Anthrax
What is it?
Anthrax is a disease primarily of plant eating animals, including cattle, horses, mules, sheep, goats, deer, and elk. It is a naturally occurring disease in animals around the world. Anthrax was brought to North America by European settlers bringing animal hides, wool, and other goods that carried anthrax spores. Cattle drives in the 19th and early 20th centuries spread the bacteria in Canada and the U.S.
The disease is caused by a spore-forming bacterium called Bacillus anthracis. Ruminants are the most likely to contract it from ingesting spores while grazing on pasture. The spores become active in the animal’s body and the bacteria multiply, which causes illness.
People can get the disease through contact with infected animals or animal products.
Outbreaks of anthrax in Minnesota usually occur in mid- to late- summer among livestock grazing on pasture. The last outbreak of anthrax was in livestock in northwest Minnesota in 2023.
Transmission
Due to the longevity of the Bacillus anthracis spores in certain soils, it can survive many years before animals are exposed to it. Hay or other dried feedstuffs containing spores have also been identified as a possible route of infection.
Once an animal is infected, it can spread to other animals through blood contact between animals and insects.
Signs and Symptoms
In ruminants, many animals are found dead before any indications of the disease. A significant indicator of anthrax is unclotted blood present at orifices. Additionally, the carcass may not stiffen. Acute cases in ruminants may show signs of high fever, muscle tremors, difficulty breathing, and unclotted blood from wounds.
Diagnosis
Animals on pasture that die suddenly or are found dead should be examined by a veterinarian to determine if anthrax is a potential cause of death. Blood or tissue samples can be collected from the carcass and submitted to a laboratory to test for anthrax. It is important not to open the carcass for a field necropsy when anthrax is suspected to prevent human exposure and environmental contamination of the bacteria.
Confirmed cases of anthrax in animals are reportable to the Board. A follow-up investigation of these cases is done to ensure local public health and law enforcement officials are aware of the occurrence of anthrax in livestock in the area. BAH staff work with the producer to dispose of the carcass in a way that minimizes contamination of the environment from anthrax and to see that other susceptible animals are removed from the area to prevent further animal exposure to anthrax. Public health staff will interview those who work with infected animals to see if there are any exposures that warrant prophylactic antibiotics.
Treatment
If discovered soon enough, the disease can be treated with antibiotic therapy. Other animals in the herd should be moved off the pasture or away from the area to prevent further exposure to anthrax and consider prophylactic antibiotic treatment. Before returning to the pasture, animals should be vaccinated to protect against anthrax. Infected and exposed animals are quarantined so there is no chance of exposed or infected animals being moved into the food supply.
Prevention
There is an effective vaccine for domestic animals. It is recommended for use on animals where anthrax has been a problem historically. The vaccine needs to be administered annually to maintain its effectiveness.
Human Risk
Humans can develop anthrax after having direct contact with infected tissues or hides, consuming infected meat, or breathing in contaminated aerosols. The type of illness a person develops depends on how anthrax spores enter the body and symptoms can show up anywhere between one day and two months after exposure. While human anthrax is rare and can cause severe illness and death, the disease is generally treatable with antibiotics. People with known high-risk exposures may be prescribed prophylactic antibiotics to prevent infections. Veterinarians should wear gloves, coveralls, and boot covers when handling animals suspected of having anthrax and should wear an N95 mask and eye protection if performing procedures that result in splashes or aerosols.
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