Ralph Phillips

UCCE Farm Advisor, Kern County

Range/Natural Resources/Livestock

October 2001

Ranch Biosecurity - Antrax

There is a lot of talk in the news about bioterrorism. There is another threat to the livestock industry from within itself and the way it manages activities on the ranch. Biosecurity is the term currently used which means to be careful when going from one ranch to another, particularly if there is a disease on one of the ranches. Being careful would include cleaning your clothes and footware before entering a new ranch and again when you get home. When it is possible, quarantine new animals coming onto the ranch. It would also be wise to quarantine strays.

Another consideration would be to limit the number of people coming onto the ranch. This is particularly recommended if you do not know the background of these people.

Limiting the number of people is important when animals are in confined areas and particularly important when the cattle are under stress (weaning, etc.). Although this information is not new to most ranchers, it is a good time to review all procedures in managing potential exposure to new diseases.

Anthrax is not a new disease to Kern County. Since anthrax is in the news, I am taking this opportunity to share some of the latest information with you.

The Animal Health Branch - Emergency Disease Programs has historical records dating from 1926 showing 35 anthrax outbreaks in twelve counties of California. During 1984, an anthrax outbreak occurred in the Carrisa Plains that affected 12 general areas, and killed 43 cattle and 135 sheep. Since 1991, there have only been ten known cases of anthrax in California livestock, nine of which occurred in cattle.

With the thoughts of bioterrorism and reported human anthrax cases, this article will review anthrax primarily as it occurs in cattle so that livestock owners may be aware of the signs and risk factors of anthrax in cattle.

The bacteria, Bacillus antracis, causes anthrax. The bacteria are found in two states - the vegetative state and the spore state. The vegetative state is the growing, reproducing form of the bacteria found in infected animals and people. The vegetative form causes the anthrax disease. If untreated, the disease in animals in generally fatal. After an animal dies from anthrax, if a veterinarian opens the carcass during a necropsy, scavengers or by the decay, the vegetative state is exposed to oxygen in the air. When the vegetative state is exposed to oxygen in the air, it forms spores. The spores are highly resistant to disinfectants and remain viable for years in the soil. The spores are found naturally in the soil of California and western states. When the spores enter another animal, usually through grazing contaminated vegetation or inhaling spores, the bacteria revert to the disease causing vegetative form.

In cattle, a common initial sign is animals found suddenly dead. The disease is usually short at 1?3 days. Once an outbreak begins, animals may be seen with fever, lack of rumination, excitement following by depression, difficulty breathing, uncoordinated movements, convulsions and death. Bloody discharges from the natural body openings as well as edema in different parts of the body are sometimes observed. Some animals may be saved if treated very early with penicillin or tetracycline.

In animals that die, bloody discharges from the body openings are commonly found. Enlargement of the spleen is almost always present. An open, decaying carcass as well as discharges and secretions from the carcass or dying animals will contaminate the ground and protected spores will develop. The vegetative form of the bacteria dies rapidly in unopened carcasses.

Most outbreaks occur in areas where animals have previously died of anthrax, as the spores remain viable for many years. Spores over 35 years old have been able to cause the disease. Often, the outbreaks occur after climatic changes such as heavy rain, flooding, or drought. Climatic changes bring spores to the ground surface and perhaps concentrates the spores in low spots. Working the land may also bring the spores up to the soil surface. Once the animals eat the spores, the vegetative develops, multiplies and is ready to cause anthrax again. In August 2000, an anthrax outbreak in Nevada killed 30 cattle. This outbreak was associated with a recent ditch cleaning, which may have disturbed spores deep in the soil.

When anthrax is suspected, dead animals should not be opened for routine examination, as the discharges and blood are highly infectious to humans and other animals. Your veterinarian can confirm anthrax by taking blood from a peripheral vein (ear or tail) and submitting it to the diagnostic laboratory. Proper carcass disposal is important to prevent surface soil contamination. Vaccines are available to protect animals in endemic areas or when outbreaks occur.

Always keep in mind that anthrax can cause serious disease in people as well as animals. Three syndromes are recognized in people: skin, respiratory or inhaled and intestinal. For this reason, great care should be taken to protect anyone handling the carcass or live animals suspected to have anthrax. Meat obtained from animals dying of unknown causes, or suspected of having anthrax or another infectious disease, should not be consumed.

In summary, anthrax is caused by bacteria that can exist in two forms. The vegetative form causes disease in both animals and people, but is rapidly killed in unopened carcasses. The spore form lives for years in the soil. When the spores surface, they revert to the vegetative form to cause further disease when eaten by animals. Carcasses of animals dying from anthrax should not be opened, because the vegetative form turns to spores when exposed to air. Use caution when handling animals or animal carcasses suspected of being infected with anthrax. Suspected cases of anthrax should be reported to your veterinarian first and then to state animal health officials. District animal health officials are available 24 hours a day to assist your veterinarian in managing an outbreak and minimizing losses.

For more information, call one of CDEFA Animal Health Branches:

Headquarters (916) 654-1447
Fresno District (559) 237-1843

Source:
John Kirk, DVM, MPVM, Veterinary Medicine Extension, School of Veterinary Medicine, University of California Davis, Tulare, CA.
Heidi Hamlen, DVM, MS, DACVPM, California Department of Food and Agriculture, Animal Health Branch Disease Program, Sacramento, CA.