What is the treatment of the anaplasmosis protozoan disease of cattle?

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  • 1 decade ago
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    Prevention and control methods should be based on geographic location, exposure to possibly infected cattle, purebred versus commercial herds, and management goals. Complete eradication from herds in northern climates where cattle ticks are not prevalent should be the goal of cattle producers. If this is not done, carriers will remain in the herd and serve as sources of infection that can cause losses at any time in the future. Cooperation of neighbors with infected herds may be necessary, as transmission between herds on nearby pastures readily occurs. A specific plan for control and eradication of anaplasmosis should be worked out with the herd veterinarian.

    Anaplasmosis vaccines are available, but have some disadvantages. In southern states where exposure to infected ticks cannot be avoided, vaccination of exposed, susceptible, or infected herds is often advisable. In northern states, this is usually not recommended since aggressive testing and treatment with antibiotics can eliminate the disease. It is important to remember that anaplasmosis vaccines do not eliminate the infection from a herd or from individual animals. They only prevent the development of clinical disease. Vaccinated cattle that are carriers of anaplasmosis will remain carriers, even though they will not develop the disease themselves. Thus, they may be a source of infection for herd mates that are not vaccinated.

    The first anaplasmosis vaccines caused a problem with nursing calves called neonatal isoerythrolysis. The vaccine contained red blood cell components that caused cows to develop immunity to some red blood cell components. Antibodies in the cow’s colostrum attack red blood cells of newborn calves that inherited these components. The red cells are quickly broken up or lysed, resulting in an acute hemolytic episode that often resulted in death. Herds commonly reported a one or two percent death loss. Refined manufacturing techniques and carefully timed vaccination have largely eliminated this problem.

    Infected herds should be isolated if possible. This prevents spread to other herds and subsequent re-infection of the original herd once disease is eliminated. All replacement cows and bulls should be tested before addition to the herd.

    In northern states, infected, but unidentified carriers can be identified by a blood test of all cattle in the herd. It is best to do this two or three months after the first killing frost. Animals that react to the anaplasmosis test are probably infected carriers and should be isolated and treated with tetracyclines. Testing and treating in late fall or early winter precludes possible further spread by insect vectors. In some situations, it may be easier to treat all cattle in infected herds after a killing frost, rather than just those identified as carriers.

    The carrier state can be eliminated by one of two methods.

    1. Put all cattle on a dosage of 5 mg oxytetracycline or chlortetracycline per pound of body weight daily for 30 days. At this dosage rate, a 1,200 pound cow needs 6 grams daily of the drug. This will eliminate carriers, but it is important that bunk space is adequate, so that all cattle get the required daily dosage. This dose must be recommended by a veterinarian.

    2. Inject all cattle with 9 mg per pound body weight of long-acting oxytetracycline. This treatment must be repeated every third day for four treatments. Some veterinarians feel that three treatments are adequate, but published research trials suggest that four treatments should be used. This procedure is often used in smaller herds.

    In infected herds, anaplasmosis can be controlled in exposed cattle during the vector season by feeding tetracyclines. Add the drug to a small amount of grain or incorporate into a salt/mineral mixture. Intake should be approximately 0.1 mg. per pound body weight per day. Intake must be carefully monitored.

    It is not necessary to provide tetracycline in the salt/mineral mixture of all cattle in northern states. The relatively infrequent occurrence of anaplasmosis and the ability to eliminate the disease by treatment during the winter months precludes routine feeding during the grazing season for most producers. However, if the disease has occurred in the herd or if neighboring cattle are known to be infected preventative treatment may be advisable.

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