Anthrax is a serious infectious disease that is caused by Bacillus anthracis (a spore-forming bacteria), which occurs naturally in soil. Although outbreaks are less common in the U.S. than in other countries, sporadic outbreaks do occur, especially in cattle and deer. Sporadic outbreaks are possible because spores allow the bacterium that causes anthrax to survive in the soil for years to decades.
The American Veterinary Medical Association states that in the U.S., natural occurrences are extremely rare, although outbreaks have been reported in California, Louisiana, Mississippi, Nebraska, North Dakota, Oklahoma, South Dakota and Texas. Cases in Montana and Wyoming have also been reported.
Cause of outbreaks
Domestic and wild animals can become infected when they breathe in or ingest spores in contaminated soil, plants or water. Anthrax outbreaks usually occur after periods of drought followed by heavy rains.
Animals are at higher risk of contracting anthrax when they are around disturbed soils, as this increases the chance the bacteria will become airborne. Livestock and wild animals may become infected by ingesting spores while grazing in areas of high soil contamination or through the bites of certain flies. The route of infection in animals is most often ingestion rather than inhalation or inoculation via skin lesions.
Prevention and treatment
The most effective control strategy for animals in widespread areas where the bacteria may be present is vaccination, according to the 2022 Merck Veterinary Manual. In areas where anthrax has occurred in the past, it is recommended to work with your veterinarian to create a yearly vaccination protocol to minimize the risk of an outbreak. A proper vaccination program reduces animal mortality and minimizes the spread of an anthrax outbreak.
If an outbreak occurs, working with your veterinarian promptly is critical because the course of the disease is very rapid. Prompt administration of appropriate antibiotics is essential.
The Merck Veterinary Manual states that animals at risk should be immediately treated with a long-acting antimicrobial to stop all potential incubating infections, followed by vaccination approximately seven to 10 days after treatment. Any animals that become sick after initial treatment or vaccination should be re-treated immediately and revaccinated a month later.
The American Veterinary Medical Association recommends that livestock such as cattle, sheep, goats and horses that are affected by natural anthrax be treated with antibiotics such as penicillin and oxytetracycline. Consider consulting your veterinarian on what they recommend as well.
Additional management practices to prevent and treat anthrax in livestock include quarantine of the affected herd, removal of the herd from the contaminated pasture (if possible), disposal of contaminated carcasses (preferably by burning) and decontamination of contaminated materials.
Symptoms in livestock and wildlife include:
• Sudden death.
• Staggering.
• Difficulty breathing.
• Trembling.
• Uncontrollable movements.
• Fever.
• Bloody diarrhea.
• Colic (in horses).
It is important to work with your veterinarian for a proper diagnosis, as the symptoms listed above are symptoms for other diseases as well.
To prevent and treat an outbreak, it is important to work closely and promptly with your veterinarian to create a vaccination protocol for areas at higher risk of an outbreak (e.g., areas with a prior outbreak), properly diagnose the disease and implement the proper treatment using antibiotics such as penicillin and oxytetracycline.
Make sure to decontaminate all contaminated feed and materials. Properly disposing of carcasses, moving animals out of the contaminated pasture and quarantining sick animals are good management practices to help reduce mortality from anthrax. — University of Wyoming Extension
