Study assesses tissue ISH test for Johne’s disease in goats

A new study in the Journal of Veterinary Diagnostic Investigation evaluated an RNAscope-based chromogenic in situ hybridization, or ISH, assay for diagnosing paratuberculosis in goats from formalin-fixed, paraffin-embedded intestinal tissue. The Cornell-led team reviewed 20 archived goat cases and 5 negative controls, including 11 multibacillary and 9 paucibacillary infections. The assay showed hybridization signal in 19 of 20 cases overall, including 8 of 9 paucibacillary cases, while all negative controls were negative. The paper was first published online May 14, 2026, and positions ISH as a useful adjunct when standard culture is slow or fresh tissue isn't available. (journals.sagepub.com)

Why it matters: For veterinary diagnosticians and clinicians, Johne’s disease in goats can be difficult to confirm, especially in animals with low bacillary burden or when only fixed tissue is available after necropsy. Current guidance still points to culture and PCR as core tools, but culture can take weeks, and Ziehl-Neelsen staining may miss organisms in some lesions. This study suggests ISH could help reduce diagnostic uncertainty in caprine cases, particularly paucibacillary presentations and autolyzed submissions, although severe autolysis still appeared to limit performance. (aphis.usda.gov)

What to watch: Watch for follow-up validation in larger case sets, and for whether veterinary diagnostic labs begin adding ISH as a routine option for caprine Johne’s workups. (acvp.org)