Human and animal tsetse-transmitted trypanosomiases are important
diseases affecting people and livestock in extensive areas of sub-Saharan Africa. Human African trypanosomiasis is caused by infections with Trypanosoma brucei gambiense or T. b. rhodesiense. Infections with T. b. gambiense usually give rise to a chronic form of human sleeping sickness in West and Central Africa that may persist for several years, whereas T. b. rhodesiense usually causes an acute infection in East Africa (1). Nevertheless, a diversity of clinical evolutions from asymptomatic to acute forms has been described in T. b. gambiense infections. Similarly, in T. b. rhodesiense, the disease has a rather chronic character in southern countries such as Malawi and Zambia (1) but can also present an acute profile with rapid progression see more to the late stage as in Uganda (2). Trypanosoma vivax is a pathogen of livestock in Africa and in South America. It is transmitted cyclically by tsetse flies and mechanically by biting flies. Differences in virulence are recognized between East and West
African T. vivax strains, the West African strains being generally regarded as more pathogenic to cattle (3). Nevertheless, there are also reports of a severe haemorrhagic disease caused by T. vivax in East Africa (4). In South America, most T. vivax infections are chronic and asymptomatic, with rare
outbreaks of severe disease (5). The salivarian trypanosomes belonging to the subgenus Nannomonas (T. congolense and T. simiae) are major pathogens of livestock in sub-Saharan GSK2126458 cell line Africa. Contrary to the T. brucei group, T. congolense has been much less studied. Currently, two major clades are distinguished within the Nannomonas subgenus with one containing the T. congolense: Savannah, Forest and Kilifi subgroups and the other containing T. simiae, T. godfreyi and T. simiae Tsavo (6). Limited experiments, comparing the virulence of one strain of each subgroup in mice and cattle, have shown differences between the subgroups with the T. congolense strain of the Savannah subgroup being the most virulent (7,8). However, experiments conducted by Masumu et al. (9) have shown substantial stiripentol variations in the virulence of T. congolense strain belonging to the Savannah subgroup. These findings were based on T. congolense stains isolated from susceptible livestock species (i.e. the domestic transmission cycle) and may not represent the natural trypanosome population as it is present in trypanotolerant wildlife (i.e. the sylvatic transmission cycle). This paper reviews the virulence profiles of T. congolense Savannah subgroup strains isolated from livestock and compares their virulence with the virulence of strains circulating in wildlife.