|Anaplasma centrale infecting the red blood cells of a cow: The arrow points to typical infected cell.|
Anaplasmosis is a disease caused by a rickettsial parasite of ruminants, Anaplasma spp. The microorganisms are Gram-negative, and infect red blood cells. They are transmitted by natural means through a number of haematophagous species of ticks. The Ixodes tick that commonly transmits Lyme disease also spreads anaplasmosis. Anaplasmosis can also be transmitted by the use of surgical, dehorning, castration, and tattoo instruments and hypodermic needles that are not disinfected between uses.
Signs and symptoms
Classic signs and symptoms of anaplasmosis include fever, a decreased number of white blood cells, platelets in the bloodstream, and abnormally elevated levels of liver enzymes. The erythema chronicum migrans rash may be seen with anaplasmosis as it is co-transmitted in 10% of Lyme disease cases.
Anemia 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.
Several species of rickettsial bacteria cause anaplasmosis in ruminants:
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.
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, A. ovis was found in reindeer populations in Mongolia. This pathogen and its associated syndrome (characterized by lethargy, fever, and pale mucous membranes) was previously observed in only wild sheep and goats in the region, and is the first observed event of A. ovis in reindeer.
In Australia, bovine anaplasmosis, caused by A. marginale, is found in only 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.
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