Cattle producers and veterinarians have their own lingo that just doesn't register with most people from the outside world. This is especially true for cattle diseases. Scours, red nose, and black leg are all terms that we take for granted, but just thoroughly confuse most others. But use the term anthrax in a sentence when talking to non-cattle folk, and you will probably get some attention.
Probably rightfully so. Anthrax, of course, has been used as a bio-weapon, and continues to be a very current concern for those tasked with preventing terrorist attacks on our soil or against our troops overseas. But veterinarians and cattle producers have a different slant on this disease agent, and have firsthand knowledge of the death losses it can bring to cattle herds. This past week, we learned of North Dakota's first cattle anthrax case of the season, in the southwest corner of that state.
The bacteria that causes anthrax, Bacillus anthracis, has developed the ability to form a very resistant spore that can survive in the soil over many years of Dakota winters and summers. What this means is that if the disease was present at any point in history somewhere, it's likely still there. If the soil containing those spores gets disrupted by excavation, or by flooding and subsequent drying, those spores could come up to the surface and present themselves to the cattle grazing those locations. When the conditions are just right (high temperatures, humidity, moisture, etc.), more of these spores become active. As a result, we normally see clinical anthrax cases in the hot summer months.
Once the spores have been eaten by the cow, they get through the gut wall into the local lymph nodes, where they really take off and grow, eventually becoming distributed throughout the body. Eventually the bacteria produce several toxic substances that result in shock and a rapid death for the animal. While many of our animal diseases have an incubation period of days or weeks, the incubation period for anthrax could be measured sometime in hours! Most often, the only sign noted with anthrax is simply cattle being found dead on the pasture.
Despite the persistence of the spore in the soil over time, the location of losses due to anthrax is not always predictable. Most areas of North and South Dakota have experienced cattle death losses due to anthrax at some time in the past, which makes it a real possibility at any point in the future. However, not all of these locations experience losses every year, and cases may show up in very different locations from year to year. Weather conditions play a role, as does the vaccination status of cattle grazing those areas. Especially important this year is the fact that some of our pastures throughout the region have experienced flooding or standing water. When the water recedes, those once-wet areas may be places where spores are now washed up and available to be eaten by an unsuspecting animal.
But there's one thing we can reliably predict about anthrax in South Dakota, and that's the fact that it will show up somewhere this summer. In six of the past eight years, anthrax has been diagnosed somewhere in the state. We're lucky in that we have a very good tool to prevent anthrax in cattle, and that's the anthrax vaccine. It is inexpensive and widely available from your veterinarian. One dose prior to turnout to summer pasture protects animals throughout the grazing season.
If cattle are already out on summer pasture and it's too late to feasibly vaccinate them, producers then need to be vigilant about death losses on pasture. When producers are confronted with unexplained death losses of cows or bulls on pasture, the carcass should be left undisturbed until a veterinarian can take an appropriate sample. An animal that has died from anthrax can be a substantial source for new spores in the environment if it is opened up or moved, so consult with your veterinarian first. The nature of this disease is possibly the most important reason that sudden, unexplained death losses in cows or bulls on summer pasture should be investigated by your veterinarian.