There are a number of clostridial diseases that affect cattle and sheep in this country. They are generally characterised by acutely ill animals (sick very suddenly) that are often found dead or die within 24 hours of the initial signs of illness.

The prognosis for almost all clostridial diseases is extremely poor, with mortality approaching 100% in most cases. Therefore, the most important thing with clostridial diseases is prevention.

Blackleg

Blackleg is caused by Clostridium chauvoei, and is more common in cattle than sheep. It primarily affects cattle under two years of age. As with most clostridial diseases, the bacterial spores gain entry to the animal’s body by ingestion. These spores are very resistant and may lie dormant in soil for many years, until brought to the surface by ploughing, reseeding or suitable climatic conditions.

Once cattle eat the spores, they have the ability to traverse the gut wall and settle out in particular parts of the body. In the case of Clostridium chauvoei, the spores have a tropism for muscle, particularly the large muscle masses of the shoulder, rump and hamstring areas.

Disease occurs when the muscle containing the clostridial spores suffers an insult or trauma that creates a suitably anaerobic environment for sporulation and bacterial replication.

As the bacteria grow and multiply, they produce copious amounts of toxins which lead to gangrene of the affected muscle and a severe, fatal septicaemia (blood poison).

Symptoms

Usually, Blackleg is characterised by sudden death. In early cases, animals may display lameness, depression, lack of appetite, reluctance to move and a high temperature (over 40ºC).

The most characteristic clinical sign associated with Blackleg is the feeling of crepitation under the skin overlying the affected muscle. This is due to subcutaneous emphysema (gas bubbles under the skin produced by the bacteria) and feels similar to bubble-wrap. This skin will be insensitive to pain and is often discoloured.

The animal becomes progressively duller, before becoming recumbent, followed by death. If the heart or respiratory muscles are affected, death occurs rapidly and animals are usually found dead.

Diagnosis

Clinical signs are often diagnostic. On post-mortem, dark coloured muscle is seen and organisms can be recovered from tissues and identified.

Treatment

Treatment is rarely successful, even if initiated early. On occasion, the injection of twice daily penicillin, allied to the surgical exposure, removal and flushing of gangrenous muscle, may prevent a fatal septicaemia from occurring, with subsequent sloughing of remaining dead tissue.

Prevention

Prevention of Blackleg involves the use of Blackleg vaccines on an annual basis, especially in young stock. Blackleg vaccines for cattle include Blackleg Vaccine; Tribovax-T; Tribovax-10; Covexin 8 and Covexin 10. These vaccines require a two-injection course separated by an interval of four to six weeks, to be completed two to three weeks prior to the main risk period.

The risk period is late spring and summer in general, so calves should be vaccinated in April. All animals should then receive an annual booster. In herds where Blackleg has been a problem in the past, repeat vaccination at six monthly intervals may be necessary.

In sheep, the following vaccines are available: Covexin 8; Covexin-10; Heptavac; Heptavac P Plus; and Ovivac P Plus.

Black's disease

Black’s Disease is caused by Clostridium novyi Type B and is primarily associated with sudden deaths in both sheep and cattle. In this case, the clostridial spores are awakened in the liver by migrating liver fluke. Once the bacteria germinate, they produce toxins which lead to severe local liver damage, toxaemia (blood poison) and death.

Symptoms

In the early stages of disease, affected animals may have a very high temperature (40ºC to 41ºC) and often show signs of abdominal pain, i.e. grunting or grinding the teeth. Affected sheep/cattle quickly become depressed and progress to toxic shock with sunken eyes, hypothermia and respiratory distress. Death usually occurs within 24 hours.

Diagnosis

Diagnosis is made by finding classical lesions of infarction and necrosis in the liver on post-mortem, together with isolation of the offending organism. There is usually evidence of recent liver fluke migration and toxaemia also.

