Anthrax
This article written by Dr. Reynold Bergen, BCRC Science Director, originally appeared in the August 2013 issue of Canadian Cattlemen magazine and is reprinted with permission.
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Anthrax is a soil-borne disease that occurs sporadically in western Canada, especially after floods or during hot, dry weather. Ask your veterinarian whether vaccination is recommended.
Anthrax is a reportable disease in Canada. If anthrax is suspected,
- DO notify your veterinarian
- DO remove surviving animals from the pasture
- DO try to prevent scavenging
- DO NOT move dead animals
- DO NOT call for deadstock pick-up
- DO follow the veterinarian’s instructions regarding deadstock disposal
Cause
When the anthrax bacterium is exposed to air, it forms inactive spores that can survive in the soil for decades. Animals get infected when they consume contaminated soil, feed or water. The spores “germinate” into active bacteria in the animal, and cause death within hours. The bacteria multiply in the carcass, which bloats and decomposes very rapidly. Spores are formed when blood containing anthrax bacteria leaks from body openings and is exposed to air. More spores are formed if the carcass is opened through a post-mortem or scavenging. If the carcass is protected from scavenging and reaches a high temperature, such as under plastic, the bacteria will die off without forming spores. As unburied carcasses decompose, the anthrax bacteria are exposed to air and form spores.
Animals crowded into dry spots during a flood may churn the soil and consume spores. Soil erosion can also expose and move anthrax spores. Spores concentrate in low spots when floodwaters evaporate and infect cattle that drink standing water. During droughts, animals graze closer to the ground and may consume soil. Contaminated feed and soil excavation can also spread anthrax. Anthrax is most common at 20°C or higher; cases in Western Canada since 1999 have mostly occurred from July through mid-September, and have followed periods of hot and dry or hot and wet weather.
Symptoms
Animals may appear weak, feverish or excited, then become depressed, uncoordinated, have difficulty breathing, and convulse. Animals die very quickly, so dead cattle (perhaps with a bloody discharge) are usually the first sign of anthrax.
Disease response
Call your veterinarian. Post-mortems can cause more soil contamination, so the veterinarian will draw a blood sample from a dead animal instead. If the sample tests positive for anthrax, the Canadian Food Inspection Agency will be notified. The provincial agriculture department may also be notified. The CFIA no longer investigates, tests, quarantines, vaccinates, or assists with anthrax mortality disposal, but some provinces pay for diagnostic anthrax tests and provide advice on proper disposal and control.
Vaccination and Treatment
Anthrax is susceptible to most antibiotics, so prompt treatment of animals at the earliest sign of illness should be effective. Antibiotics counteract the vaccine, though. Do not treat animals with antibiotics if they have been vaccinated less than 2 weeks previously, and do not treat with antibiotics if you plan to vaccinate them within the next 2 weeks.
Deadstock Disposal
Proper disposal helps limit the spread and recurrence of anthrax. Follow the advice of a provincial government veterinarian or your private veterinarian when disposing of anthrax carcasses. Wear gloves and long sleeves if it is unless absolutely necessary to handle or move the carcass. Anthrax does not naturally disperse in the air, so a breathing mask isn’t necessary.
Incineration destroys anthrax spores. Your veterinarian can tell you if incineration is legal in your area, recommend the best fuels to use, and the safest way to manage the incineration.
Burial: If intact carcasses are buried early, they will decompose naturally and kill the bacteria (but not spores). Do not bury carcasses in flood-prone areas. These areas will flood again, and spores will return to the surface. The bottom of the burial pit should be three feet above the water line.
Natural disposal and deadstock pickup both increase the risk of future anthrax outbreaks by spreading the spores over a wider area.
Thoroughly wash your hands and arms when you are done, wash your clothing, and disinfect your boots.
Danger to Humans
In rare cases, producers or veterinarians handling infected cattle may be infected through a cut or skin abrasion. Symptoms generally appear within 7 days of exposure. A raised itchy bump like an insect bite appears and develops into a painless ulcer (1-3 cm in diameter). A black spot appears in the center within 2 days, and adjacent lymph glands may swell. Immediately contact your doctor if this occurs. There is about 20% mortality if untreated; mortality is rare if treated with antibiotics. The disease is not known to spread from person to person.
Vaccination
Vaccination may be recommended if anthrax has historically occurred in your area, or in an area you purchase hay from. Producers can obtain the vaccine through their veterinarian, who can order it from a supplier. The vaccine costs about $2.00 per dose.
Learn more
Anthrax
Canadian Food Inspection Agency
Changes to the CFIA anthrax program
BCRC Blog – June 3, 2013
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