Guidance on control of Johne's disease in dairy herds
Johne's disease or paratuberculosis is widespread in the major dairying areas of the world. It is a difficult disease to control. The disease can have a significant financial impact on herds through loss of output and early culling, and the welfare of affected animals is compromised.
Strategy for Control of Map in Cows Milk
Johne's disease is an infectious wasting condition of cattle and other ruminants caused by Mycobacterium avium subspecies paratuberculosis, commonly known as Map.
The disease progressively damages the intestines of affected animals, and in cattle this results in profuse and persistent diarrhoea, severe weight loss, loss of condition and infertility. Affected animals eventually and inevitably die. In dairy herds, the presence of Johne's disease will significantly reduce milk yields well before other signs of the disease can be found. Johne's disease is not a notifiable disease in Great Britain (England, Scotland and Wales), but it is notifiable in Northern Ireland.
Diseased animals in general pass large numbers of Map in their faeces. A single diseased animal can therefore pose a high risk to susceptible animals, in particular young calves in the herd. Diseased animals may also excrete Map in milk and colostrum. While cattle remain susceptible to infection throughout life, they are at their most vulnerable in the first few months of life. Calves may be infected in the womb but are more commonly infected through:
The organism is extremely tough and may survive for up to a year on pasture, in slurry and in water.
Map is also a slow growing organism. After infection, it may be years before the infected animal becomes ill. In the early stages of infection, the only way to confirm whether an animal has Johne's disease is to carry out blood tests. These do not detect all infected animals, but at this stage are more likely to identify infection than tests for the organism itself. Signs of the disease are rarely seen before two to three years of age.
When a case of Johne's disease is discovered in a dairy herd, many other animals within the herd will have been exposed to infection. It is very likely that the disease will be developing in several other animals.
If uncontrolled, Johne's disease will have a financial impact on your dairy business. Particular impacts include:
The last part of the article will also provide information on how to protect a young herd from Johne's disease.
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Article made possible through the contribution of Defra.
