Cerebral trypanosomiasis in cattle with mixed Trypanosoma congolense and T. brucei brucei infections

Six Boran steers were infected simultaneously with Trypanosoma congolense and T. brucei brucei while another group of 3 was inoculated with T. b. brucei one year after infection with T. congolense. Three further steers were infected with T. b. brucei alone. Whereas, the six animals which received simultaneous infections developed clinical signs of cerebral trypanosomiasis as evidenced by depression, ataxia and occasional circling, those infected with T. b. brucei alone did not. At necropsy, 4 out of the 6 simultaneously infected animals had a mild to severe disseminated non-suppurative meningoencephalitis. Trypanosoma b. brucei was isolated from the cerebrospinal fluid (CSF) of three out of the four animals with histological lesions. Two of the cattle superinfected with T. b. brucei one year after infection with T. congolense also developed both clinical and histological evidence of cerebral trypanosomiasis. Trypanosoma congolense was isolated from the CSF of one of these 2 animals. Specific antibodies to the variable surface glycoproteins (VSGs) of the infecting T. b. brucei and T. congolense clones were found in the CSF of the 8 animals that developed cerebral trypanosomiasis. In these animals however, there was neither temporal nor quantitative correlation between VSG-specific antibodies in serum and in CSF, implying a de novo synthesis of antibodies to the infecting trypanosomes in the CSF.