Clinicopathological study on experimental Trypanosoma brucei infections in horses. Part 1. Development of clinically recognizable nervous symptoms in nagana-infected horses treated with subcurative doses of Antrypol and Berenil

Abstract

Studies on the pathogenesis and symptomatology of the acute and chronic forms of human sleeping sickness and those appearing in equine nagana caused by Trypanosoma brucei Plimmer & Bradford, 1899 are given. In man the initial invasion of the blood stream and lymph nodes by either T. rhodesiense Stephens & Fantham, 1910 or T. gambiense Dutton, 1902 is invariably followed by parasites entering the cerebrospinal fluid and eventually extending to the brain and producing symptoms of meningo-encephalitis. In horses the invasion of the blood stream and lymph nodes by T. brucei results in the development of a peracute, acute or chronic disease which nearly always terminates fatally without clinical evidence of an involvement of the central nervous system. Consideration of the relatively short reaction periods of 2 to 3 months in T. brucei infections when compared with those of 9 months to several years in human trypanosomiasis, suggested that prolongation of the course of nagana in horses by subcurative treatments with Antrypol and Berenil would allow the parasite sufficient time to enter the cerebrospinal fluid and then to exert its pathogenicity on the central nervous system. It was found that such treatments resulted both in the extension of the course and in the appearance of nervous symptoms in two of the five treated horses. The involvement of the central nervous system was confirmed at necropsy by a mild hydrocephalus, oedema of the brain, thickening of the meninges and the detection of T. brucei in the cerebrospinal fluid. Evidence is presented that in common with T. rhodesiense and T. gambiense, T. brucei under certain conditions exerts its invasive potential for the cerebrospinal fluid.