Prevalence of Mycobacterium avium subsp paratuberculosis (MAP) ELISA-positive cows and assessment of MAP transmission risk on organic dairy farms in Ontario, Canada

Abstract

Johne's disease (JD) is caused by Mycobacterium avium spp paratuberculosis (MAP). It is an incurable, chronic inflammation of the gastrointestinal tract of cattle that causes diarrhea, weight loss, and reduced production. Commonly recognized risk factors for MAP transmission include purchase of subclinically infected cows and the infection of calves through ingestion of manure, colostrum or milk containing MAP shed by infected cattle. To limit the negative effects of JD on the dairy industry in Ontario, Canada, the voluntary Ontario Johne's Education and Management Assistance Program (OJEMAP) was implemented in January 2010. Producers can participate in MAP antibody ELISA testing and an on-farm risk assessment and management plan (RAMP) with their herd veterinarian. High RAMP scores are associated with high risk for MAP transmission.

Organic farming is one of the fastest growing agricultural sectors worldwide. In Ontario, approximately 80 dairy farms (2% of all dairy farms) are certified organic. While most organic farmers tend to maintain closed herds, which would reduce the risk for JD introduction, they also often support prolonged contact between newborn calves and their dams. These and other factors could potentially influence the risk of MAP transmission as well as JD prevalence and prevention efforts on organic dairy farms. The aim of this cross-sectional study was to assess the Johne's ELISA prevalence and Johne's disease transmission risk on organic dairy farms in Ontario.