CLOSTRIDIAL DISEASE IN SHEEP AND CATTLE

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Everett Arnold
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1 Vet Times The website for the veterinary profession CLOSTRIDIAL DISEASE IN SHEEP AND CATTLE Author : GRAHAM DUNCANSON Categories : Vets Date : August 11, 2008 GRAHAM DUNCANSON discusses how the many types of clostridial disease impact on ruminant welfare and health THE general public is now well aware of clostridial diseases, thanks to cases of Clostridium difficile causing human deaths, particularly in older patients in hospital for other conditions. However, the pathogenesis of clostridial disease is certainly not widely understood, even in the farming community - where these conditions play a very prominent role. It is a mercy that the general public are not aware that C difficile is an emergent disease causing neonatal deaths in pigs and has been associated with diarrhoea in horses. However, both these animals and the zoonotic implications are outside the remit of this article. I shall deal with clostridial diseases in sheep and cattle. I will discuss them in alphabetical order, concentrating on sheep. However, I will add information regarding cattle where it is appropriate. Bacillary haemoglobinuria This disease has been reported in the UK. It can be called redwater. This leads to confusion with babesiosis in cattle, which we do get in Norfolk, and with bracken poisoning in sheep, which is seen in other parts of the UK. It is caused by C haemolytica, and cattle may be found dead or severely ill. The signs include abdominal pain, jaundice, dysentery and, as the name suggests, haemoglobinuria. 1 / 11

2 The latter is the main sign in sheep. Aggressive treatment with penicillin and fluid therapy, particularly with whole blood, may be successful. On postmor postmortem, anaemic liver infarcts are pathognomic for the condition. Blackleg Blackleg is an acute febrile disease normally associated with cattle, rather than sheep. It is caused by C chauvoei and the organism is said to be found in normal animals intestines. However, I think it is more likely that infection comes from the soil, where it can remain without multiplication for many years. Only one farm in my area has had such a problem, which was the site of a tannery more than a century ago. As the name suggests, this condition is associated with acute-onset lameness. This quickly becomes a generalised febrile condition and death is the invariable outcome. I do not recommend the routine vaccination of cattle, except as part of a vaccination package against malignant oedema, which will be discussed later. In my experience, the sheep disease is extremely rare in the UK. This may be because immunisation against the disease is usually included in a multivalent vaccine. The sheep disease is meant to follow shearing wounds and dog bites, but this has not been my experience. I have only seen the disease on the lower slopes of Mount Kenya in hair sheep and goats. I assumed that the organism was common in the soil, as th disease was common in cattle in the same area. Black disease The correct name for this condition is infectious necrotic hepatitis. It is caused by C novyi type B. In my experience, it occurs in the opposite frequency in sheep and cattle to blackleg - I have seen it relatively commonly in sheep in Norfolk, but never in cattle. The trigger factor is acute fluke - the migration of immature flukes through the liver. Acute fluke occurs often in Norfolk s sheep, and I do see acute fluke in cattle. One would think that a vaccination programme would cover sheep. However, agistment sheep often come from northern England and Scotland, where they are said to be covered but, I believe, have only received one dose of vaccine. These animals meet a heavy infection of flukes and they die from acute fluke or from the resulting necrotic hepatitis from black disease. Botulism Unlike the previous two conditions, the organism C botulinum multiplies in the soil in silage and not 2 / 11

3 in the sheep or cow. The organism produces toxins outside the body. Therefore, the severity of the disease will be affected by the amount of toxin ingested. In my experience, either the sheep is more resistant to the toxin or the animal does not eat silage contaminated with soil. I have never seen the condition in sheep, but it does occur (although rarely in Norfolk-based cattle). I have seen a flock of sheep affected with botulism in Western Australia; the afflicted animals had a mortality rate of more than 50 per cent. The animals had been in drought conditions and there was no association with silage feeding. In Norfolk, the morbidity in a cattle outbreak is very low, with just one or two animals found with a flaccid paralysis. The pathognomic sign is a flaccid anus when you take the rectal temperature. There is no specific treatment, but the animals will recover if they can be kept alive with oral fluids. Braxy Braxy is a disease that only occurs in sheep and is caused by C septicum. I think it is a British disease, as I have discussed it with European colleagues and they are unfamiliar with the condition. Friends from Australian, New Zealand and South African are also ignorant of the problem. The trigger factor is thought to be eating frosted root crops. In Norfolk, these are frosted sugar beet tops. The resulting abomasitis is thought to allow entry of C septicum. I do struggle with this pathogenesis, as I find it hard to understand how the frosted roots bypass the rumen. I wonder if a low level of helminth migration is not the causative factor. C septicum is included in several polyvaliant vaccines. Enterotoxaemia Enterotoxaemia is more commonly called pulpy kidney and is caused by C perfringens type D. It is a sheep disease (as opposed to a cattle disease, but it is a very common disease in goats). In my experience, it is the most common clostridial disease. It is found in growing lambs in inadequately vaccinated commercial flocks. The toxoid is included in every vaccine, so there is little excuse for vaccination failure. However, the main reasons this occurs include: The sheep keeper erroneously assumes that lambs from vaccinated mothers will be covered until they reach slaughter weight. This is not the case, and lambs from vaccinated mothers should have their first dose of vaccine by 10 weeks of age, followed by a second dose four to six weeks later. Lambs from unvaccinated mothers should be vaccinated as early as four weeks of age, with a second dose four to six weeks later. Where the risk was very high in the Kent orchards, we used to give a dose of vaccine within the first two days of life. 3 / 11

