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• Infected bulls will have small luid like pustules present on the surface of the penis and sheath.
Once introduced it is diicult and expensive to eradicate IBR. Animals tend to become unapparent carriers.
Systematic testing and elimination of positives has been successful in some countries. Diferent types
of inactivated vaccines are available. Oicially free countries restrict the use of these vaccines.
4.5.4. Clostridial Diseases
Clostridial organisms of various types are found in the soil where they can survive for a long time. Most clostridial
organisms can also occur quite naturally in the gut of healthy animals. They live there causing no trouble,
pass out in the manure of animals, and consequently contaminate the soil. When conditions are favourable
for the uncontrolled growth of clostridial organisms they produce powerful toxins that are usually fatal. Not
all species of clostridia cause disease, but those that do are usually fatal. The major clostridial diseases in cattle
are Blackleg, Tetanus and Botulism. Blackleg
Blackleg is a preventable infectious bacterial disease that usually afects younger animals between 6 to 24
months of age. It is a fatal disease that produces an acute local infection that leads to blood poisoning and
rapid death. Marked lameness and pronounced swelling over the shoulders and thighs caused by the formation
of gas in the subcutaneous tissues are the primary symptoms of Blackleg.
When pressure is applied to the swelling a peculiar crackling sound can be heard. Infected animals have
foul smelling yellowish white faeces and the hindquarters are dirty. Calves become dull and weak, lose weight,
the eyes appear sunken, breathing is rapid, and body temperature drops below normal.
The disease is almost always fatal within 12 to 36 hours. Post- mortem inspection of diseased muscles typically shows
dark tissue with a dry or bubbly appearance Fig. 4.33.
Blackleg is a preventable disease by speciic vaccination and is the most practical method of combating this
disease. Vaccination is normally carried out at weaning.
Figure 4.33. Blackleg post-mortem examination reveals extensive necrosis of the leg musculature with a blackish-red discoloration with a “bubbly” appearance. Source: infograph.venngage.comp91280black-leg.
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Tetanus Tetanus is a preventable disease caused by toxins
produced from the Clostridium tetani bacteria. The bacterial spores are commonly found in soil and animal
faeces. They persist for many years and are resistant to environmental efects.
The usual method of entry of the bacteria is through deep puncture wounds on the body or feet, or as a
result of entry through exposed surgical wounds such as castration. Bacterial spores can remain inactive for
some time and when conditions are right they multiply rapidly in the body, producing toxins that afect the
nervous system of the animal. The incubation period can be from 5 days - 3 weeks.
The disease can last for up to 10 days and is nearly always fatal. Animals are characterised by increased muscle
stifness and muscle tremors, with the head, neck and tail held stily, and restricted jaw movement - referred
to as ‘lockjaw’ Fig. 4.34. The animal eventually cannot stand and may fall over showing muscle spasms with
outstretched limbs. Raised temperatures up to 42
o
C are common, and death is due to muscular spasms coupled
with paralysis of the respiratory muscles.
Figure 4.34. A calf with tetanus following castration. Note the neck and head are extended. Source: National Animal Disease Information Service, United Kingdom.
Tetanus is a preventable disease with speciic vaccination. Calves should be vaccinated twice at an early age
according to manufacturer’s recommendations to generate immunity, and animals retained for breeding
should be vaccinated again on an annual basis. For breeding cows, vaccination should take place at
least six weeks before calving to ensure post-calving immunity is passed to the calf for the period until the
vaccine is administered to the calf to confer long term immunity. Good hygiene practices such as the prompt
treatment of all surgical wounds is also a preventative against tetanus infection.
Botulism Botulism is a preventable disease that is caused by the
ingestion of toxins poisons, which are produced by Clostridium botulinum bacteria commonly found in
soil or on dead and decaying carcasses, decaying plant matter, or feedstufs contaminated with dead animals.
There are several distinct types or strains of botulism commonly referred to as types A, B, C, D and E.
The condition is often associated with cattle experiencing a phosphorus andor protein deiciency. To try and
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overcome this deiciency they begin to chew bones of dead animals where the toxins of the bacteria are found.
In other cases animals grazing on the edges of water courses where decaying plant matter is found can also
pick up toxins. These toxins have a major efect on the nervous system of cattle.
Often the irst sign is the discovery of dead animals. Any sick animals may show signs of unsteady gait, with
a progressive paralysis starting in the back legs and advancing to the front legs through to the jaw and throat.
In advanced cases where the animals generally do not recover, you will see the animal lying down in an upright
position with the head turned back and tucked into their lank Figure 4.35 or head and neck outstretched on the
ground. Generally if you pull the tongue out the animal cannot retract the tongue as the muscles of the throat
are paralysed. Sometimes the animal may be found on its side moving their legs in a slow paddling motion
unable to get up.
Botulism is a preventable disease with speciic vaccination. All calves should be vaccinated with the bi-
Figure 4.35. An advanced case of botulism with the head turned back and tucked into their lank. Source: afrivet.co.za.
valent Botulism Vaccine. This covers the most common types; A and D. Some companies make a one shot
vaccine that provides up to three years protection. If an unvaccinated animal is infected there are no
speciic treatments to remedy the infection. Destroy dead animalscarcasses by either burning or deep burial
to ensure other animals cannot gain access to them.
4.5.5. Other Important Diseases
