Anaplasmosis

• Anaplasmosis is a tickborne disease of ruminants caused by intracellular bacteria that infect red blood cells, leading to fever and anemia
• Cattle, sheep, goats, buffalo, and some wild ruminants can be infected with the erythrocytic Anaplasma
• Anaplasmosis occurs in tropical and subtropical regions worldwide, including South and Central America, the USA, southern Europe, Africa, Asia, and Australia
• Anaplasmosis in ruminants is caused by several species of bacteria of the genus Anaplasma, including Anaplasma marginale and Anaplasma centrale
• Anaplasma centrale causes less severe clinical signs than Anaplasma marginale
• Transmission of Anaplasma occurs through several hard tick species and other arthropods, as well as fomites
• After an incubation period of 7 to 60 days, A. marginale invades erythrocytes and begins cycles of replication, reticuloendothelial system removal, and reinfection of erythrocytes
• Between 10% and 90% of the entire pool of circulating erythrocytes may be infected acutely, with at least 15% needing to be infected for clinical signs to occur
• Throughout the persistently infected animal’s life, there are consistent cycles over a repeating 10- to 14-day period of increasing, followed by decreasing, numbers of infected circulating erythrocytes
• Seroconversion occurs in infected clinical and carrier cattle and may be detected as early as 9 days after infection using a commercially available competitive ELISA (cELISA) assay
• Clinical signs of anaplasmosis include fever, anemia, weakness, anorexia, constipation, yellowing of the mucous membranes, dehydration, and reduced performance
• Lesions in anaplasmosis are typical of those found in animals with anemia due to erythrophagocytosis
• Diagnosis of anaplasmosis is based on clinical signs, blood smears, and serologic testing
• Treatment of anaplasmosis involves prompt administration of tetracycline drugs and blood transfusion in severe cases
• Control of anaplasmosis includes various immunization methods and tick vector eradication or control