Many beef producers associate anaplasmosis with horse flies and keep up a prevention program only during the fly season, says Oklahoma State University Extension veterinarian Dave Sparks. Unfortunately, many of these same producers are still experiencing anaplasmosis problems year-round, because biting flies are only a minor vector compared to other ways the disease can be transferred. In many areas, especially wooded or brushy pastures, ticks are more important vectors than biting flies.
Ticks are an all-year problem in much of the South, so the control program also needs to be maintained all year. Stockmen also spread the disease from carriers to susceptible animals by not removing all traces of blood from equipment when processing adult cattle. The organism can be carried by needles, dehorners, castration knives, ear taggers or any other implement that draws blood. It is sometimes possible to determine the source of the outbreak by the way cases develop. When insect vectors are responsible there will usually be one sick animal, followed several weeks later by multiple cases. If human transfer is the cause, several sick animals will show up at the same time two to four weeks after the cattle were worked.
The most popular means of anaplasmosis prevention is the use of mineral mixes that contain chlortetracycline (CTC). When fed at a rate of 0.5 mg per pound of bodyweight, CTC will prevent anaplasmosis infections. It is important to note, however, that CTC is added to minerals for several different reasons, and these other uses require different levels of drug in the mineral. Make sure that the product you choose states on the label that it is formulated at a rate for the prevention of anaplasmosis and gives the specific amount of daily consumption needed to supply that level. The next step is to monitor your herd to make sure that the product is being consumed at the appropriate rate.
For problem herds or as an alternative preventative, a killed vaccine is available in selected states. It may be especially valuable for use in bulls, who often do not consume enough mineral to meet the CTC requirement for their bodyweight. Another control factor is the elimination of carriers. Recovered animals will be carriers of the disease and a source of infection for susceptible individuals. Clear them of the organism with high levels of antibiotics, isolate them from susceptible animals or cull them from the herd.
The signs of the disease include orange coloration of the mucous membranes due to breakdown pigments released from red blood cells that are destroyed. As more red blood cells are destroyed, the animals become slow and short of breath. They may exhibit aggressive behavior due to a shortage of oxygen supply to the brain. Sick animals are about 10 times as infective as recovered carriers are, so it is important to either move them away from their herd mates or, if this is not possible, move the herd mates away from them. If infected cows do not abort, their calves can become infected in utero. These calves will likely not show symptoms but remain carriers for life.
It is popularly believed that anaplasmosis only affects mature animals. Recent information out of Kansas State University, however, shows that young animals can be infected and suffer with the disease, although not as severely as older animals.
Sparks offers these tips to minimize the impact of anaplasmosis:
• Use good sanitation concerning hypodermic needles and surgical instruments.
• Use a preventative such as tetracycline in the mineral or incorporation of a vaccine program.
• Observe cattle regularly for signs of trouble. If you are experiencing anaplasmosis problems, your local veterinarian can help to design a preventative program that is best suited for your location and operation.