Susceptibility of severe combined immuno‐deficient (SCID) mice to Trypanosoma brucei gambiense and T. b. rhodesiense

Susceptibility of severe combined immunodeficient (SCID) mice to 7 isolates of Trypanosoma brucei gambiense and 2 isolates of T. b. rhodesiense was examined in terms of their infectivity, course of parasitaemia, packed cell volume (PCV) and survival period in comparison with that of normal immunocompetent (BALB/c) mice. All isolates of T. b. gambiense and T. b. rhodesiense caused high (> 1 × 108 parasites/ml) parasitaemia in the SCID mice, the survival periods ranged from 5 to 47 days. On the other hand, 5 of 7 isolates of T. b. gambiense developed chronic infection in the BALB/c mice with sporadic but persistent parasitaemia with less than 5 × 106 parasites/ml. All the mice tested in this group survived more than 60 days after infection. In contrast, the 2 remaining isolates of T. b. gambiense and both isolates of T. b. rhodesiense showed high virulence in the BALB/c mice and killed all of them within 30 days after infection. The results demonstrate that the SCID mice, in which functional B‐ and T‐cell‐mediated immunities are congenitally lacking, are highly susceptible for ‘low‐virulence’T. b. gambiense. This makes SCID mice useful tools for the isolation of parasites from T. b. gambiense sleeping sickness patients and the propagation of large amounts of such parasites.