It is easy to be taken by surprise by anaplasmosis. Although the problem can occur any time, it is usually most prevalent in the mid to late summer. This is a time when many stockmen are busy in the hay fields or with other projects and are not checking their cows every day like they do during winter feeding. This year, however, anaplasmosis season is likely to come early due to the influence of a mild winter and early spring on the insect vectors that carry the disease.
Anaplasmosis is caused by a single cell parasite that lives inside the cow’s red blood cell. When the immune system recognizes the problem it destroys the parasite, but unfortunately destroys the red blood cell at the same time. When a significant number of red blood cells have been destroyed anemia results and weight loss, abortion and death occur. The parasite can infect calves but cattle less than one year of age will not usually show symptoms. Cattle between one and 3 years may show mild to moderate symptoms of the disease, but death rarely occurs in cows less than three years of age. Biting insects such as horse flies and ticks carry the organism from infected or recovered carrier cows to healthy cattle. In this type of transfer it is common to see one cow with the disease, followed a few weeks later by an outbreak of several more cows that were infected from the original case. The organism can also be spread by blood on needles, ear taggers, dehorners, or other instruments. This type of transfer typically results in an outbreak of several cases simultaneously.
Although oxytetracycline is an effective treatment, in many cases by the time that the disease is seen and diagnosed, the anemia is so severe that gathering and treating the animal can result in death due to lack of oxygen. Active cases should be isolated, but in some cases it is better to move the healthy animals than to stress the infected cow. The best course of action is a good preventative program. Feeding a mineral supplement that contains chlortetracycline is effective except for cows that do not eat their share of the minerals. Bulls often have trouble when medicated mineral is fed because they do not eat enough of the product on a body weight basis. For animals that do not eat enough minerals, or if feeding medicated mineral is impractical, there is a vaccine that is produced in Louisiana that can be used by permission of the Oklahoma State Veterinarian. For more information on this limited use vaccine, visit with your local veterinarian.
Put the preventative program of your choice in place now and check your cows regularly looking for atypical behavior and animals that are pale or yellow around the eyes. Don’t let anaplasmosis rob you of your summer profits.
Source: Dave Sparks DVM, Oklahoma State University Area Extension Veterinarian