Johnes's Disease

Johne’s Disease (Mycobacterium avium subsp. paratuberculosis – MAP)

Johne’s disease is a chronic, progressive enteritis caused by Mycobacterium avium subspecies paratuberculosis (MAP), affecting cattle, sheep, goats, and other ruminants. It leads to gradual wasting, reduced productivity, and significant economic loss in both dairy and beef herds.

Transmission occurs primarily via:

• Fecal–oral route, especially through contaminated colostrum or milk
• In utero infection in advanced cases
• Environmental persistence and poor hygiene

Clinical signs in cattle include:

• Chronic weight loss despite good appetite
• Intermittent to persistent watery diarrhea
• Drop in milk production
• In small ruminants: weight loss without diarrhea is more typical

qPCR testing offers:

• Highly sensitive and specific detection of MAP DNA from fecal samples
• Suitable for individual animal testing or herd-level surveillance
• Useful for early detection before overt clinical signs or heavy shedding occurs

Compared to culture (which may take 6–12 weeks), qPCR delivers same-day or next-day results, allowing:

• Rapid culling decisions and disease management
• Targeted testing of high-risk animals (e.g., offspring of positive dams)
• Support for certification programs and closed herd biosecurity

Early identification is essential to control spread, particularly in dairy operations, where colostrum and pooled milk practices may amplify risk.