The mild winter and early spring in many parts of the country created favorable conditions for insects and other vectors of disease such as anaplasmosis, specialists warn. Glenn Selk, Oklahoma State University Extension emeritus animal scientist, drawing on information from veterinarian John G. Kirkpatrick, says any blood-sucking insect can be a potential carrier of the disease. Ticks and horse flies are often the most common culprits. Cattle-working tools such as castration knives and vaccination needles also can transmit the disease. Anaplasmosis is an infectious disease of cattle caused by a rickettsia organism, Anaplasma marginale. Clinical signs of anaplasmosis are related to the age of the animal. Calves under 6 months of age become infected but rarely show clinical signs and remain carriers.
A carrier animal may or may not give a positive reaction to serologic tests for A. marginale. However, the carrier’s blood is infective for the susceptible animal. Yearling to 18-month-old cattle will develop symptoms, and while the clinical signs are mild, these animals become carriers. In adult cattle, clinical signs include depression, off feed, fever up to 107° F, anemia, paleness and/or yellow mucous membranes, rapid respiration, yellowish urine, occasional belligerence, dehydration, constipation and sudden death. Most deaths occur in the later stages of the developmental stage or early convalescent stage.
Selk encourages ranchers to work with a veterinarian to develop a prevention and treatment program. Anaplasmosis is a herd problem and should be approached as such. Outbreaks occur when there is no control program, anaplasmosis carriers and susceptible animals are present in the herd, and mechanical or biological vectors for transmission are present.
Anaplasmosis control is based on preventing the transmission of infected red blood cells from carrier animals to susceptible animals. Strategic environmental management, insecticides and repellents, cleanliness of surgical instruments and changing of needles between animals are practices that must be in place to minimize disease transmission.
Chlortetracycline consumed at the rate of 0.5 mg-per-pound of cow bodyweight daily during vector season will help prevent transmission of anaplasmosis. CTC may be administered in medicated feed, salt-mineral mixes offered free choice and medicated blocks. It is imperative to monitor consumption levels, as effectiveness is dependent on proper intake. Be certain that the mineral or feed mix that you use is labeled for anaplasmosis prevention, and follow label directions precisely. Ensure that animals have easy access to medication during the vector season. Keep all medicated feed, salt-mineral mixes and blocks out of direct sunlight and rain.