Pathogenesis of Trypanosoma equiperdum in rabbits

Seventeen rabbits experimentally infected with Trypanosoma equiperdum were examined for lesions at different times during a 5-month period. A chancroid developed at the inoculation site in the skin, and later, similar lesions appeared in skin of the ears, eyelids, and nose. The inflammatory reaction was primarily granulomatous, and viable trypanosomes were present in all skin lesions. The rabbits had reticuloendothelial hyperplasia of spleen and lymph nodes. In 3 rabbits, there was amyloid deposition in splenic lymph nodules and renal glomeruli. Amyloid had typical fibrillar appearance by electron microscopy (EM) and was reactive for immunoglobulin M (IgM) and immunoglobulin G (IgG) with fluorescent antibody (FA). With time, there was lessening capability of T equiperdum to agglutinate in antiserums of infected rabbits, suggesting that antigenic variation occurred during infection. The serum concentrations of IgM and IgG increased significantly in the infected rabbits and then remained elevated or they decreased, though fluctuating widely. Three of 5 infected rabbits demonstrated depressed antibody response to injected ovine erythrocytes.