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.