Many Oklahoma beef producers associate anaplasmosis with horse flies, and keep up a prevention program only during the fly season. Unfortunately, many of these same producers are still experiencing anaplasmosis problems year around, 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 many areas of Oklahoma, 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 2 to 4 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/lb. of body weight CTC will prevent anaplasmosis infections. It is important to note, however, that CTC is added to minerals for several different reasons, including use as a growth promotant for yearlings, 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. If not, you may need to look at other products or change your management practices in order to correct consumption deficits. It is very possible to have a few cases even when medicated minerals are provided, because some individuals may not consume them. For problem herds or as an alternative preventative, a killed vaccine is available in selected states including Oklahoma. It may be especially valuable for use in bulls, who often do not consume enough mineral to meet the CTC requirement for their body weight. 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 administered parentally, 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. By the time signs are noticed, the disease is usually far along and you may easily cause the death of the infected animal while trying to bring them in for treatment. If you suspect an anaplasmosis problem contact your veterinarian who can make a definitive diagnosis and recommend a course of treatment before other animals are exposed. 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. This is due to young animals’ ability to produce new red blood cells much faster than adults . In young animals anaplasmosis can easily be confused with bovine respiratory disease because in both instances the animal has a fever and experiences labored breathing. With anaplasmosis, however, the increased respiratory rate is due to a decreased capacity for the blood to carry oxygen rather than to any lung involvement. The two syndromes can also occur together.
If you live in an area where ticks are active in the winter, or you sometimes work your cows in cool weather, using CTC medicated mineral all year can save both the hard work involved with treating active anaplasmosis cases and the losses associated with the disease. Summer cases of anaplasmosis are often more dramatic and associated with more deaths because cattle are not watched as closely as in the winter when supplemental feeding is required. In the summer months it is easy to get involved in farming or haying operations and not check the cattle as frequently as they should be checked. This leads to outbreaks being more advanced and widespread before they are discovered. The disease progresses quickly. With each passing day the number of red blood cells affected by the organism doubles, until the immune system arrests the infection, treatment limits the course, or the animal dies.
In conclusion, beef producers can minimize the impact of anaplasmosis by 1) utilizing good sanitation concerning hypodermic needles and surgical instruments, 2) utilizing a preventative such as tetracycline in the mineral or incorporation of a vaccine program and, 3) observing 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.