Experimental Trypanosoma brucei brucei infection in Holstein and white Bororo zebu cattle

Abstract

Holstein (n = 6) and white Bororo zebu cattle (n = 10) were experimentally infected with AnTat 1.1, an antigenic variant of Trypanosoma brucei brucei. Clinical signs, packed cell volume (PCV), parasitaemia, humoral immune response and haemolytic complement were monitored to study the clinical evolution and the degree of susceptibility of both breeds to T. b. brucei trypanosomosis. Animals of both breeds were highly susceptible to the infection. Holstein developed an acute disease, lethal within a few weeks, whereas white Bororo zebus developed a chronic disease with progressive inanition and death after a few months. The drop in PCV 20 days post infection was 1.2 ± 0.7 in zebu and 11.2 ± 3.6 in Holstein, indicating that zebus resisted the anaemia better than Holstein. Animals from both breeds remained parasitaemic till the terminal phase of the disease. Large quantities of AnTat 1.1 specific trypanolytic antibodies were produced during the infection, but titres were not correlated with the level of resistance. In both breeds the infection induced persistent hypocomplementaemia. The lowest complement level was 692 ± 232 units HC50/ml on day 14 post infection in Holstein (representing 42% of the initial level at day 0) and 846 ± 140 units HC50/ml on day 84 post infection in zebus (representing 79% of the initial level). The present study indicates that the responses of white Bororo zebu and Holstein cattle are quite different from those previously observed in Lagune and Borgou cattle submitted to a similar experimental infection protocol. Individual variations are important in all breeds studied.