A retrospective analysis of domestic sheep and goat Mycobacterium avium subspecies paratuberculosis diagnostic results from the Washington Animal Disease Diagnostic Laboratory.

Current MAP diagnostic practices in small ruminants poorly align with evidence-based recommendations favoring fecal PCR over serum ELISA.

This retrospective study analyzed Mycobacterium avium subspecies paratuberculosis (MAP, Johne's disease) diagnostic trends in domestic sheep and goats submitted to the Washington Animal Disease Diagnostic Laboratory (WADDL) between May 2015 and June 2024. A total of 108,092 serum ELISA samples and 1,090 fecal PCR samples were evaluated. The study revealed a striking 6-fold difference in positive prevalence between two commercially available ELISA platforms: IDEXX (0.9% submissions, 1.0% individuals, 3.7% herds) versus VMRD (5.8% submissions, 5.8% individuals, 24.2% herds), underscoring significant variability in test characteristics between manufacturers. Fecal PCR demonstrated positive prevalences of 6.5% per submission, 6.6% per individual, and 11.2% per herd. Species-level differences were assessed by ELISA manufacturer, age, sex, and breed. The overwhelming reliance on serum ELISA (98.9% of MAP diagnostic submissions) compared to fecal PCR contrasts sharply with established recommendations, which advocate using ELISA primarily as a herd-level screening tool in high-prevalence herds (≥5% test positive), while reserving fecal PCR or culture for surveillance, eradication efforts, and clinical diagnosis confirmation. These findings highlight a disconnect between current diagnostic practices among producers and veterinarians and evidence-based guidelines for MAP control in small ruminants, with important implications for disease management programs across the United States.

This summary was distilled by AI and may occasionally misinterpret data. Confirm critical details with the primary literature before clinical application.