Sheep special: 'Perfect storm' of conditions can trigger cases of pulpy kidney
As lambing draws to a close, the focus is on minimising lamb losses – and clostridial diseases, pulpy kidney in particular, can pose a real threat to a farmer’s bottom line.
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Hannah Noble
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Clostridial diseases pose a serious threat to populations of unvaccinated sheep and come in a variety of different forms including lamb dysentery, braxy, pulpy kidney and blackleg.
Also known as enterotoxaemia, pulpy kidney is caused by the clostridial bacteria Clostridium perfringens. Sheep veterinary consultant, Fiona Lovatt, director of Flock Health, says: “Clostridial diseases are an important threat to farmers. Spores reside in the soil as well as the gut and the fact there is soil on every farm means there is always potentially a risk and no-one can say it does not affect them.”
The bacteria which causes pulpy kidney is naturally occurring in small numbers in the intestine of healthy animals.
The disease develops following the rapid multiplication of the bacteria in the intestines. These bacteria produce a toxin which causes damage to blood vessels, particularly brain capillaries – and affects other organs including the kidneys, as the name suggests, where the body begins to self-digest kidney tissue rapidly.
The most common result of pulpy kidney is sudden death, though lambs may suffer nervous convulsions before they die.
However, deaths are sporadic, they do not necessarily occur in high numbers and they create a very irregular pattern, making predictions difficult.
Dr Lovatt says: “You do not get any warning, lambs which look perfectly fine one day are dead the next and the death is very sudden because it is caused by a toxin in the blood. However, not every sudden death is due to pulpy kidney, it could be pasteurellosis, for example, so make sure you get a post mortem.
“There is no treatment. It has usually killed them before you have time to treat,” she adds.
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Dr Lovatt says: “Lambs on their mothers are at risk as well as older lambs and it is, frustratingly, the best-growing lambs which seem to succumb.”
Pulpy kidney is associated with a dietary change, either transition on to lush pastures or increased concentrate feeding.
Furthermore, if there has been a dry period followed by rain, causing a flush of grass, or farmers have tried to mitigate the effects of the poor weather by creep feeding, the increase of fermentable carbohydrate in the gut can create perfect conditions for the multiplication of the C. perfringens bacteria.
These factors, combined with stress, can create an environment for clostridial bacteria to thrive.
“There is not one trigger for pulpy kidney, all these small factors contribute towards creating issues. The disease is very sporadic, we do not know when it is going to hit,” says Dr Lovatt.
Beneficial
With clostridial diseases and pasteurella, prevention is better than the cure and, as vaccinations for clostridial diseases are among the most effective vaccines for sheep, it is beneficial to invest in vaccination both financially and on welfare grounds.
“Vaccination works as an insurance policy, we do not know when pulpy kidney will hit and some years farmers will get away with it but, when all factors combine to create the problem, you really want to have the safety margin of having a vaccinated flock,” says Dr Lovatt.
Vaccination of ewes should be carried out well before the start of lambing to ensure the ewe has accumulated sufficient immunoglobulins to pass on through colostrum.
Dr Lovatt says if ewes have been properly vaccinated and lambs are leaving the farm quickly, before maternal immunity has decreased, vaccination of lambs is not always necessary. However if pasteurella is a major risk, if lambs are to remain on-farm for longer, or if the ewe flock is unvaccinated, it may be worth considering the lamb’s first vaccination at three weeks old.
She adds: “Remember vaccines only work after two doses, just giving a single dose is a total waste of time.”
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