Descriptive analysis of the changes in Johne's disease management practices on Ontario dairy farms through repeat risk assessment

Abstract

Johne's disease (JD) control is often based on the culling of positive animals and the adoption of management practices that minimize exposure of calves to the pathogen Mycobacterium avium ssp. paratuberculosis (MAP). From 2010 to 2013, Ontario, Canada, instituted a voluntary Johne's control program consisting of whole-herd testing and a Risk Assessment and Management Plan (RAMP). The RAMP consisted of 38 questions that evaluated 5 different management areas to characterize herd risk for MAP introduction and within-herd spread. The RAMP produced a numerical score for each area, with higher scores associated with higher risk. The RAMP focused on animal purchases, calving management, calf management, and heifer and cow cleanliness and management. In the summer of 2019, the RAMP was repeated on 180 farms that had participated in the JD program of 2010 to 2013 and had bulk tank milk ELISA results from 2013 and 2017. This cross-sectional study demonstrated that many producers changed management practices over the 4-to 7-year period. Producers changed their cattle buying practices, with a reduction in purchasing from multiple sources and more herds refraining from buying in animals. However, overall scores were higher in 2019 than in 2013. The 2019 RAMP indicated that fewer farms were utilizing individual calving pens in 2019 than in 2013 (13% vs. 26%), yet more farms had policies in place to deal with sick or suspect JD cows entering the maternity area (92% vs. 74%). Management changes occurred over time, some of which represent increased risk (crowded maternity pens) and others decreased risk (closed herd, protocols in place for JD-positive cows) for MAP introduction and transmission. These results highlight the importance of frequent risk assessments and the documentation of changes to management practices on-farm as a means to assess herd disease risk more accurately.

Analysis of the Veterinary Risk Assessment and Management Plan questionnaire responses for dairy herds enrolled in the Northern Ireland Johne's disease control programme

“…Purchasing of cattle from infected herds or infected individuals is one of the main risk factors for JD transmission between herds 18 . In Ireland, studies have shown that approximately 60%–80% of dairy herds purchase cattle to bring into the herd, 18,19 comparable to the data (89.4%) from this study, which shows that herds that report no animal introductions are a minority 20 . Due to the lack of JD test information available at time of purchase, farmers are likely to purchase high or unknown JD risk animals and then manage risk of onward JD spread through quarterly milk testing.…”

“… 18 In Ireland, studies have shown that approximately 60%–80% of dairy herds purchase cattle to bring into the herd, 18 , 19 comparable to the data (89.4%) from this study, which shows that herds that report no animal introductions are a minority. 20 Due to the lack of JD test information available at time of purchase, farmers are likely to purchase high or unknown JD risk animals and then manage risk of onward JD spread through quarterly milk testing. Multivariate logistical regression analysis of the VRAMP data found that farmers were significantly more likely to have identified a suspected case of JD within the herd if they had kept one or more purchased animals for breeding.…”