The incubation period varies from three to four weeks. Infected animals first show a fever, which may rise to 107°F; (62°C;) in severe cases, and then jaundice and anemia set in. Pregnant cows will frequently abort. Treatment of anaplasmosis consists of antibiotic therapy and blood transfusions, administration of fluids, and rest. Protecting well animals through the routine use of insecticides or insect repellents (to control insects that carry the rickettsia) or by vaccination limits the incidence of the disease.
The organism can go through a complete lifecycle in the gut of certain species of ticks but the flies appear to be only a mechanical vector, thus, not as important in the maintaining the disease in any given area. The disease causes severe anemia and wasting in adult cattle which are infected. Young cattle and most other ruminants will not show clinical signs if infected but may serve as carriers. Since the organism "hides" from the body's immune system in red blood cells, it is difficult if not impossible for an infection to be totally cleared. As the immune response wanes, the organism again builds up and the host relapses.
In the United States, anaplasmosis is notably present in the south and west where the tick hosts Dermacentor spp. are found. Although vaccines have been developed, none are currently available in the United States. Early in the 20th century, this disease was considered one of major economic consequence in the western United States. In the 1980s and 1990s, control of ticks through new acaricides and practical treatment with prolonged-action antibiotics, notably tetracycline, has led to the point where the disease is no longer considered a major problem.
Cases of coinfection with tick-born microorganisms are being increasingly reported in the last decade , perhaps explaining the variable manifestations and clinical responses noted in some patients with tick-transmitted diseases. In such clinical settings, laboratory testing for coinfection is indicated to ensure that appropriate antimicrobial treatment is given.