Anthrax is an ancient and deadly bacterium for people and livestock
Published on March 21, 2020
Anthrax is one of the oldest killers of humans and livestock. It is mentioned in some of the earliest recorded history, several thousand years ago, and has been called by many names, including splenic fever, charbon, milztrand and woolsorter’s disease.
Anthrax is caused by the bacterium Bacillus anthracis and occurs sporadically in the U.S. and Canada. This disease is seen worldwide, and associated with sudden death of cattle and sheep, though it can infect all warm-blooded animals.
Because of human risks, anthrax is a reportable disease. Cases of anthrax in livestock must be reported to the state veterinarian or animal health agency.
South Dakota State Veterinarian and Executive Secretary and South Dakota Animal Industry Board Member Dr. Dustin Oedekoven says there are usually some cattle herds in South Dakota affected with anthrax every year.
Vaccination is key
“In nearly all cases, the cattle had not been vaccinated. We continually remind cattle producers anthrax exists in our area. It’s difficult to predict when and where we might see cases, so vaccination is the best prevention,” he says.
The vaccine is readily available and affordable.
“When we see losses in a herd, there are generally multiple animals dying,” he explains. “The cost of annual vaccination is cheap insurance against the possibility of losing several animals to anthrax, the cost of the disease is much greater than the cost of vaccine.”
“We commonly see anthrax in South Dakota and occasionally in other surrounding states. A few years ago, there were several herds affected in Colorado. There have also been cases in cattle in Texas, Montana and Wyoming,” he says. “There were outbreaks a few years ago in bison in Montana, and there are periodic outbreaks in wildlife in Texas.”
“People sometimes become complacent, especially if it’s been several decades since the disease occurred in their area, but it can crop out any time, so it’s good to include it in spring vaccinations,” Oedekoven stresses.
“Annual vaccination is protective and can be given in the fall if that’s the only time the rancher can vaccinate,” says Oedekoven. “Spring vaccination is probably best since summer is the riskiest time for this disease.”
Anthrax spores can survive for many years, causing disease when conditions are right.
“Some of those conditions include heat and high humidity. We often see anthrax when we have flooding or drought,” he says. “Pastures may be contaminated by water from an area where there were infected carcasses at an earlier time.”
He continues, “Low-lying ground or marshes are readily contaminated by flooding. Stagnant water holes, as the area dries up again, may serve as a source of infection.”
“When grazing animals have exposure to alkaline soils, where the spores live quite well, they may pick up spores while grazing,” he says. “Hay contaminated with spores may account for outbreaks during winter, though anthrax is usually a warm weather disease. It will generally crop up in summer after springtime flooding.”
“The spores usually are picked up through the mouth,” says Oedekoven. “Anthrax can also be spread through skin wounds caused by blood-sucking insects, dehorning or castration.”
He continues, “Outbreaks have also occurred because of contaminated feed, such as bone meal, meat scraps or other animal protein products, but current regulations for manufacture and importation of these products eliminates these as a source of infection in this country.”
Ruminants seem to be most susceptible to this disease. The rumen is a perfect environment for anthrax bacteria to incubate and start releasing toxins.
“Anthrax is sometimes seen in deer, elk and other wild ruminants in certain regions from the Gulf of Mexico to the Northwest Territories of the Yukon,” says Oedekoven. “It is thought to have existed long ago in the bison herds that grazed these areas.”
Anthrax is generally not spread from live animal to live animal but is transmitted via spores in soil that have been contaminated by the carcass of an animal that died from anthrax. Other animals may contract the disease by licking the carcasses of animals that died of it.
“Flies feeding on carcasses that died from anthrax can pick up blood and pass it on to the next animal they feed on,” Oedekoven says.
The spores vegetate in heat and humidity. The bacteria come to life and start reproducing in the animal, releasing toxins.
“The result is system-wide bleeding and rapid death,” he says. “Most animals are not found in time to treat, they are simply found dead.”
“After the animal dies and the carcass is opened, the bacteria are exposed to the air and they form spores,” he explains. “These spores are very resistant to heat, cold, freezing, chemical disinfectants or drying and can survive in contaminated soil for 100 years or more in the right conditions.”
Oedekoven continues, “The original infected 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.”
“We recommend any time a producer has death loss in the herd to consult with a veterinarian, especially if multiple animals died without an obvious cause,” he stresses. “Don’t necropsy the animal, a veterinarian can take a blood sample for testing first, if anthrax might be a possibility.”
“Today, the lab can do a rapid test to determine if it is anthrax or not. We don’t want the carcass opened because that will release more bacteria into the environment and allow more contamination and spread of the disease,” says Oedekoven.
“We want to dispose of a carcass quickly so there won’t be flies landing on it, and so there’s no chance for wildlife or other animals to drag the carcass around,” he notes. “In South Dakota, we have a state law requiring burning and burying carcasses that are known or suspected to have died from anthrax.”
He notes if a producer ever suspects anthrax, it’s wise to contact a veterinarian immediately.
Heather Smith-Thomas is a corresponding writer for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.