting cows. Farm prevalence in aborting cows was 12.4% (17/137). The antibody titres of cows were 1:200 (9 cows), 1:640 (7 cows), 1:1280 (3 cows), 1:2560 (3 cows), 1:5120 (3 cows), 1:10,240 (2 cows) and 1:20,480 (0 cow). A case-control study was conducted to estimate the association of N. caninum infection and abortion. For this 407 serum samples were collected from cows on five dairy farms with repeated occurrence of endemic and sporadic abortion of unidentified etiology. These samples were obtained from aborting cattle (n=44) and normally calving cattle (control group; n=363) and tested for N. caninum antibodies by an immunofluorescent antibody test (IFAT). Overall, 3.19% (13/407) of cows sampled had positive N. caninum fluorescence with a cut-off titre of 1:200. The prevalence of N. caninum was significantly higher (P<0.05) in the aborting group (13.64%; 95% confidence interval (CI): 5.2, 27.4) than in the control group (1.93%; 95% CI: 0.8, 3.9). A strong association between seropositivity and abortion was found, with seropositive cows being eight times more likely to abort than seronegative cows (odds ratio=8; 95% CI: 2.6, 25.1). This first report on the serological prevalence of N. caninum in cows in the Czech Republic verified a strong association between N. caninum infection and abortions in five dairy farms. Thus, the neosporosis should be considered in differential diagnosis of bovine abortion.     

Monensin use against Neospora caninum challenge in dairy cattle

Using a randomized controlled trial design, a randomly allocated intervention group of 15 cows received a slow-release bolus that delivered 100 days of monensin. The negative control group of 15 cows received a placebo bolus that was identical to the monensin bolus, except without the monensin. Two weeks after bolus administration, all cows were challenged with a 2 ml subcutaneous injection of a live tachyzoite suspension. Whole blood and serum samples were collected from each cow every week for the first month post-challenge, and then every 2 weeks for the next 2 months. The extracted DNA from whole blood was tested for the Nc-5 gene fragment of Neospora caninum using a quantitative real time polymerase chain reaction. Serum was tested for antibodies to N. caninum using the IDEXX ELISA. Cows treated with monensin boluses had a significantly lower humoral immune response than cows treated with placebo boluses at one time point post-challenge (week 4 post-challenge). However, when adjusting for repeated measures within cows, the P value for this humoral difference was 0.098. No DNA for N. caninum was detected in either group, likely due to study design features.     

Within-herd contact structure and transmission of Mycobacterium avium subspecies paratuberculosis in a persistently infected dairy cattle herd

Within-herd transmission of pathogens occurs either by direct or by indirect contact between susceptible and infected animals. In dairy herds that are structured into groups, the way in which animals encounter each other and share an environment can affect pathogen transmission. Dairy cattle are heterogeneous in terms of susceptibility and infectivity with respect to Mycobacterium avium subspecies paratuberculosis (Map) transmission. It is mainly young animals that are susceptible and adults that are infectious. Both vertical and horizontal transmission through the ingestion of Map shed into the environment by adults and transiently infected calves can occur. Our objective was to assess the effect of contact structure on Map transmission in persistently infected dairy herds and to examine the effect of isolating calves from other calves or from adults before weaning. We developed a stochastic compartmental model of Map transmission in a closed dairy herd. The model reflects the Map infection process and herd management characteristics. Indirect transmission via the environment was modelled explicitly. Six infection states (susceptible, resistant, transiently infectious, latently infected, subclinically infected, and clinically affected) and two contaminated farm area environments (whole farm and calf area) were modelled. Calves were housed in hutches, individual indoor pens, or group indoor pens. Two different levels of exposure of calves to a farm environment contaminated by adults were possible: no exposure and indirect exposure through fomites. Three herd sizes were studied. We found that contacts between calves before weaning did not influence Map transmission in a herd, whereas the level of exposure of calves to an environment contaminated by adults and the starting age of exposure of calves to adults were pivotal. Early culling of clinically affected adults led to a lower prevalence of infectious adults over time. The results were independent of herd size. Despite the many transmission routes that are known, the best control approach is to limit the exposure of calves to adult faeces through the systematic separation of adults and calves in combination with hygiene measures. Reducing contact between calves does not appear effective.     

The prevalence of milk and serum antibodies to Mycobacterium avium subspecies paratuberculosis in dairy herds in Ontario

This study randomly surveyed 50 dairy herds in Ontario; 18% and 30% of herds had 2 or more milk or serum enzyme-linked immunosorbent assay (ELISA)-positive cows, respectively. The apparent cow level prevalence was 1.7% and 2.6% on the milk and serum ELISA, respectively. The serum and milk assays agreed moderately.