Anthrax Update
Anthrax may appear in summer after spring flooding.
Anthrax can infect all warm-blooded animals. Charles Stoltenow, North Dakota State University Extension assistant director and program leader for agriculture and natural resources, says that because of human risks, anthrax is a reportable disease. Cases of anthrax in livestock must be reported to the state veterinarian.
The bacterial spores can lie dormant in the ground for 50-100 years or more, enabling the disease to crop up again.
“The vaccine is very effective and inexpensive. If you live in an area where anthrax has occurred in the past, it’s wise to vaccinate cattle ahead of when you plan to turn them out on pasture,” he says.
“Grazing animals pick up spores when grazing contaminated grass — often in an area that has been flooded,” explains Stoltenow. The most common route of infection is by mouth, but infection can also occur from skin injury or from inhaling spores.
Flooding or drought can create more risk. Pastures may be contaminated by water coming from an area where there were carcasses at an earlier time or when infected carcasses are dumped in streams or ponds. Dry water holes may serve as a source of infection, according to Stoltenow.
Hay infested with spores may cause outbreaks during winter. Anthrax may appear in summer after spring flooding.
“It pops up when you least expect it. Outbreaks often occur when livestock are grazing on neutral pH or slightly alkaline soils. Anthrax can also be spread through skin wounds caused by blood-sucking insects, dehorning or castration,” he says.
“Cattle should be vaccinated annually in endemic areas. Any unexplained sudden death should be investigated. The veterinary diagnostic labs have some really quick tests now that can rule out anthrax or confirm it. Ever since 9/11, 2001, the testing for anthrax has greatly improved, with fast turnaround time,” says Stoltenow.
“If the results of the test are positive, there are guidelines and recommendations on how to dispose of the carcass,” he adds. If it can be properly disposed of before it starts to deteriorate or is scattered by predators and scavengers, the bacteria will be contained and eliminated.
If there is any suspicion of anthrax, do not perform a necropsy. Tissues exposed to the air stimulate spore production. A veterinarian can confirm diagnosis by collecting a sample of blood from the jugular vein to send to a laboratory in a sealed container with ice to keep it cool.
“A sample should be taken as soon as possible after finding a carcass, since isolation of the organism becomes difficult if the animal has been dead for 48 hours or more,” says Stoltenow. Other bacteria may overgrow the anthrax bacillus, resulting in a negative diagnosis.
Dead animals that are opened up (by necropsy or by predators and scavengers) are the primary source of contamination of surrounding pasture areas. The open carcass enables the bacteria to form spores when exposed to oxygen. It is imperative that the carcass be burned completely to ashes at the place where it died, if possible.
Editor’s Note: Heather Smith Thomas is a freelancer and cattlewoman from Salmon, Idaho.