Animals that develop the clinical signs of anaplasmosis are usually older than a year, and the signs usually begin with a fever of about 104 degrees F. or above. The red blood count can fall very rapidly and animals can become severely anemic in just a few days. As the anemia progresses the animal gets weak, reduces or refuses feed intake, and becomes lethargic. Their gait may become wobbly. Lack of oxygen to the brain resulting from anemia may cause them to act aggressively or behave abnormally. Cows in advanced pregnancy may abort. Often the farmer doesn't notice signs of the disease until he sees a very weak cow or finds one that has died. Cows in advanced stages of the disease may die when they are handled for diagnosis or treatment. In one recent Ohio outbreak, two abortions preceded the first adult cow's death and a total of four of 50 cows died over a period of about two weeks.
Treatment with injectable tetracyclines will usually halt an outbreak in a herd and may prevent the development of severe anemia in an animal already incubating the disease. However, one or two injections will not prevent newly infected animals from becoming carriers. In fact, there are no products currently available that are labeled for the elimination of the carrier state. Elimination of the carrier state with injectable or oral tetracycline antibiotics may be successful with prolonged treatment under the direction of a veterinarian. These carrier animals represent a continual source of infection for their herdmates and potentially for other herds in the area.
In Ohio, the disease is usually reported in the late summer and early fall following periods when biting flies are most active. However, it may occur any time of the year if contaminated needles or other instruments transfer blood from a carrier animal to susceptible animals. It seems to be most frequently reported in beef cattle, but dairy cattle are also susceptible and the disease has occurred in at least one dairy farm in Ohio in the past. Carrier animals are responsible for moving the disease to uninfected herds and regions. If farmers believe that their herds are not infected, it would be well to consider testing for this disease in purchased animals.
OSU Extension, Morgan County and Morgan SWCD will host a meeting on the topic on Tuesday, Dec. 11, 7 p.m. at the Morgan H.S. auditorium. Shulaw and John Groah, Morgan Veterinary Services, will explain what the disease is, how it spreads, what to look for and how to deal with it. Directions: take SR 60 from Marietta or Zanesville to McConnelsville and turn South on SR 376 for 3.2 miles to the Morgan High School.