Estimated reading time: 4 minutes
- Clostridial diseases, caused by Clostridium spp. bacteria, are among the leading causes of sudden, unexpected deaths in sheep, often with few visible signs.
- Clostridial diseases are generally classified into three groups, based on disease signs and progression.
- Although Clostridium bacteria are widespread, they multiply rapidly under favourable conditions like when animals have a high nutritional intake or following deworming.
- While clostridial diseases cannot be completely eradicated or avoided, a tailored management programme can significantly reduce risk over time.
- Collaborate with your veterinarian to develop a customised management programme that includes targeted vaccination and sound management strategies.
Clostridial diseases, caused by Clostridium spp. bacteria, are among the leading causes of sudden, unexpected deaths in sheep, often with few visible signs. According to Dr Roland Larson, a veterinarian from Graaff-Reinet, these bacteria are ubiquitous in nature and can even persist in soil due to their ability to thrive in anaerobic (oxygen-poor) environments. They also inhabit the intestinal tract of healthy animals, making them extremely difficult to eliminate or avoid.
Clostridial diseases are generally classified into three groups, based on disease signs and progression: the enterotoxic group primarily inhabits the gastrointestinal tract and produces toxins; the neurotoxic group impacts the nervous system as a result of the toxins the bacteria produce; and the gangrenous groupcauses severe tissue and muscle damage.
Dr Hanré Ferreira, veterinarian and technical support manager at Virbac, explains that although Clostridium bacteria are widespread, they multiply rapidly under favourable conditions like when animals have a high nutritional intake or following deworming. Once they begin to proliferate, they release toxins that damage various body systems, leading to clinical signs and, often, death.
Most prevalent diseases
Clostridium spp. includes several bacterial species that cause a wide range of diseases in sheep:
- Enterotoxic group: The most prevalent clostridial disease in this group is pulpy kidney, followed by blood- and redgut.
- Neurotoxic group: The predominant diseases are tetanus and botulism.
- Gangrenous group: Common diseases are blackleg, swollen head in rams, and uterine gangrene.
However, typical disease signs do not always clearly indicate a specific clostridial infection, and acute deaths often occur when toxins are present. “It often happens that signs are insignificant, as in the case of botulism. Only a post-mortem examination by a veterinarian can confirm the diagnosis,” explains Dr Larson.
As the bacteria multiply and release toxins, these toxins accumulate in the animal’s system. Once levels become excessive death can occur rapidly, and treatment is usually ineffective since the toxins are already circulating.
Some signs that should raise immediate concern include:
- Blackleg: Spongy skin lesions, fever, reduced appetite and rumen activity, stiffness, and lameness.
- Swollen head: Obvious swelling of the head, lethargy, suppressed appetite, lying down, and shallow breathing.
- Botulism: Paralysis of the tongue leading to an inability to feed or drink, progressing to complete paralysis and, in some cases, aggression.
- Tetanus: Stiffness of the legs followed by convulsions, initially triggered by sound or touch.
- Pulpy kidney, blood-, and redgut: These diseases show no warning signs to alert the producer and may also be caused by viral infections or plant poisoning.
Treatment and prevention
Dr Ferreira says that when it comes to clostridial diseases, prevention is far more effective than treatment. “Once toxin levels are high, even potent antibiotics cannot reverse the damage. The bacteria may be eliminated, but the toxins will continue to circulate. If fatalities have already occurred and a diagnosis is confirmed, remaining animals can be treated with penicillin or another suitable antibiotic to inhibit further bacterial growth. However, it may be too late as the success of treatment depends on how much toxin has already been released.”
Dr Larson concurs, noting that delayed intervention often yields limited results. “Management practices play a crucial role, especially when feeding easily digestible sugars. Using chicken litter as feed can also lead to complications such as botulism. Stressed animals are vulnerable to immunosuppression, increasing their susceptibility to various infections. In rare cases, antibiotics may still offer some benefit.”
Dr Ferreira recommends a comprehensive vaccination strategy to prevent these diseases. “The most effective safeguard is a proven vaccine that covers all clostridial strains present on your farm. Work with your veterinarian to select an appropriate multiclostridial vaccine. Sheep should receive a booster three to four weeks after the initial dose to ensure complete protection. Annual revaccination is essential. Keep in mind that healthy animals ingesting adequate trace minerals respond best to vaccines.”
While clostridial diseases cannot be completely eradicated or avoided, a tailored management programme can significantly reduce risk over time. Dr Larson stresses that there is no universal solution: “Each producer’s flock composition, grazing management, feeding strategy, and production goals are unique. Collaborate with your veterinarian to develop a customised management programme that includes targeted vaccination and sound management strategies to prevent disease.” – Koos du Pisanie, Plaas Media
For more information, contact Dr Roland Larson at 082 558 9782 or Dr Hanré Ferreira at 083 695 6246.
