Johne's Disease

Johne's Disease is a bacterial, clinical disease that has been reported from 20% of dairy herds over a three-year period probably with up to 60% of animals infected
Estimated annual cost of Johne's Disease to the New Zealand agricultural sector is more than NZ$40M
Johne's Disease is revealed as chronic wasting in older cows
Effects increase with age, including diarrhoea, reduced milk yield and wasting (usually from around 4 years of age)
Animals are infected for life: there is no known cure
Control includes good hygiene especially for young calves, removing infected animals and maintaining a closed herd.

What is Johne's Disease?

A chronic, contagious and sometimes fatal infection caused by Mycobacterium avium subspecies paratuberculosis (MAP). It is an immune reaction that develops in response to the MAP infection.

The bacteria affect the small intestine in ruminant animals (cattle, deer, sheep, goats and wildlife) and cost New Zealand up $40-$88 million in lost production each year.

What are the signs?

Here lies the problem - while most animals are infected shortly after birth, the signs are not immediate.

Most new infections occur in the first 6 months of life and calves are particularly at risk in their first 30 days. Infected animals excrete the bacteria (Mycobacterium avium paratuberculosis) in faeces in increasing amounts over years as the infection develops. Even then, the disease usually remains sub-clinical in dairy cows with only occasional animals showing the classical wasting, persistent scouring and loss of body condition. Only in these older and clinically affected animals are the bacteria likely to be found in milk or colostrum.

At the advanced stage, signs of Johne's Disease include wasting and chronic diarrhoea, leading to emaciation. In the early stages, it can only be identified through a blood test or testing faeces.

More on the prevention of Johne's Disease.

How is it spread?

Johne's disease is commonly spread from dam to calf, usually through faeces.

Because it is in the environment, spread through infected pastures and waterways, the disease is very contagious. It can only be limited by good hygiene practices - separating calves from dams after initial feeding of colostrum and minimising contact between young and old animals.

How common is it?

Research indicates that up to 20 percent of New Zealand dairy farms have Johne's disease, however only 2-3 percent of farms aware they have it.

There is no country without Johne's. Like the Johne's Disease Research Consortium research underway in New Zealand, research programmes are also underway in Canada, Denmark, Australia, the United States and Ireland.