S.D. herd loses 13 head to anthrax
August 25, 2017
In the first case the state has seen this year, anthrax killed 13 head of cattle in a southeastern Pennington County herd earlier this month.
The cattle were moved to a different pasture and vaccinated for anthrax when a veterinarian with the state confirmed the disease with a field test. The cattle owners first discovered problems on Tuesday of last week and by Friday an initial diagnosis was made. Eleven cows and two bulls died as a result of the infection. South Dakota state veterinarian Dr. Dustin Oedekoven figures because the cattle owner has now treated and vaccinated susceptible cattle, that further death loss in the herd is unlikely.
After a notably dry summer, much of the state received rain last week. Oedekoven said his theory is that the rain mixed up the soil, which had been unusually dry, moving spores to the surface where they were exposed to grazing cattle. The rain didn't activate the spores, but it could have made them more accessible.
"They are grazing on short grass and we had rain stir up the soil," he said. Excavation work earlier this year on a water line may also have contributed to greater risk of anthrax exposure in this pasture.
When the spores are ingested, the bacteria begin dividing and goes systemic. "It causes bleeding in multiple organs and then they die."
Often anthrax prevents blood from clotting, but not always. One commonly seen sign associated with anthrax cases are carcasses with unclotted blood oozing out of the orifices – nose, mouth, and anus. "We try to collect a blood sample from the jugular vein (of a suspect carcass). A lot of times you can get a sample even if it's been dead a day or more because the blood hasn't clotted. If it has clotted, it seems to be less likely to be anthrax."
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Several blood samples have been submitted by "alert veterinarians" this summer, but all have been negative until now, he said.
Dr. Oedekoven said he's hoping this is a one-herd event, but that there is no way of knowing if or when other cases will pop up.
"It's a difficult disease to predict where we might see it," he said, adding that often dry conditions do tend to lead to increased anthrax situations.
Anthrax is a bacteria that exists in spore form in dirt for a long time. According to the Center for Disease Control, the spores can survive for "decades" in the soil.
Cattle and other grazing animals can become infected by ingesting or inhaling the spores. Dr. Oedekoven said that in dry years, this becomes more of a concern because grass is shorter, creating more of an opportunity to graze close to the ground. Oedekoven said that in 2005, 55 herds up and down the Missouri River were confirmed infected with the disease. "That is the worst year I recall. It was another bad drought year. There were far more cases in Minnesota, North Daktoa and Manitoba. That was a bad year."
The bacteria is not contagious, "which means you can't catch it like the cold or flu," said the CDC, but Dr. Oedekoven warns those dealing with carcasses to always wear protective clothing including long sleeves and gloves. A veterinarian in South Dakota was once infected with the skin form of anthrax after dealing with an infected carcass. "It was treated with antibiotics but it's potentially deadly and you don't want to risk it," he said.
Any warm blooded animal can contract anthrax, Oedekoven said, but it is most often seen in cattle, bison and sometimes sheep because those animals are most likely to be grazing close to the ground where the spores naturally exist. Scavengers including wild animal or pet dogs can also become infected from affected carcasses. Biting flies may also serve to spread the disease in an affected herd.
Everyone in the livestock industry experiences death loss and all carcasses should be properly disposed of on the farm and ranch, which means burning or burial, said Oedekoven. "Burning is obviously not a good option now due to the dry conditions, so people should have a designated site where you know your death losses are going to go," he said.
Burying carcasses helps prevent predators from transferring disease between herds and helps prevent anthrax spores (from anthrax infected carcasses) from seeding the ground. "After the bacteria come into contact with oxygen, they turn into the spore and are seeded into the environment. We like to keep carcasses intact and get them burned and buried as quick as we can and then sanitize the area."
Dr. Oedekoven recommends annual vaccination for anthrax, particularly for cows and bulls. Calves are less likely to become infected because they are less aggressive grazers.
"Spring is the best time to vaccinate cows but if they can't get it in the spring, fall works." He said that if there is a pasture with a history of anthrax, producers might consider vaccinating just prior to turnout into that pasture, but all decisions should be made in consultation with the local veterinarian.
Good range management strategies are another way to help decrease the likelihood of anthrax infection. "Make sure your pastures aren't overgrazed," he said, admitting that that can be a challenge in a dry year like this one.
If you suspect anthrax, contact your local veterinarian. If anthrax is confirmed, your veterinarian will report the confirmed anthrax case to the state veterinarian, who will issue quarantine.
No movement of animals onto or off of the affected premises is permitted during the quarantine period. The quarantine will be released by the Animal Industry Board 30 days after the last affected carcass is properly disposed of, according to the Animal Industry Board.