Anthrax is a soil-borne bacterial infection of domestic animals, wild animals, and man Anthrax is caused by the spore-forming organism Bacillus anthracis. It is most common in wild and domestic herbivores - cattle, sheep, goats, camels, antelopes - but it also occurs in humans exposed to tissue from infected animals, contaminated animal products, or directly to anthrax spores. It doesn't affect chickens but it is common in ostriches.

Anthrax occurs all over the world. It is more common in warm climates as spore formation only occurs when the temperature is between 20C and 40C, the humidity is over 60% and the pH is above 6.0. Under such conditions spore formation occurs rapidly, leading to the contamination of soil and water, where the spore may survive for years; up to 30 years in some cases. Spores are formed in the presence of oxygen. Within a carcase the organisms rapidly die. Only when they are exposed to air and oxygen do they form spores.

The disease is transmitted through pastures which are contaminated by the spores. The animals may be forced during drought to graze on short grass which may be contaminated by the infected soil. Anthrax spores can remain infective in soil for many years. During this time they are a potential source of infection to grazing livestock. Grazing animals may become infected when they ingest sufficient numbers of these spores from the soil.

Depending on the route of infection, host factors, and potentially strain specific factors, anthrax can have several different clinical presentations.

The anthrax bacillus produces a lethal toxin in the animals which causes accumulation of fluid (oedema) and tissue damage, resulting in death from shock and kidney failure.

In very severe forms, there is a short illness and this makes the disease difficult to treat. The animal develops high fever, difficult breathing followed by convulsion, collapse and death.

In ruminants such as cattle, sheep and goats, the symptoms of anthrax are very sudden and severe, with death occurring within minutes to hours. There is staggering, high fever, rapid breathing, trembling, collapse, and a few convulsive movements, followed by death. Usually the animal is found dead, with bloody discharges from body openings. Rigor mortis is often absent or incomplete, with marked bloating and rapid decomposition. The blood is dark and thickened and fails to clot readily. If by mistake the carcase is opened it will be noticed that the spleen is greatly enlarged and the pulp soft and tarry.

In severe forms, the disease would last about 2 - 3 days before death. The animal will appear depressed, listless and have high fever. The mucus membranes in the eyes and gums are congested and hemorrhagic. There is difficulty in breathing caused by edematous swelling in the throat.

In less severe cases, some animals may survive for 1 week and others will recover. In dogs, humans, horses and pigs, the disease is usually less severe. Sometimes there may be swelling in the lower neck, chest and shoulders, especially in animals such as pigs, camels and horses.

In both severe and less severe cases, affected cows may abort and have a reduction in milk production. The milk will be blood stained or appear yellowish in color. Infection in the alimentary tract may cause dysentery.

In any case of sudden death anthrax must be suspected and a veterinarian informed so that a diagnosis can be made. Bloat, lightning strike, blackquarter, snakebite, and plant poisoning can also cause sudden death. It is highly risky for unqualified laboratory personnel to take samples of the disease. The sampling procedure should be carried out by qualified laboratory personnel.

The vet will stain a blood smear or smear from a lymph node, abdominal fluid or subcutaneous oedema and examine it under the microscope to give a rapid diagnosis. Only if the result is negative should the post mortem examination proceed. Under the microscope the organism appear as large square ended rods with a pink capsule.

Prevention and control requires a strict adherence to veterinary regulations to prevent and minimize the spread of the disease among livestock and humans.

Note
The carcass of any animal suspected to have died of Anthrax should not be opened but must instead be burnt or buried at a depth of at least 2 meters, and the surrounding area burnt and treated with 10% formalin or 10% caustic soda to prevent contamination of the environment.

Signs after death:

• Carcase is stiff and bloated
• Decomposition is rapid
• Bleeding from ears, mouth, nose, anus or vagina
• Blood is dark and does not clot

Contaminated beddings, premises and feeds should be destroyed or thoroughly disinfected

Vaccination of all livestock at risk should be done annually as a legal requirement. The avirulent live Sterne- strain spore vaccine, which has lost its ability to form capsules, is available in most countries and offers annual protection. In Kenya a commercially available product called "Blanthrax" is used for the annual vaccinations against Blackwater and Anthrax.

Quarantine should be imposed in all infected areas to prevent movement of animals into and out of such areas. Such quarantine should be not lifted until at least 6 months after disinfection procedures are complete.

The appropriate authorities must be notified

General sanitary measures must be observed by all persons handling diseased animals, both for their own safety and to prevent spread of the disease.

Scavengers, including dogs, jackals and birds, must be controlled and kept away from dead animals to minimize spread of infection

Remove healthy animals from the vicinity where an animal has died.

Bacillus anthracis is susceptible to penicillin, streptomycin and tetracyclines and these may be used by a qualified veterinarian either to treat infected animals in the unlikely event that they are seen alive, or to give protection to in-contact animals. This is then followed by vaccination about 7-10 days later.

Infected carcases must be either effectively burnt or buried at depth of at least 2 meters and the surrounding area burnt and treated with 10% formalin or 10% caustic soda.