Concern was palpable at a public meeting last week where about 175 livestock producers gathered to learn more about an old enemy.
As of July 27, anthrax had killed 324 animals in Saskatchewan and 56 in Manitoba, making this the biggest Canadian outbreak in decades.
Worries about spread of the viral disease led to the cancellation of several livestock shows in north-central and northeastern Saskatchewan, where most of the cases have occurred. Most recently, the exhibition in Prince Albert, Sask., cancelled the livestock show portion of its annual summer event scheduled Aug. 1-5, citing unacceptable risks.
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Risk was the primary concern during the question and answer session at the University of Saskatchewan July 26. Answers were provided by veterinarians Chris Clark of the Western College of Veterinary Medicine and Sandra Stephens of the Canadian Food Inspection Agency, as well as Muhammad Kahn of Saskatchewan Health.
The Farm Animal Council of Saskatchewan, which organized this and two other meetings last week, posted the presentations on its website at www.facs.sk.ca. More details are also available on the CFIA website at www.inspection.gc.ca.
Symptoms
The disease works quickly, Clark said. Once incubated in the animal, anthrax bacteria can kill within two to three hours by producing a powerful toxin that destroys internal systems. Depression and high fever are typical, but occur so quickly that anthrax is difficult to diagnose, Clark said.
Infected animals can be saved using high doses of antibiotics, but only with quick action.
Mature animals seem to be at higher risk, possibly because they do more grazing so they are more likely to ingest the bacteria.
After death, there may be bloody discharge from the nose, mouth, anus and vagina, and in some cases the belly appears swollen. Carcasses of anthrax victims seem to decompose more quickly than ordinary.
The disease is diagnosed through blood or tissue samples. Clark said Bacillus anthracis is easily identifiable under a microscope through its distinctive shape.
“They look sort of like a railway car.”
Spread
Anthrax “is not contagious in the normal way we think of it,” Clark said. It is not passed directly from one animal to another. It spreads most commonly through the soil, where bacteria are ingested by grazing animals. Cattle appear most susceptible, followed by sheep, bison, deer, horses, goats and pigs.
The disease is unlikely to be spread by feed, Stephens said, unless the feed contains anthrax contaminated soil. She considers the risk of spread at livestock shows to be low.
Infection in humans is rare and mostly of the skin variety, which is highly treatable, Khan added. People cannot get the ingested form of anthrax unless they eat meat from an infected animal. That would not happen under current safety regulations, he said.
Anthrax is a reportable disease and the CFIA is involved in destroying all infected carcasses.
Visitors to areas contaminated with anthrax or potentially so should thoroughly wash and disinfect footware.
Control
Vaccination with a modified live vaccine, the Sterne vaccine, is the control for all animal species. Stephens said supplies are reported to be sufficient. Each one cc dose costs $2 to $2.50 and provides protection for six months to a year.
The vaccine takes effect within eight days, with full protection gained within two to three weeks, Stephens said. Antibiotics will interfere with the vaccine and should not be administered within eight days on either side of the vaccination.
In risk areas, animals of all ages should be vaccinated. Cows do not pass immunity to unborn calves, said Clark.
If the animals are on highly contaminated premises, a booster dose should be given two to three weeks after the initial vaccination.
The CFIA provides an initial single dose of vaccine for each animal on contaminated premises at no cost to the owner.
Stephens said the CFIA recommends that all herds within 10 kilometres of an infected area be vaccinated. However, producers should consult with veterinarians about vaccinating particularly if their pastures and conditions are similar to those of contaminated farms.
Animals in areas with an outbreak should be vaccinated annually for three years, she said.
There is a 42-day withdrawal time before vaccinated animals are safe for slaughter.
Disposal
Control of anthrax demands careful handling of infected carcasses, Clark said. Exposure to oxygen causes anthrax bacteria to produce spores that are easily spread, so carcasses should not be opened.
Burning is the preferred method of disposal. Deep burial is also an option. Carcasses should be protected from scavengers that might damage, eat and spread them.
The CFIA pays an indemnity to the owners of animals dead of anthrax: $500 each for cattle; $350 for horses and $100 for sheep, goats and swine.
