Anaplasmosis


 * This article is about the ruminant disease. For anaplasmosis in dogs, see Ehrlichiosis (canine). For anaplasmosis in humans, see Human granulocytic ehrlichiosis.

Anaplasmosis is a disease caused by a rickettsial parasite of ruminants, Anaplasma spp. The organism occurs in the erythrocytes and is transmitted by natural means through by a number of haematophagous species of ticks and flies. It can also be transmitted iatrogenically by the use of surgical, dehorning, castration, and tattoo instruments and hypodermic needles that are not disinfected between uses.

Anaplasmosis, caused by Anaplasma phagocytophilum, causes symptoms of fever, headache, and myalgia, with GI symptoms occurring in less than half of the patients and a skin rash in less than 10% of patients. It is also characterized by thrombocytopenia, leukopenia, and elevated serum transaminase levels in the majority of infected patients. The causative bacterium is transmitted to humans via ticks.

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.