Studies on the susceptibility of the Orma and Galana Boran cattle to trypanosome infection

Abstract

Genetic resistance to trypanosomiasis in cattle is a trait generally ascribed only to the Bos taurus breeds indigenous to West Africa, namely, the N'Dama and West African shorthorn. Differences in susceptibility to trypanosomiasis in Bos indicus breeds have not been critically evaluated. However, reports have indicated variations in their susceptibility. For instance a type of Zebu in Sudan and another around the shores of Lake Victoria are believed to have reduced susceptibility to trypanosomiasis. Field studies at a ranch in the coastal region of Kenya (Galana ranch) have suggested that the Orma Boran (Zebu) cattle from the Tana River area appear to be more resistant to trypanosomiasis than the Galana Boran. In order to verify the latter observation, studies were conducted under laboratory conditions. Groups of Galana and Orma Boran cattle were purchased from the ranch and kept in a fly-free accommodation at Kenya Trypanosomiasis Research Institute (KETRI). The susceptibility of the two Boran types to trypanosomiasis was compared on the basis of the severity of clinical responses, intensity of parasitaemia, severity of anaemia, ability to gain weight and trypanocidal drug requirements. Four groups of animals were used in the study. The first group (Experiment I) consisting of 12 Galana and 12 Orma steers, was inoculated intravenously with 1x10^ organisms of L. congolense (IL 1180). The second group (Experiment II) comprising ten Galana and ten steers of each type was fed upon by tsetse infected with the same stock of T. congolense. The third group (Experiment III) consisting of 12 Galana and ten Orma was injected with lxl0^ parasites of T. vivax (stock K2388). The fourth group (Experiment (xvi i i ) IV) comprising ten steers of each type was fed upon by tsetse infected with L_ vivax (stock K2589). The results showed that while most Galana animals experienced febrile episodes, elevated heart rates and increased respiratory rates, few Orma experienced these clinical signs. Galana steers lost weight, became weak and were generally .in poor condition. In contrast, the Orma steers gained weight throughout the study period....