Treatment

Treatment is futile in almost all cases. If initiated, treatment involves the use of high doses of penicillin, together with anti-inflammatories and intravenous and oral fluids to combat the toxic shock.

Prevention

Prevention also involves vaccination against Clostridium novyi Type B which is included in Tribovax-T; Tribovax- 10; Covexin-8; Covexin 10; Heptavac and Heptavac P Plus. Vaccination should be carried out as for blackleg. The control of liver fluke is also a crucial component in reducing the risk of Black’s Disease in sheep and cattle.

BHU

Bacillary Haemoglobinuria (BHU) is caused by Clostridium haemolyticum, also known as Clostridium novyi Type D, and primarily affects cattle, with occasional disease in sheep. Like Black’s disease, it is an acute, highly fatal, toxaemic infectious disease.

Again, spores which are ingested from soil and finally lie dormant in the liver are most commonly activated by migrating liver fluke. The bacteria which then proliferate produce toxins which lead to damage to red blood cells and are highly fatal. This disease is most common in particular regions, most notably Limerick and Cork.

Symptoms

Affected cattle are acutely sick with high temperatures, abdominal pain and dark coloured (port wine) urine. Death, due to blood poison and blood loss through the urine, usually occurs within 24 hours.

Diagnosis

Diagnosis is often based on past history on the farm together with the finding of port wine-coloured urine. On post-mortem a large liver lesion is seen similar to Black’s Disease and the offending organism can usually be isolated.

Treatment

Treatment is usually fruitless, but involves treatment with high doses of penicillin, anti-inflammatories and blood transfusions.

Prevention

Prevention is similar to Black’s Disease using the vaccines Tribovax-T; Tribovax- 10; Covexin-8; and Covexin 10.

Tetanus

All domestic animals can develop tetanus but cattle are the least susceptible, with horses being the most susceptible. It is caused by the bacteria Clostridium tetani, and commonly occurs following a penetrating injury or a surgical procedure in the three weeks prior to the onset of clinical signs.

The use of ‘banders’ as a means of castration of bulls increases the risk of tetanus, as does open, surgical castration in unvaccinated animals.

Symptoms

The disease occurs following contamination of a wound by spores of Clostridium tetani from soil. If the wound environment is suitable, the spores germinate and bacteria multiply and produce a neurotoxin which affects all parts of the nervous system, i.e. peripheral nerves as well as brain and spinal cord. The early signs of disease include stiffness, muscle tremors and difficulty chewing or swallowing. Cattle often develop bloat and may have a raised tail and pointed ears. Later in the disease, animals become recumbent and die from respiratory failure.

Treatment

Treatment is worthwhile in cattle in the early stages of the disease even though the prognosis is still guarded. Treatment involves the administration of tetanus antitoxin, penicillin and sedatives.

Prevention

Tetanus can be prevented by vaccinating with the following vaccines: Tribovax-T; Tribovax- 10; Covexin-8; Covexin 10; Heptavac and Heptavac P Plus.

Botulism

Botulism is a sporadic disease of cattle and occasionally sheep in Ireland. It is caused by Clostridium botulinum toxin which leads to progressive muscle paralysis throughout the body.

It is classically associated with cattle grazing on pasture close to a poultry plant or chicken factory, or with cattle grazed on pasture on which poultry litter has been spread. It has occasionally been linked to feeding of round baled silage contaminated with toxin from bits of bird or animal carcases that have been picked up by the baler.

Symptoms

In really acute cases, animals may be found dead. In most cases, however, botulism is characterised by a progressive hindlimb weakness, with animals having difficulty rising, and swaying during walking.

Diagnosis

Diagnosis is based on ruling out other potential causes of weakness and paralysis, together with a thorough onfarm investigation to evaluate the diet and assess for risk factors.

Treatment

There is no treatment for botulism apart from removing the animal from the source of toxin.

Prevention

There is no available vaccine for botulism. Cattle should not be grazed on pasture where chicken litter has been spread and proper disposal dead animals is imperative.