Clostridial diseases are caused by an anaerobic bacillus of the family Clostridia, they are widely distributed in the farm and small holding environment and can be the classic cause of sudden death in sheep.
Healthy sheep have low levels of clostridia in their gut and it is only when a sheep’s natural immunity is compromised that clostridial diseases can become a problem. Unfortunately, these disease outbreaks are unpredictable. Some factors which can lead to a problem include a sudden change in diet, a change such as turnout to lush grazing, or housing, and any stresses, e.g. bullying, or the presence of other diseases.
Table of contents
The six main clostridial diseases in sheep are:
- Lamb dysentery (bloody scours) caused by C. perfringens
- Pulpy kidney or enterotoxemia (overeating disease) caused by C. perfringens
- Black disease caused by C. novyi
- Braxy caused by C. septicum
- Blackleg caused by C. chauvoei
- Tetanus (lock jaw) caused by C. tetani
Lamb Dysentery
There are five types of C. perfringens and all can cause disease in sheep. The different types will vary in which they produce toxins. Types B and D both produce lethal toxins which are responsible for the symptoms seen in lamb dysentery and in pulpy kidney.
Lamb dysentery is usually seen in lambs that are less than 3 weeks old. Unfortunately, the disease can come on quite quickly so the normal first sign is sadly a dead lamb. Some lambs can show clinical signs such as lack of interest in sucking the teat, lethargic and bloody diarrhoea. These lambs normally come from unvaccinated ewes, meaning they have not received sufficient antibodies through the maternal colostrum to be able to fight the infection.
The sheep and lambs potentially eat spores of the bacteria which are able to live in soils for upwards of a year. The bacteria then multiplies in their intestines, which can cause problems.
Pulpy Kidney in Sheep
Pulpy kidney, also known as enterotoxaemia, typically happens when there is a sudden change in the sheep’s diet. This is usually to a feed that is higher in protein, starch, or sugar. Most healthy sheep have a small population of C. perfringens in their intestines. But there aren’t enough bacteria to cause a major problem. The bacteria can have quickly multiplied in response to extra feed, meaning they can then release a huge amount of toxins.
This is what then causes the symptoms and eventual death of the sheep or lamb. Signs of pulpy kidney are lethargy and going off feed, clear indicators of stomach pain and diarrhoea. As the disease progresses, the toxin begins to affect the brain and they can lose the ability to stand and show muscle spasms.
Black Disease and Braxy in Sheep
Black disease, or infectious necrotic hepatitis, is very common in sheep. If the spores are ingested, they can remain inactive in the sheep’s liver for long periods of time. If the liver tissue becomes damaged, usually because of liver fluke, the spores become activated and quickly begin multiplying and produce toxins.
Clinical signs are rarely seen in animals with this disease, and death is usually sudden. Affected animals are often healthy, 2-4 years old, and always infected with liver fluke. As such, a management technique for this disease is to try and control the incidence of liver fluke in a flock, however this is not always possible.
Braxy is quite similar to other clostridial diseases with sudden death as the most likely sign of the disease.
Blackleg and Tetanus in Sheep
Blackleg and tetanus in sheep are both caused by infection of any wounds the sheep may have. These could be caused by shearing cuts, cut by a fence, or castration where an open wound becomes contaminated.
The bacteria in the wound produce toxins that cause a wide range of effects from dying of tissues to paralysis and muscle spasms.
Unlike the other clostridial diseases these diseases tend to show clinical signs before sudden death of the animal. The most common symptoms are stiffness of limbs and difficulty walking, and in tetanus, muscle spasms; while in Blackleg, swelling of the affected area, lameness, and a very high fever. Few lambs or ewes recover from these diseases, and there is currently no effective licensed treatment. Tetanus Antitoxin may be used to prevent onset of tetanus in unvaccinated animals, but only before onset of clinical signs.
How do I know if I have got clostridial disease?
Having a good flock management program can help you track and prevent an outbreak of the disease. It’s a good idea to have a clear idea of the sheep in your flock – you should know where they came from, their backgrounds and their age groups.
Knowing your flocks and farm or small holding history can help as well. If your farm or small holding has had problems in the past with clostridia, then a vaccination program is a good idea.
Sometimes there can be no indication until the symptoms appear.
How do you treat clostridial disease?
Unfortunately, as most infected animals will be found dying or dead, the only antibiotic to kill the bacteria (penicillin) is usually ineffective. Supportive treatment is normally the most common way forward but unfortunately there is no guarantee of a live ewe or lamb.
Therefore, vaccinations are vital to protect your sheep & lambs from these devastating diseases.
Can clostridial diseases be prevented?
The main way to protect against clostridial diseases in sheep is vaccination.
Vaccines
There are vaccines available now for all of the major Clostridia bacteria in sheep. They are highly effective in almost all cases.
Good vaccination greatly reduces the occurrence of diseases in adult sheep. Lambs from vaccinated sheep are also protected.
It is also important to manage the other factors which can lead to sheep having problems
Managing stress factors such as handling, drenching, shearing, and other disease management can all help. It is also important to manage transitioning the sheep from one feed to another, as this can be a major risk factor.
Lambing season can also be a major stress, the best way to prevent an outbreak of any clostridial disease in a flock is vaccination. Many vaccines are broad spectrum and cover a variety of different species of Clostridia.
Colostrum from vaccinated (and boosted!) ewes
A newborn lamb should get immunity through the colostrum milk from their mothers, assuming the mother was correctly vaccinated before lambing. This immunity from the colostrum will cover them for the first 12 to 16 weeks of their lives.
Lambs that have had their mothers die immediately, or soon after birth, must be assumed not to be vaccinated by their owners. In cases like this you should start a full course of the vaccine at 1 to 2 weeks old, with a second dose at 4-6 weeks old.
It is important to select the most appropriate vaccine based on local conditions and the prevalence of disease on your farm or small holding. If a ewe who is breeding has already had vaccines for these diseases, all she will need is a booster vaccine two to eight weeks before lambing. If not, two doses of the relevant vaccine should be given at an appropriate interval with the final dose four to six weeks before lambing.
This will provide protection for the dam during this period of high stress and provide protection for the lamb through the colostrum it receives. It is important to consult your veterinary surgeon or SQP professional for flock-specific information and a more tailored vaccination programme for you and your farm or small holding.
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