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Anthrax – signs and mode of transmission

Anthrax is primarily a disease of herbivores and omnivores such as pigs are much less susceptible. Animals are usually infected by spores produced by the Anthrax bacteria which can survive for years and even decades in the environment. Therefore most infection is caused by contact with contaminated pasture or soil. Consequently pigs housed indoors are highly unlikely to be exposed to Anthrax. Disease occurs when anthrax spores enter the body and germinate, causing multiplication of the bacteria and release of toxins. The incubation period of natural infection in susceptible animals is typically three to seven days but can range from one to 20 days. In herbivores, the incubation period is very short, lasting only a few hours or days and resulting in rapid death without prior symptoms.

One or more sudden deaths in a herd of livestock is usually the first sign of an anthrax outbreak. Clinical signs such as fever, disorientation, muscle tremors, respiratory distress, and convulsions often go unnoticed. In some animals, swelling of the face, jaw, neck, and front shoulders may be observed. Lymph nodes around the neck may also become swollen. The toxins from anthrax bacteria cause internal bleeding. After death, the characteristic signs of anthrax infection are bloody discharge from the nostrils and other natural orifices of the body, rapid bloating, and a lack of rigor mortis. If anthrax is suspected as a cause of death, the carcass should NOT be opened. The tissue, blood, and discharges from an anthrax-infected carcass are full of anthrax bacteria and are dangerous to other animals and humans. Suspect anthrax cases should only be handled by a veterinarian or a trained Canadian Food Inspection Agency ( CFIA ) investigator. A sick animal that is suspected of having anthrax should be isolated and must be reported.

For more information on this disease consult the CFIA website