Infection with small ruminant lentiviruses (SRLV) causes a variety of chronic inflammatory conditions that limit production. Mycobacterium avium subsp. paratuberculosis (MAP) is also a major production-limiting disease of sheep and goats, which causes severe inflammation of the small intestine. Previous studies have indicated that both SRLV and MAP are widespread in small ruminants in Ontario. This study estimated the prevalence of SRLV and MAP co-infection. Serum samples that were previously tested for MAP infection were re-tested for SRLV. The apparent prevalence of co-infection was low, with 3.4% [95% confidence interval (CI): 1.9 to 5.9] and 14.3% (95% CI: 11.6 to 17.5) of sheep and goats respectively, positive for both infections. However, co-infection is widespread with 36.8% (95% CI: 19.1 to 59.1) and 71.4% (95% CI: 52.8 to 84.9) of sheep and goat farms with 1 or more co-infected animals. A significant association was found between SRLV seropositivity and MAP fecal culture (P = 0.021), suggesting that co-infected goats may be more likely to shed MAP in their feces.

The main objective of this study was to identify the circulating strains of Mycobacterium avium subspecies paratuberculosis (Map) in fecal isolates obtained from dairy goat (N = 29 farms) and dairy sheep (N = 21 farms) populations in Ontario, Canada. Further subtyping was performed to determine if there was adequate diversity between strains that could be used to establish Map transmission patterns. Type C was the dominant strain of Map isolates (95.2%) identified in dairy goats (n = 21). Sub-typing of the Type C strains, based on variable number tandem repeats (VNTR) and mycobacterial interspersed repetitive units, identified 3 VNTR types: INMV 1 (n = 10), INMV 2 (n = 10), and a type not previously identified (n = 1). Only 2 sheep isolates could be identified; both were Type S, sub-type III. Current typing methods demonstrate little Map diversity in the dairy goat population and are therefore of limited use to investigate infection patterns.