April 2013 Articles

Archives by Months

Anaplasmosis

Anaplasmosis Dr. Tom Troxel, Professor, University of Arkansas
Anaplasmosis is an infectious disease in cattle that affects red blood cells. It is transmitted from animal to animal by biting flies (horsefly, stable fly), ticks and contaminated needles or surgical instruments (dehorners, castration instruments, tattoo instruments). This disease is typically age related. Calves less than one year of age 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. Some cattle that do survive without treatment may become carrier animals for this disease. They will serve as a reservoir and be an underlying source of infection for other susceptible cattle in the herd. Animals in the carrier phase usually show no clinical signs and rarely become ill a second time with the disease. Outbreaks generally occur in late summer and early fall. The incubation period is from 21 to 45 days, with an average length of 30 days. Once the red blood cells initially become infected, the organism replicates itself in order to infect more red blood cells. During this period, the infected animal shows little or no signs of illness. At some point, the infected animal’s immune system begins to respond and attempts to attack the invader. When this occurs, the immune system destroys the pathogen, but also destroys the infected red blood cells. As a result, the signs of clinical anemia will appear. Early clinical signs include a rectal temperature of 104°F to 107°F, 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. This inhibits the animal’s ability to provide adequate oxygen to the tissues, and death occurs due to anoxia (suffocation). Prevention 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 (CTC) 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. 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. Contact your veterinarian for additional prevention or treatment protocols.