Anthrax at the Farm Level

Barry Whitworth, DVM

Area Food/Animal Quality and

Health Specialist for Eastern Oklahoma 

Recently, several areas of Oklahoma have experienced record flooding.  On rare occasions in Oklahoma, the disease anthrax has been associated with abnormally wet weather.  According to a report written in the Journal of the America Veterinary Medical Association in 1959, Oklahoma experienced a large outbreak of anthrax in 1957.  Anthrax-related animal deaths occurred in eight Oklahoma counties.  Craig County suffered the most losses.  Ottawa and Mayes Counties had substantial losses as well.  The total number of animals lost in Oklahoma was nearly 1,000 animals.  Most of the animals that died of anthrax were cattle, but a small number of sheep, pigs and horses also died.  Two non-fatal human cases were reported as well.  The epidemic was brought under control by an effective quarantine and vaccination program.

The report emphasized that wet weather and alkaline soils influenced the 1957 outbreak.  Another factor that may have played a part in the outbreak was the cattle trails.  These trails were used in the 1800’s to move cattle north.  All of these factors most likely contributed to outbreak. 

Anthrax is caused by Bacillus anthracis.  The spores of this bacterium are highly resistant.  They can remain in the soil for long periods of time.  Cattle, sheep and goats are most susceptible to the organism.  Other animals such as horses, pigs, dogs and cats have been infected on occasions.  Anthrax is a zoonotic organism.

Animals can be infected with the “vegetative cells” of the bacterium.  Fortunately, the “vegetative cells” are usually destroyed by the acidic environment of the stomach.  Spores of the bacterium are the most common form that infect animals.  The most common way that ruminants acquire anthrax is by ingestion.  Many times, this follows a drought or excessive rain fall event.  In extremely dry years, cattle graze close to the soil and pick up the spores.  During a flooding episode, the flood waters move the spores, and they are deposited on pastures or concentrated in low lying areas where animals graze.  Rarely, animals may be infected with the anthrax by inhaling the spores in dust.  Another way to be infected is by spores contaminating a wound.  It has also been suggested that biting flies can infect animals.

Animals infected with anthrax will show clinical signs of the disease in one to 14 days.  Usually, in ruminants, the signs of the infection occur in three to seven days.  The most common clinical finding is a dead animal.  If a producer finds a sick animal with anthrax, the clinical signs are excitement, fever, anorexia, ruminal stasis, abdominal pain, blood in the urine and blood-tinged diarrhea.  Clinical signs seen just before death are depression, muscle tremors, staggers, labored breathing and convulsions.

Read more in the August 2019 issue of Oklahoma Farm & Ranch.