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Summer Brings Insects And Anemia-Inducing Disease To Cattle

Controlling insects and using good sanitation of veterinary equipment can help prevent spread of anaplasmosis, a sometimes-fatal cattle disease that attacks red blood cells.

“Outbreaks generally occur in late summer and early fall, but it’s not too early to take steps to prevent the spread of the bacteria that causes anaplasmosis,” said Tom Troxel, associate head-Animal Science, for the University of Arkansas System Division of Agriculture. “This highly infectious disease has an incubation period of 21-45 days.”

Anaplasmosis is transmitted between animals by biting flies such as horseflies or stable flies, ticks and contaminated needles or equipment such as dehorners, castration and tattoo instruments.

“Once the red blood cells initially become infected, the organism reproduces, infecting more cells,” Troxel said. In this initial phase, infected animal shows little or no signs of illness.

“However, when the infected animal’s immune system begins to respond and attempts to attack the invader, it destroys not only the bacteria, but also the blood cells that were infected,” he said. “As a result, the signs of clinical anemia will appear.”

This disease is typically age related. Calves less than one year old usually show no symptoms of this disease and are considered mild. Cattle 12 to 24 months of age can show acute signs of the disease, but it is rarely fatal.

“However, animals that are two years and older will show acute signs of the disease, and mortality rates may be as great as 50 percent if animals are left untreated,” Troxel said.

Survivors maybe carriers
Some cattle that do survive without treatment may become carriers for the disease.

“They will serve as a reservoir and be an underlying source of infection for other susceptible cattle in the herd,” he said. “Animals in the carrier phase usually show no clinical signs and rarely become ill a second time with the disease.”

Early clinical signs include a rectal temperature of 104-107 degrees Fahrenheit, a decrease in appetite, pale mucous membranes, lethargy, a decrease in milk production and weakness. As the disease progresses, other signs may be noted such as weight loss, yellowed mucous membranes, constipation, excitation, abortion and death.

“Death is due to a large number of red blood cells being lost,” Troxel said. “This inhibits the animal’s ability to provide adequate oxygen to the tissues, and death by suffocation occurs.”  

Prevention of this disease can incorporate many factors. Insect control can be difficult, but pesticide applications to the herd may limit the number of potential vectors. Feeding chlortetracycline at the rate of 0.5 mg-per-pound of cow body weight during the vector season will help prevent transmission of Anaplasmosis. CTC may be included in medicated feed, mineral mix or feed blocks.

“It also is important to be mindful of contaminated needles or instruments,” he said. “When performing herd work, change needles often, and keep castration knives, dehorners or tattoo instruments in disinfectant between uses.”

Vaccines are also available to help with the control and prevention of anaplasmosis. Troxel recommends contacting your veterinarian for addition prevention or treatment protocols.


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