Abstract

Anaplasmosis is a disease caused by a rickettsial parasite of ruminants, "Anaplasma" spp. The microorganism is gram-negative, and infects red blood cells. It is transmitted by natural means through a number of haematophagous species of ticks. Anaplasmosis can also be transmitted by the use of surgical, dehorning, castration, and tattoo instruments and hypodermic needles that are not disinfected between uses.

Causes

Several species of rickettsia bacteria cause anaplasmosis in ruminants:

- Cattle:

- "Anaplasma marginale" - found worldwide.

- "Anaplasma centrale" - found mainly in South America, Africa and the Middle East.

- Sheep and goats:

- "Anaplasma ovis" - found worldwide.

Signs and symptoms

Anaemia may be severe and result in cardiovascular changes such as an increase in heart rate. Blood in the urine may occur due to the lysis of red blood cells. General systemic signs such as diarrhea, anorexia and weight loss may also be present. A blood smear stained with Giemsa should be observed for identification of infected red blood cells and will allow definitive diagnosis.

Prevention

Vaccines against anaplasmosis are available. Carrier animals should be eliminated from flocks. Tick control may also be useful although it can be difficult to implement.

Treatment

Treatment usually involves a prescription of doxycycline (a normal dose would be 100 mg every 12 hours for adults) or a similar class of antibiotics. Oxytetracycline and imidocarb have also been shown to be effective. Supportive therapy such as blood products and fluids may be necessary.

Epidemiology

In the United States, anaplasmosis is notably present in the south and west where the tick hosts "Ixodes" spp. are found. It is also a seemingly increasing antibody in humans in Europe. 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.

In 2005, "Anaplasma ovis" was found in reindeer populations in Mongolia. This pathogen and its associated syndrome (characterized by lethargy, fever and pale mucous membranes) was previously only observed in wild sheep and goats in the region, and is the first observed event of "A. ovis" in reindeer.

In Australia, bovine anaplasmosis, caused by "Anaplasma marginale", is only found in the northern and eastern parts of Australia where the cattle tick is present. It was probably introduced as early as 1829 by cattle from Indonesia infested with the cattle tick "Boophilus microplus".

The veterinarian George P. Broussard of New Iberia, Louisiana, conducted important research anaplasmosis and brucellosis.