Anthrax is one of the oldest killers of humans and livestock and was mentioned in some the earliest recorded history several thousand years ago. It has been called by many names, including splenic fever, charbon, milztrand and woolsorter s disease.
While the last major outbreak in Western Canada was seen in 2006, weather conditions during the summer of 2011 were conducive for disease reappearance and spread.
Anthrax is caused by the Bacillus anthracis bacterium, and occurs sporadically in the United States and Canada. This disease is seen worldwide, and is associated with sudden death of cattle and sheep, though it can infect all warmblooded animals.
This acutely contagious and deadly disease generally is not spread from live animal to live animal, but is typically transmitted by spores found in the carcasses of animals that died of the disease. Animals at pasture usually acquire the disease by ingesting soil/dust (with the vegetation they are eating) contaminated with anthrax spores.
The organisms within an animal s body or bodily secretions can be readily destroyed by ordinary disinfectants or pasteurization/ high heat. But once the animal dies and the carcass is opened and the bacteria are exposed to the air, they form spores. These spores are resistant to adverse conditions (such as heat, cold, freezing, chemical disinfectants or drying) and can survive in contaminated soil a long time. The carcass may be long gone torn apart by predators and scattered, or decomposed and disappeared many years ago, but the spores are still viable in the surrounding soil.
Tasha Epp, a professor at the Western College of Veterinary Medicine in Saskatoon, was involved in a study of anthrax during an outbreak in Western Canada (Saskatchewan, Manitoba, and Alberta) in 2006.
My area of expertise is epidemiology, so I was looking at what happened and where it happened, and some of the interesting factors associated with that outbreak, she says.
What we found in 2006 was that areas with heavy rainfall and flooding in the spring and then dry conditions later in the summer, were more likely to see cases of anthrax. When the areas that were flooding started to dry out in the hot weather, we started seeing anthrax.
This is pretty typical. Moisture draws spores from the ground and then when the flooded areas dry out the cows go back into those areas where there s lush grass, and ingest the spores that end up on grass. That combination of wet, then hot and dry, makes a bad year for anthrax. Many regions experienced that weather pattern in 2011, so ranchers should be aware of the risks for anthrax.
THE 2006 OUTBREAK
In 2006 in Saskatchewan more than 800 animals were confirmed with anthrax. Epp says the Canadian Food Inspection Agency (CFIA) keeps track, because it s a reportable disease, and has records back to 1912 for Saskatchewan. The 2006 outbreak was the largest ever recorded.
Every few years, and sometimes a couple years in a row, there are reports of anthrax on farms, but not to the extent we had in 2006, Epp says.
Cattle seem to be one of most prominent species in which it shows up, but bison were also hit hard in 2006. We hadn t seen it much in farmed bison in the past, perhaps because bison farming wasn t so large in earlier years. Now that we have more bison farms, we saw a lot of anthrax in bison in 2006. On many of those farms we saw many more deaths than we would have seen with cattle, Epp says.
This disease probably affected bison in North America long before there were cattle. Epp says a researcher in Florida has been looking at the potential distribution of anthrax spores in Mexico, the U.S. and Canada. He has mapped it out, and a lot of it seems to follow old cattle trails and bison migration routes where animals died in years past.
Along with beef and bison, Epp says there were a few cases of anthrax found in pigs, horses, sheep and goats in 2006. Basically any warm-blooded animal that grazes can become exposed, she says.
CURE ALMOST IMPOSSIBLE
Most anthrax cases are not found in time to treat. The animal is usually found dead because there is such a fast onset of disease. Some have tried treatment with antibiotics and penicillin is effective, but has to be given in very early stages.
Usually when an animal is diagnosed with anthrax, the CFIA takes charge of how the case will be handled on farm.
The CFIA s anthrax control program utilizes quarantine, vaccination and proper disposal of carcasses to prevent further spread of the disease. Quarantine is placed on all farms where a positive laboratory diagnosis has been made for any animal that died on those premises. The district veterinarian will determine the area to be included in the quarantine based on environmental and geographic conditions. This quarantine restricts movement of susceptible animals on and off that farm.
All susceptible animals on the farm must be vaccinated. The CFIA provides enough vaccine for the initial dose. The quarantine is released following vaccination, 21 days after the last death associated with anthrax.
On any farm that has ever lost an animal to anthrax, the CFIA recommends annual vaccination of all animals.
The vaccine is effective, but because we don t see cases very often, most ranchers don t vaccinate, says Epp. If there was a way to predict where and when anthrax would occur, so people would know which year they should vaccinate perhaps more people would do it. Even in 2011, when we ve been saying there s risk because of the flooding, and heat, many people don t take preventative measures, she says.
It takes seven to 14 days to gain immunity after vaccination. In some instances, one vaccination may not be sufficient. A veterinarian may recommend a booster especially if it s a high-risk year.
An Australian research paper looked at whether vaccination would be quick enough to prevent disease in cattle once cases are seen in a certain region. They seemed to think it would, but vaccination is a voluntary thing.
If your neighbour is having a problem and you know about it, the best way to protect your cattle would be to vaccinate them, says Epp.
The CFIA reminds ranchers in some situations animals may still die of anthrax up to 14 days following vaccination. Thus all animals should be checked twice a day for at least 14 days after they ve been vaccinated. The CFIA reimburses producers for animals lost to anthrax, but deaths occurring more than 14 days after vaccination should be investigated for other causes because indemnity will not be paid unless anthrax is confirmed.
Proper disposal of carcasses through incineration is part of the prevention/control program, to reduce or prevent further contamination of the environment with anthrax spores. Owners should check their animals often and try to find carcasses as soon as possible.
When anthrax is suspected, precautions should be taken immediately until a negative laboratory diagnosis is received or the carcass is disposed of in accordance with CFIA guidelines. The guidelines recommend wearing gloves when handling a carcass, plugging all carcass body openings (anus, mouth, nose) with an absorbent material such as cotton to prevent leaking of fluid. The animal s head should then be covered with a sturdy plastic bag secured behind the ears with duct tape or tied. To move a carcass, it should be placed on material that can be burned with it or easily cleaned and disinfected. The carcass must be covered with a tarp or some other material to prevent scavengers from tearing it apart and to prevent spread of anthrax spores by insects, birds or other animals until the carcass can be burned.
To burn it, there must be enough fuel (wood, or straw bales, or other flammable material) for complete burn, to reduce the entire carcass to ashes. The CFIA must be able to check the burn site to make sure there was adequate incineration of the carcass. If burning is not feasible, deep burial may be permitted. For more details about regulations and recommendations, contact your district veterinarian or the CFIA.
HeatherSmithThomasrancheswithher husbandLynnnearSalmon,Idaho.Contact herat208-756-2841