4 Lambs are often sold at weaning and given the first dose of vaccine. They are said to be vaccinated, which is not the case - a second dose is required. If the administration of the second dose is unduly delayed, the whole vaccination process should be started again. Although I keep telling hobby farmers about the merits of vaccination, there is a complete mental block with some owners regarding the subject. From a welfare stance, this ignorance is not acceptable. Enterotoxaemia can actually occur in sheep of any age that are unvaccinated. I associate it with growing sheep, but the disease can occur at any time in pet sheep. The disease is normally manifested by sudden death, although observant keepers will see sick, cold and moribund animals beforehand. There is no treatment, and diagnosis will not pose a problem on postmortem examination. The abdomen, pleural cavity and pericardium will be filled with fluid that is usually bloody. The kidneys will be friable, as the common name suggests. There is a high level of sugar in the urine, which can be tested by a small animal dipstick. Lamb dysentery I have not seen this condition since I left Kent in It is caused by C perfringens type B and is a disease found in young lambs. They often die before they develop dysentery, and the only method of control is to have lambs born from fully vaccinated ewes. The ewes need to have received a booster injection four to six weeks prior to lambing. Obviously, the lamb needs to have received adequate colostrum in the first 12 hours of life to achieve passive immunity. I do not know the reason why the disease seems to have disappeared - perhaps one of our readers knows the answer? I cannot believe it is because of vaccination; if that were the case, I would have expected a drop in the number of cases of enterotoxaemia - and that has certainly not occurred. Malignant oedema Malignant oedema, which is found in cattle as well as sheep, is caused by C sordelli. Animals can be found dead or in extremis and show swellings, which are often gaseous. The disease may follow wounds obtained by rams fighting. It is often then called big head disease. In cattle, the organism may gain entrance at parturition and cause massive swelling of the hindquarters. Practitioners have a dilemma: the disease is not common, but a good vaccine is now available that is not overly expensive. How much should we be pushing our farmers, particularly those with cattle (who are not used to routinely vaccinating cattle against clostridial diseases), to vaccinate? Struck I was born in Kent and brought up on a sheep farm, so I am very familiar with this disease. It is 4 / 11

5 common in Kent but very rare elsewhere. I have only seen one outbreak in Norfolk in more than 30 years. It is caused by C perfringens type C and, as the name suggests, it causes sudden death. There is no standard trigger factor, but I think very heavily fertilised grass under fruit trees is likely to be the culprit. Tetanus I am sure the causative organism C tetani is well known to readers, as is its pathogenesis. In my experience it is rare in sheep, owing to vaccination. However, it can still occur in individual cattle. I experienced an outbreak in three Ayrshire cows 22 years ago, which were all down calvers. The first to become affected was 10 days after a Caesarean section. The other two were normal calving cows, but located in the same loose yard. They survived with aggressive penicillin treatment and fluids by mouth. The yard was cleaned out and, the next year, every cow was vaccinated. The disease never returned and the cows are not vaccinated now. Conclusion Raders will have become aware of a theme running through this article - that sheep and cattle require not only the clostridial organism, but also a trigger factor. Prevention of all clostridial diseases, except for botulism, can be accomplished by a very inexpensive vaccination. They are very painful diseases, normally resulting in death. I consider it a welfare consideration if animals at risk, particularly sheep, are not immunised. I think it is up to us, as practitioners, to urge our commercial and hobby farmers to carry out regular vaccination. 5 / 11

6 Malignant oedema might follow an open castration. 6 / 11

7 Rams due for a vasectomy should always be covered for tetanus. 7 / 11

8 Rams that have head wounds may get big head disease. 8 / 11

9 Left: a Buhner suture might potentiate a clostridial infection. 9 / 11

10 Right: damage at calving may allow Clostridium sordelli to invade. 10 / 11

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TOC INDEX. Clostridial Diseases. Lyle Petrie. Take Home Message. Introduction

TOC INDEX. Clostridial Diseases. Lyle Petrie. Take Home Message. Introduction TOC INDEX Clostridial Diseases Lyle Petrie Take Home Message The diseases caused by the clostridial group of organisms, such as blackleg caused by Clostridium chauvoei in young, well-fed beef cattle, are