Johne’s disease poses a particular challenge in cattle and deer due to the way it spreads, the lack of treatment, and restrictions around vaccination.

It causes chronic diarrhoea, progressive weight loss, and eventually death. The signs can be subtle at first and are often mistaken for other conditions, but once clinical disease appears, the outcome is inevitable.

Why Is It a Problem in Cattle and Deer?

• No vaccine is approved for use in cattle or deer because it interferes with the tuberculosis (Tb) skin test

• Infected animals may test false-positive to the Tb test, complicating disease management

• Once signs appear, treatment is ineffective

There are ongoing discussions about allowing vaccination for specific cattle classes in low-risk Tb areas, but as of now, vaccination remains off the table.

How Common Is It?

• A 2006 study showed over 50% of deer farms in New Zealand had infected animals, although not all showed signs of disease

• In dairy cattle, infection is widespread. Over half of NZ dairy herds are likely to carry Johne’s

• It is less common in beef herds but still present

Signs to Watch For

• Runny diarrhoea that does not respond to treatment

• Progressive weight loss despite good nutrition

• Eventual emaciation and death or euthanasia

Who Is Most at Risk?

• Cattle: Most commonly seen in dairy cows from three years of age onward, though only one or two may show signs at any time

• Deer: Yearling outbreaks are possible, and individual adult cases can occur from two years of age

Confirming the Diagnosis

These signs can mimic other issues, such as internal parasites or nutritional deficiencies. Always consult a veterinarian. Diagnosis requires:

• Blood testing

• Faecal culture or PCR

• Post-mortem examination in some cases

Control and Prevention

If Johne’s is present on your property:

• Cull clinically affected animals

• Test stock and remove any test-positive ruminants

• Work with your vet to create a long-term plan for control

If your property is disease-free:

• Buy only from herds or flocks with no known Johne’s cases

• Introduce only animals that test negative

• Isolate and monitor new arrivals

How Long Can the Bacteria Survive?

The bacterium Mycobacterium paratuberculosis doesn’t multiply outside the host, but it can persist in the environment:

• Up to 6 months on pasture

• Over 12 months in sheltered, moist areas

Related Articles in This Series

Johne’s Disease: Overview and General Background
Understand the basics of this chronic wasting disease, how it spreads, and its impact across species.

Johne’s Disease in Sheep and Goats
Find out how the disease presents in small ruminants, and why early vaccination matters.