Anthrax does not easily spread by direct contact between animals. Animals are usually infected by ingestion of the soil-born anthrax spores which then revert to the vegetative form reproducing within the infected animal. Spores can be picked up directly from soil through grazing or from feed grown on infected soil. When periods of drought cause animals to gaze closer to the ground, animals may be more likely to ingest spores. Flooding and working the land are also associated with an increased incidence of ingestion. Although rare, it is possible for animals to inhale dust harboring anthrax spores. They may also develop a localized infection through breaks in their skin.

Clinical Signs – Ruminants such as cattle and sheep are the animals most susceptible to anthrax, and are most commonly affected, followed by horses and then swine. In ruminants, the disease is most commonly characterized by sudden death. If detected immediately, clinical signs include fever, muscle tremors, respiratory distress, and convulsions. After death, there may be bloody discharge from body orifices, rapid bloating and, notably, a lack of rigor mortis. If horses ingest spores, they usually show signs of colic, enteritis, and fever. If anthrax is introduced through a break in the skin, localized swelling at the introduction site and generalized swelling at the neck and chest are common.

Treatment - B. anthracis is susceptible to a number of antibiotics including penicillin and oxytetracycline. Because of the rapid course of the disease, these antibiotics must be given immediately when infection is diagnosed.

Control and Prevention – Because of the human health risk and the highly resistant spore forming potential of anthrax bacteria exposed to oxygen, when anthrax is suspected, do not open dead animals for routine examination. A veterinarian can confirm anthrax by taking a blood sample from a peripheral vein and submitting it to the California Animal Health and Food Safety Laboratory. All suspected cases of anthrax must be reported to the California Department of Food and Agriculture or the US Department of Agriculture. Quarantine of the area may be necessary to prevent further spread of disease. Dead animals should be burned where they are found or buried with lime at least 10 feet deep.

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