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disease. ❑ Usually, infection occurs when the animals are very young. ❑ Infection lies latent and may flare up to cause obvious disease later in life. ❑ In cattle and sheep the signs of disease usually develop when the animals are middle-aged and the disease progresses over a period of months or years. ❑ In goats the signs can
Sheep infected with Ovine Johne’ s Disease
appear from about eight months of age and they can develop quickly, causing death within weeks. The cause of OJD is a bacterium, Mycobacterium paratuberculosis. The disease spreads when bacteria are shed in the faeces of infected animals, whether they have diarrhoea or not. The disease can spread from mother to young in the womb, and via her milk or as a result of faecal
contamination of her udder when the baby suckles. An important feature of the disease is that animals are most susceptible to infection when they are young. It is likely that most infections occur in the first few weeks or months of life. The sheep disease of the greatest concern in South Africa at present is ovine Johne ' s disease( OJD), which can come into a flock by purchasing just one " normal " sheep. According to the Ruminant Veterinary Association of South Africa( RuVASA) it is important to avoid the disease on your property if you keep sheep, for the following reasons: ❑ It can be introduced to a flock by buying just one apparently healthy sheep; ❑ Once in a flock OJD is virtually impossible to eradicate;
LIVESTOCK
❑ Being positive means eternal quarantine; ❑ Control rests on neverending vaccination; ❑ Vaccination is very effective in lowering the impact of OJD but does not eliminate it; ❑ Left unmanaged, it can cause annual deaths of 10 % or more of the breeding ewes. Johne ' s disease should not be
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Emaciated cattle
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