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Anthrax: A veterinary public health perspective By This is an acute disease that affects most warm blooded animals including man. It is caused by the bacterium Bacillus anthracis and is characterized by a febrile septicemia which is rapidly fatal. It occurs sporadically in South Dakota, Nebraska, Arkansas, Mississippi, Louisiana, Texas, and California. The occasional epidemics in man are local industrial outbreaks among employees who work with animal products. It is also called malignant pustule, malignant edema, woolsorters disease, ragpicker’s disease and chabron.
Bacillus anthracis is a gram positive, non motile spore forming bacterium about 4.8 x 1-1.5um. They form spores when exposed to oxygen especially after an affected dead animal is opened. They incubate in neutral or alkaline soil with the spores changing to the infective or vegetative forms under optimal environmental conditions which occurs in seasons when the daily temperature is more than 60F, accompanied with heavy rainfall. Animals can also contract the infection by biting insects or eating of contaminated feedstuff. Pigs, dog, cats and minks have been known to contract the disease from eating contaminated meat. Spores may remain infected for years.
In animals, the disease starts after an average of a 3-7 day incubation period. The course ranging from peracute to chronic. The peracute is characterized by sudden onset and is rapidly fatal. The affected animals may stagger, tremble, convulse and collapse. In the acute case, there would be a sudden rise in temperature, followed by a period of excitement then depression and collapse. Pregnant animals may abort and there may be bloody discharges from natural openings in the body. This blood seldom clots.
In man, three forms are recognized, cutaenous, inhalation and gastro intestinal. Cutaenous usually affects the skin and rarely involves the lungs or gastro intestinal tract. It is characterized by itching of the affected skin surface which develops into a depressed black spot often surrounded by secondary vesicles. Pain is unusual. Untreated cases of cutaenous anthrax has a fatality of 5 to 20%, but seldom occurs after antibiotic therapy. Initial signs of inhalation anthrax are mild and non specific sometimes presenting as flu, fever and shock in 3 to 6 days, with death occurring shortly thereafter. Gastrointestinal anthrax is difficult to diagnose and is spread from eating of undercooked infected meals. Natural infection in man is by contact with tissues of animals [cattle, sheep, goats, horses, pigs dying of the disease or contaminated hair, wool, hides and soil associated with infected animals]. When spores are inhaled, inhalation anthrax occurs. Do not attempt to find out how the suspicious powder on your hands smells like! There is no evidence that milk from infected animals transmits anthrax. THERE IS NO EVIDENCE OF MAN TO MAN TRANSMISSION..
When an animal dies from anthrax, rigor mortis is absent or incomplete, the dead animal would be bloated and the body would decompose rapidly. There should be no post mortem done on these animals unless by trained experts. Moving of these carcasses should be avoided as much as possible. The public health department should be contacted immediately. Diagnosis is by sending blood to the laboratory. Other disease conditions that might mimic anthrax are- tetanus, bloat, lightning stroke, sunstroke leptospirosis, lead poisoning and conditions causing pharyngeal swelling.
Anthrax can be treated early if exposure is suspected, with Penicillin. Tetracyclines and other broad spectrum antibiotics are effective. Please do not ask your veterinarian to start your animal off with Ciprox as there would not be any top range antibiotics to use if resistance occurs. Livestock animals could be vaccinated before the season when outbreaks occur. Penicillin is the drug of choice.
To contain this disease and prevent spread, always notify the Veterinary Public Health Department of your city, if your animal dies after exhibiting the above signs. Dispose manure, bedding or other contaminated materials by cremation. If the source of the outbreak is contaminated soil, these areas should be avoided and children playing here are at risk. Foodstuffs to animal might also act as a source and this should not be obtained from the abattoir. Control scavengers that feed on dead animals. Observation of general sanitary procedures by persons are very important. Personal cleanliness and care of skin abrasions are essential. A cell free vaccine is available for use in man. October 2001
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