By: Russ Daly, DVM, South Dakota State University
Cattle producers have been hearing more and more about a disease called anaplasmosis. This disease recently appears to have become more common in areas not previously affected. The disease is typically associated with cattle herds in warmer areas of the country, but is it ever a problem up here on the Northern Plains?
Anaplasmosis is a bacterial disease that affects red blood cells of cattle. Once a red blood cell is infected with the germ, the animal’s body recognizes it as abnormal and destroys it. If an excessive number of red blood cells are infected and removed, anemia results. The blood is no longer able to adequately supply oxygen to the body’s cells. Anemia appears as weakness, rapid breathing, pale mucous membranes, and – if severe – collapse and death, especially when the animals are exerted. These signs almost exclusively happen in adult cows or bulls; calves can be infected but rarely show outward signs.
Antibiotics, typically tetracyclines, are approved to control the disease in infected beef cattle (medication options are more limited for lactating dairy cattle). The medication keeps the infection down to the point where clinical disease is less likely, but it doesn’t cure a persistently infected animal from the infection, nor does it prevent a susceptible animal from becoming infected.
As a disease of blood cells, anaplasmosis is spread through transfer of blood. In areas where the infection is maintained, this occurs through tick bites. The bacteria can also be spread mechanically by biting flies and instruments such as needles carrying blood between animals.
Anaplasmosis persists in cattle herds in certain parts of the country. This persistence, or “endemic” nature, of the disease, needs two things: a vector (tick) population that is active throughout most of the year, and a population of persistently infected cattle. Tick activity serves to move the bacteria from infected cows and bulls to non-infected animals – oftentimes calves. What’s more, persistently infected cows can give birth to calves that are persistently infected. Unless the infections are extensive enough, or infected animals are placed under sufficient stress, signs of illness might never occur.
Presence in Northern Plains
In the Northern Plains, neither one of those factors are yet present. Tick populations are active for a relatively short time period, and more importantly, there is not a resident population of infected cattle for which to serve as a source of the bacteria.
That doesn’t mean anaplasmosis doesn’t occur here. Every year, anaplasmosis-positive cattle are found in South Dakota. Usually these are cattle that have been transported here from endemic areas of the country. These animals can succumb to clinical signs if exerted or extensively infected, and can play somewhat of a role in transmission. Biting flies or vaccine needles can spread the bacteria to susceptible herdmates, resulting in local outbreaks. The conditions here, in contrast to those in the Southern US, are not hospitable for the infection to become well-established in our herds, however.
Even though anaplasmosis is not yet endemic here, cattle producers bringing animals in from those endemic areas should be aware of its potential, and ask their veterinarian for advice prior to purchase. A vet-to-vet inquiry about the anaplasmosis status of prospective purchases is a good idea, as is blood testing of animals imported from those areas. Blood tests for anaplasmosis are good for screening, but false positive results can occur. A PCR test can be used to confirm infection status.
If a beef producer finds himself with positive cattle, a good practice would be to isolate them from the rest of the herd to minimize the possibility that biting flies or needles could spread the infection to the herd’s susceptible animals. In dairies, changing needles and palpation sleeves after working with infected animals is recommended.
The Bottom Line
Is anaplasmosis a problem on the Northern Plains? A reasonable answer is, not too much - yet. However, other vector-borne diseases (vesicular stomatitis, for example) have popped up in our neighborhood when the conditions become favorable. Keep tabs on anaplasmosis and other emerging disease issues through conversations with your veterinarian and extension livestock specialist.