Description of Disease:
Anthrax is an acute fatal disease of virtually all animals and is caused by the bacterium Bacillus anthracis. It is particularly prevalent in cattle but it also affects horses, goats, sheep and frequently game.  Humans occasionally become infected by coming into contact with wool, skin or meat of infected animals.

When an animal dies, blood exudes from the nose and anus and contaminates the environment.  This material contains masses of bacteria which (after exposure to oxygen) rapidly form spores capable of surviving in the soil for many years. During rainstorms these spores are washed into pans and rivers causing animals to become infected. Sometimes animals are also infected by biting flies.  If anthrax has occurred on a farm, such a property should be considered permanently infected.

The disease has a rapid development and animals seldom appear ill.  They can die within a few hours after the first signs are observed.  As already stated B. anthracis bacteria form resistant spores when they are exposed to air.  Consequently, infected carcasses of animals suspected to have died of anthrax should not be opened. Since anthrax is a notifiable disease, any suspected case should immediately be reported to the local state veterinarian.

Back to list

Description of Disease
Botulism or lamsiekte is primarily a disease of cattle. Under some circumstances horses, sheep, goats, chickens, ostriches and other birds may also be affected. The disease occurs sporadically in sheep in the dry areas of the NorthWestern Cape and Namibia. It is essentially a paralytic condition, which is usually followed by death. 

Botulism is caused by the toxins of bacteria known as Clostridium botulinum types C and D. The bacteria form resistant spores and are widespread in the soil in most parts of the world. They multiply in decomposing protein-rich animal or plant material eg carcasses of rats, tortoises, hares and birds as well as bean and lucerne hay. In these types of material the bacteria produce very potent toxins which are taken in by mouth and absorbed through the intestine. 

In general the symptoms of botulism are as follows: the animals walk unsteadily as if afraid, lie down and stand only with difficulty, and eventually become completely paralyzed. Saliva dribbles from the mouth because the animals are unable to swallow, the tongues become paralyzed, can easily be pulled out and cannot readily be retracted. The tails also become paralyzed and the faeces hard. Animals usually die within a day or two after lying down, but they may survive for up to 10 days. If an animal ingests a large amount of toxin it can die within 12 hours. In other animals the symptoms are essentially the same as in cattle, namely paralysis with abnormal muscle movements. There are no typical postmortem lesions. 

Botulism occurs under the following circumstances:

1. In areas that are subject to prolonged droughts the phosphorus and protein content of the grass during winter is very low and animals grazing on such veld develop severe deficiencies. Phosphate deficiency is characterized by poor growth, general weakness of the bones, a stiff gait and an abnormal appetite known as pica. Pica is worsened by the protein deficiency. Such animals chew old bones and will eat any decomposed carcass material. If such carcasses or bones are contaminated with Clostridium botulinum, the toxin taken in will initiate the disease. 

2. If a small animal, such as a cat or a rat, dies in a drinking trough, in a silo or a place where fodder is stored, the bacteria may multiply in such a carcass and contaminate the surrounding feed. When such contaminated feed is ingested by dairy cows or horses, they will contract botulism. Sometimes a rotting carcass may lie in drinking water and animals which consume this water may also die. Decomposing protein- rich hay, such as bean or lucerne hay, may occasionally produce botulism in cattle and sheep. 

3. Poultry litter that contains decomposing carcasses and which is fed to cattle or sheep may be a major source of botulism, particularly if it becomes wet. 

Back to list

Description of Disease
Tetanus or lockjaw is a disease which affects virtually all animals and man. Horses and humans are the most sensitive victims of the disease while cattle are less susceptible. Young lambs are frequently affected. The disease is caused by the toxin of Clostridium tetani. The bacteria multiply in the dead tissue of a wound. The potent toxin is absorbed from the wound and moves along the nerves to the brain and spinal cord, causing typical nervous symptoms. 

The most common wounds in which the bacteria multiply are caused by castration and docking. The bacteria may also occasionally contaminate and infect the navel. The use of rubber bands for docking is particularly dangerous and must be avoided in unprotected lambs. These bands cause necrosis of the skin which creates ideal conditions for the bacteria to multiply and extensive losses have been incurred with this procedure. Clostridium tetani is extremely common in faeces and in the soil of kraals and stables and readily infects wounds. 

