Anaplasmosis had a banner year in the south in 2015, and could rear its ugly head again this year, or the next or the next.
Because insects are one of the disease's vectors, it's hard to prevent, but veterinarians can help clients reduce the spread of anaplasmosis by management techniques.
Anaplasmosis is a disease of the blood caused by the parasite Anaplasma marginale in cattle. It is seen worldwide and reported in at least 40 states. Disease outbreaks can lead to death due to anemia in adult cattle. It can also cause abortions, decreased weight gain and bull fertility problems, not to mention the treatment costs.
A. marginale is transmitted both mechanically and biologically.
Mechanical infection can occur by infected needles, dehorners, ear taggers, castration knives or other surgical instruments. Research has shown six of 10 calves injected with a needle used on a carrier calf will also become infected.
Another mechanical way of transmission is through the infected mouthparts of biting flies such at horse flies and deer flies, and by mosquitoes. Mechanical transmission is short-lived since the parasite cannot survive long outside the body.
Anaplasma can also be transmitted biologically by winter ticks. The ticks receive the parasite from an infected animal and replicate it for up to a year. In that time, they can transmit the parasite to other animals.
The clinical signs of anaplasmosis are most severe in adult cattle. Calves less than one year do not show clinical signs but will become carriers for life. Cattle 1-3 years old will show increasingly more severe clinical signs. Cattle over 3 years old, which are newly infected, will show the most severe clinical signs, and 30-50% will die if not treated early.
The first signs of infection for most cattle are death. However, if cattle are observed frequently, producers may notice them fall behind the herd and not eat or drink. Treatment is necessary early after the disease onset.
There also is a vaccine available, and many producers use antibiotic-treated mineral throughout the fly season; after this year, that practice will fall under the regulation of the Veterinary Feed Directive and will require a prescription by a veterinarian.