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- Clostridium chauvoei has always been considered the culprit behind blackleg, and most cattle producers did vaccinate their animals against this disease.
- Any farm can fall victim to blackleg and the group of other Clostridium bacteria that cause gasgangrene and sudden mortalities among cattle. Because infection can cause sudden death, it is usually not possible to successfully treat affected cattle.
- The other Clostridium bacteria are C. novyi type A, C. speticum, C. sordellii and C. perfringens type A which normally plays the biggest role in redgut, a clostridia-related intestinal disease.
- It is crucial for cattle producers to develop a basic knowledge of transmission, disease development and immunity in order to understand why annual vaccination is so important.
- The vaccine available for clostridial diseases contains the inactivated organisms and toxins produced by the organisms. It is mainly antibody-dependent immunity that is generated against the organisms, and specifically against the toxins they produce.
Blackleg remains one of the deadliest livestock diseases and must be prevented at all costs. Dr Danie Odendaal, veterinary consultant and director of Veterinarian Network, says there are several key points of importance when combatting this disease.
Any farm can fall victim to blackleg and the group of other Clostridium bacteria that cause gasgangrene and sudden mortalities among cattle. Because infection can cause sudden death, it is usually not possible to successfully treat affected cattle. Vaccination and good management practices therefore form the basis of prevention – this is also what an annual vaccination plan against these destructive bacterial diseases should be based on.
Causes of blackleg
Clostridium chauvoei has always been considered the culprit behind blackleg, and most cattle producers did vaccinate their animals against this disease. However, it was revealed that, after cases of sudden mortalities in vaccinated herds and using further diagnostics, several other types of Clostridium bacteria can cause the disease, as well as a number of others that can play an exacerbating role or cause the disease on their own.
The other Clostridium bacteria are C. novyi type A, C. speticum, C. sordellii and C. perfringens type A which normally plays the biggest role in redgut, a clostridia-related intestinal disease.
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Transfer and development
Dr Odendaal says it is crucial for cattle producers to develop a basic knowledge of transmission, disease development and immunity in order to understand why annual vaccination is so important.
“The animal ingests the Clostridium organisms responsible for blackleg along with their feed. These organisms enter small wounds in the mucous membrane and are then absorbed into the blood and spread to muscle tissue. In the muscle, the organisms lie dormant without causing disease. The oral mucous membrane is suspected to be one of the most important access routes for the organisms when young animals shed their teeth.”
Clostridium bacteria are anaerobic and can only proliferate in the absence of oxygen. “Hence, dormant Clostridium bacteria do not develop further; this only happens under favourable conditions, like when muscle tissue is badly bruised and prevents the circulation of oxygen-rich blood. This is a common occurrence during the handling of animals, especially when they are in a head clamp. It is therefore understandable that proper handling facilities play a role in disease prevention.
“Clostridium organisms are activated in low-oxygen conditions and rapidly start to multiply and produce toxins. It is these toxins that lead to the death of your animals. Muscle necrosis occurs, and the toxins are absorbed into the bloodstream and distributed to vital organs such as the heart, liver, kidneys and brain (Figure 1).”
Figure 1: Formation and spread of toxins via the blood to vital organs. (Source: Dr Danie Odendaal)
Preventive action
The vaccine available for clostridial diseases contains the inactivated organisms and toxins produced by the organisms. It is mainly antibody-dependent immunity that is generated against the organisms, and specifically against the toxins they produce.
“Because the vaccine is inactivated, animals vaccinated for the first time must receive a booster four to six weeks later. After that, animals must be vaccinated annually to keep antibody levels as high as possible.”
Swollen head
“C. novyi type A causes swollen head, a disease that is more prevalent these days and is sometimes confused with common blackleg.”
Most of the imported broad-spectrum Clostridium vaccines do not contain C. novyi type A, but they do contain C. novyi type B (necrotic liver disease) and/or C. novyi type D (C. haemolyticum), which have not yet been identified as a problem in South Africa.
Read more about the Clostridium bacteria here.
Join forces with your veterinarian
Drafting your annual vaccination plan in collaboration with a herd veterinarian makes for good herd health planning. Fatal bacterial diseases, which include blackleg, swollen head, botulism, other clostridial diseases, Pasteurella, pneumonia and anthrax, are the basis of the annual vaccination plan and must be included as standard.
“Given today’s well-developed vaccine technology, a single broad-spectrum vaccine can provide protection against all these diseases.” – Christal-Lize Muller, Stockfarm
For more information, contact your herd veterinarian or Dr Danie Odendaal at vnet1@absamail.co.za.
