First Case of Anthrax in 2003


Anthrax naturally occurs in Texas and other Great Plains states, and horses occasionally get the disease. The anthrax agent is a resilient spore-forming bacterium called Bacillus anthracis, which lives in the ground. Livestock ingest B. anthracis when they forage close to the ground during drought, or when they eat feed grown on infected soil. Horses seem to be more resistant to anthrax than other livestock species, such as sheep or cattle. Naturally occurring anthrax appears in Texas from late June through October, and outbreaks end with the start of cooler weather.

Hillman explained that rains spawned by Hurricane Claudette soaked counties around Del Rio, and the moisture was followed by a hot, dry spell. "This weather pattern can trigger the germination of dormant anthrax spores in the ground, causing them to migrate to the surface and contaminate soil and grass," he noted.

According to Ralph C. Knowles, DVM, a distinguished life member of the American Association of Equine Practitioners, "Anthrax in the horse is characterized by a high fever (up to 107°F) and a quick death. Rigor mortis is absent or incomplete in an anthrax carcass. Horses frequently have ventral edema (swelling on the belly), are fevered, and are obviously 'sick.' Horse carcasses often have dark blood oozing from the mouth, nostrils, and anus. Diagnosis can be based on these clinical signs, but laboratory confirmation is based on finding B. anthracis in a blood sample or blood culture."

Carla Everett, TAHC information officer, said that most owners vaccinate their horses in areas of disease detection. The anthrax livestock vaccine can be purchased through private veterinarians, feed stores, or animal health product distributors, and it can be administered by veterinarians or livestock producers. The attenuated live vaccine is given once a year, typically in the spring, and it is recommended for livestock residing in or near an outbreak and for animals that will be moved to the area.

"Don't administer the vaccine concurrently with antibiotics," said Everett, and she reminded that vaccinated animals should not be sent to slaughter for at least two months. Consult with your veterinarian for vaccine recommendations, quarantine requirements, and information on disposal of infected animals.

About the Author

Stephanie L. Church, Editor-in-Chief



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