Diagnosis of Anaplasmosis in Formalin-Fixed Tissue Using the Wolbach's Giemsa Stain

Abstract

Bovine anaplasmosis is an economically significant disease that is widespread throughout the world and enzootic in 40 of the 50 states of the USA. 2 The causative agent, Anaplasma marginale, can be transmitted from infected blood by arthropod and mechanical vectors. Cattle of all ages can be infected, but severe clinical signs and death are common only in mature cattle. Clinical disease is due to anemia resulting from the intracellular destruction of parasitized erythrocytes by phagocytes. In fatal cases severe anemia, icterus, and splenomegaly are typical. Histologically, centrilobular hypoxic hepatic necrosis and splenic hemosiderosis related to erythrocyte destruction are commonly present. Diagnosis is established by identification of anaplasma bodies in the margins of erythrocytes using Giemsa or Wright-Giemsa stains or fluorescent antibody examination of blood smears or tissue impressions.’ Field necropsy specimens submitted to the California Veterinary Diagnostic Laboratory occasionally include samples from cattle that have a clinical history and histologic lesions of hypoxic liver damage or splenic hemosiderosis suggestive