Anthrax, a highly infectious and fatal disease of mammals and humans, is caused by a relatively large spore-forming rectangular-shaped bacterium called bacillus anthracis.
Anthrax occurs on all continents, causes acute mortality in ruminants, and is a zoonosis. The bacteria produce extremely potent toxins which are responsible for the ill effects, causing a high mortality rate. While most mammals are susceptible, anthrax is typically a disease of ruminants and humans.
It does not typically spread from animal to animal nor from person to person. The bacteria produces spores in contact with oxygen.
Sudden death (often within 2 or 3 hours despite the animals appearing to be normal) is by far the most common sign.
Very occasionally, they show signs of trembling, a high temperature, difficulty breathing, they may collapse and have convulsions before succumbing to death. This usually occurs within a period of 24 hours;
After death blood may clot, resulting in a small amount of bloody discharge from the nose, mouth, and other openings
Rod-shaped bacteria surrounded by a capsule are visible in blood smears made from surface blood vessels
Post-mortem examinations should not be undertaken on suspected anthrax cases (including any cow that has died suddenly for no apparent reason) until a blood smear has proved negative);
If a carcass is opened accidentally, the spleen is usually swollen and there is bloodstained fluid in all body cavities.
Due to the rapidity of the disease, treatment is seldom possible. However, high doses of penicillin have been shown to be effective in the later stages of some outbreaks.
Infection is usually acquired through the ingestion of contaminated soil, fodder, or compound feed. Anthrax spores in the soil are very resistant and can cause disease when ingested even years after an outbreak. The spores are brought to the surface by wet weather, or by deep tilling, and when ingested or inhaled by ruminants the disease reappears.
Where an outbreak has occurred, carcasses must be disposed of properly, the carcass should not be open (exposure to oxygen will allow the bacteria to form spores) and premises should be quarantined until all susceptible animals are vaccinated.
Vaccination in endemic areas is very important. Although vaccination will prevent outbreaks, veterinary services sometimes fail to vaccinate when the disease has not appeared for several years. Nevertheless, the spores survive for such lengthy periods and the risk is always present.
Anthrax is a disease listed in the World Organization for Animal Health (OIE) Terrestrial Animal Health Code, 2011, (Article 1.2.3) and must be reported to the OIE (Chapter 1.1.2 Notification of Diseases and Epidemiological Information).