Ovine Johne’s disease, or OJD, is also called Paratuberculosis. As this last name indicates, it is related to tuberculosis and is a definite concern for all sheep farmers.
It can get onto a farm mainly when a farmer buys sheep that are infected, but show no signs of ill health. These sheep are called carriers of the disease and will slowly infect others over a period of years.
Many of these sheep may also become carriers without any signs, but eventually some sheep become ill and start to die. They gradually lose weight until they die. There may also be episodes of diarrhoea, where the dung becomes fluid and the hindquarters become soiled with faeces.
Unfortunately, all of these signs can have many other causes and the farmer may treat the sheep for all sorts of things before a correct diagnosis is made. By this time he may be losing 10% of his flock every year due to OJD.
WHAT TO DO
If farmers see these signs or suspect OJD, they should call a veterinarian or an animal health technician to investigate, since they will know the right specimens to take as well as the actions to take if it is OJD. There is a vaccine, but it’s expensive and may only be used if the veterinarian has given permission after it’s been confirmed that OJD is present on the farm.
The best course of action is to try to stay free of OJD. This means that farmers should never buy live sheep (especially rams) from unknown sources. Insist that the seller sign a declaration that his flock is free of OJD (tested) and that he has a closed flock (he doesn’t buy in sheep from outside sources). Otherwise there is a higher risk that the disease can come onto the farm.
- This article was first published in Farming SA.