What is Bovine Johne's disease
Bovine Johne's (pronounced 'yo-nees') disease is a fatal wasting disease of cattle, goats, alpaca and deer caused by a chronic bacterial infection.
What causes Johne's disease?
Johne's disease is caused by the bacterium Mycobacterium paratuberculosis. These bacteria can survive 12 or more months in a favourable environment, such as swampy or wetter areas of a farm.
What are the signs of Johne's disease?
Cattle are usually infected when less than 12 months of age. However, due to a long incubation period, clinical disease is often not seen until the affected animal is at least 4 or 5 years of age. Signs may appear after a period of stress such as calving, poor nutrition, heavy milk production or any other cause.
As the bacteria lodge and multiply in the wall of the small intestine, the cow responds by producing inflammatory cells. This combination of bacteria and cells leads to a thickening and distortion of the gut wall. Eventually the gut fails to absorb water and nutrients. In dairy cattle, the first sign is often a drop in milk production. Affected animals then develop chronic diarrhoea. Cattle gradually lose weight and become emaciated, while still maintaining a good appetite. They may also develop 'bottle jaw', a swelling under the jaw.
How are cattle infected with Johne's disease?
Cattle up to 12 months of age are most susceptible to infection, particularly calves less than 3 months old. Infected cattle shed bacteria in their manure and contaminate the environment before showing signs of Johne's disease. However, the greatest contamination comes from animals showing signs of Johne's disease. Calves become infected as they drink from an udder contaminated with manure, or eat or drink feed or water contaminated by manure.
Calves can also become infected while in the cow's uterus, however this is less common. The likelihood of this is increased if the cow is showing signs of Johne's disease.
Infected cattle may also shed the bacteria in their milk. When calves drink this milk they can become infected.
What is the treatment for Johne's disease?
There is no treatment for Johne's disease. While certain antibiotics may provide some temporary relief, infected cattle will inevitably die.
How is Johne's disease controlled?
There are various approaches to controlling Johne's disease when it occurs in a herd. These will depend on a range of factors. Contact your private veterinarian for further information.
Can cattle be vaccinated against Johne's disease?
A vaccine is available to aid the control of Johne's disease in infected herds. Contact your private veterinarian for further information.
How is Johne's disease prevented?
The main way that infection occurs is by the introduction of an infected animal to a herd. The risk of this occurring can be minimised by seeking a written declaration of the health status of livestock for cattle being introduced. Discuss farm biosecurity further with your private veterinarian.
Further information about Johne's disease can be obtained from your private veterinarian, Agriculture Victoria animal health staff or refer to our Bovine Johnes Disease webpage.