Associations between lipoarabinomannan enzyme-immuno-assay test results for paratuberculosis and farm-management factors

Abstract

Data from an epidemiological study of paratuberculosis in dairy cattle in Ontario, Canada, were used to identify farm-management factors that were associated with lipoarabinomannan antigen enzyme-immuno-assay (LAM-ELISA) test results for paratuberculosis. The study was conducted in two phases. Phase 1 herd selection was cross-sectional and involved 304 herds. Herd average LAM-ELISA optical density was regressed on management-practice data using least-squares regression, and was associated negatively with teat dipping and the number of years the herd had been established. Phase 2 herd selection was carried out in a case-control manner and involved 120 of the herds that had participated in Phase 1. The 60 highest-risk and 60 lowest-risk herds for paratuberculosis, as defined by Phase 1 LAM-ELISA test results, were visited for sample and data collection during Phase 2. In general, there were no striking differences in management practices observed in a simple comparison of high- to low-risk herds. When herd status was regressed (using logistic regression) on management practices, herd status was associated with calf housing, calf feeding, use of teat dip, adult nutrition, water sources and contact between animals. However, the direction and detail of some of the observed associations were opposite to those that were expected. The results of this analytic observational study were inconclusive. Nevertheless, they provide material to help guide future investigations.