A lamb suffering from tetanus shows typical nervous symptoms. It lies down and has great difficulty in standing. Later the animal may become so stiff that it falls over and cannot rise again. The legs are stiffly extended and the whole body is tense. The neck is drawn backward and the jaw is closed tightly. When such an animal is disturbed it may go into a tetanic spasm. 


Back to list

VACCINES AGAINST VIRAL DISEASES

Name of disease	Horsesickness
Name of vaccine	Onderstepoort Horsesickness Vaccine 1 & 2
	Product Code: 2063

Description of Disease
Horsesickness is an acute insect-transmitted disease caused by an orbivirus. It affects the equine family and can lead to a high mortality especially in horses and mules. 

Horsesickness is transmitted by bloodsucking midges (Culicoides) and therefore usually occurs in late summer and autumn when these midges are abundant. Warm, moist weather conditions promote the hatching of the insects which are active at dusk, particularly in low lying areas such as valleys and around dams and pans. During winter, especially in areas where severe cold and frost occur, the insect vectors disappear and cases of horsesickness therefore do not occur between June and November. 

There are 9 known serotypes of horsesickness virus in nature. These serotypes differ immunologically and there is no cross-protection between them. This means that a horse may contract horsesickness repeatedly and in spite of the use of a polyvalent vaccine effective immunization is not always possible. Some horses do not react to one or more of the serotypes contained in the vaccine which may be the result of interference between the virus types in the vaccine. Some horses show a poor immune response. 

The disease may manifest in 4 different forms, namely: horsesickness fever, "dunkop" horsesickness, "dikkop" horsesickness and a mixed form. Horsesickness fever is a mild form of the disease characterized by a fever that lasts 1 to 6 days. The animals resistance is lowered, making them susceptible to relapses of billiary fever. It could often be misdiagnosed as a relapse of horsesickness during convalescence.

"Dunkop" horsesickness mainly affects the lungs. Clinical signs include a high fever, and accelerated and laboured breathing. The animal stands with legs apart and its head hanging and froth coming from the nostrils. It usually dies as a result of suffocation.

"Dikkop" horsesickness (oedematous or cardiac form) is characterized by subcutaneous swellings, especially above the eyes, eyelids, lips, lower jaw and the lower parts of the neck, chest and stomach. The lower parts of the legs never show any swelling. Death usually ensues as a result of cardiac failure. The mixed form shows clinical signs of both "dunkop" and "dikkop" horsesickness.
Back to list

Name of disease	Equine Influenza  ("horse flu")
Name of vaccine	Onderstepoort Bivalent Equine Influenza Vaccine
	Product code: 2036

Description of Disease
Equine influenza is a highly contagious viral disease caused by the influenza A-Equi-virus. It is classified under the family Orthomyxoviridae. It occurred in South Africa for the first time in December 1986 and spread to all the major centres in the country and can now be regarded as endemic.

The equine influenza virus that occurs in South Africa (Equi 2) affects the respiratory system of susceptible horses, donkeys, mules and zebras of any age. After a short incubation period of 18 to 24 hours a sudden fever, clear watery nasal discharge and red mucous membranes develop. A typical dry cough ("Newmarket cough") develops early in the course of the disease and often horses, but particularly donkeys, may exhibit continuous bouts of coughing. A stiff gait may be seen because of muscle pain.

The course of the disease is approximately 1 week and recovery is usually uneventful provided a rest period of at least 3 weeks is permitted during convalescence. Serious complications and more severe disease will be seen in newborn foals of nonimmune dams, very old animals or horses with respiratory problems. In these cases complications such as fatal pneumonia, damage to the heart muscle, emphysema, sinusitis and gutteral pouch infection may occur. The death rate in donkeys is higher compared to other hosts because of the higher incidence of secondary bacterial infection.

The virus is transmitted through aerosol produced when infected horses cough or sneeze. This produces a very fine spray of virus particles which is readily inhaled by other horses. Transmission of the disease by contact with infected clothing, instruments, etc. is possible but less important than aerosol transmission.
Back to list