Extrachromosomal inheritance of susceptibility to trypanosome infection in tsetse flies. II. Susceptibility of selected lines of Glossina morsitans morsitans to different stocks and species of trypanosome.

Two lines of Glossina m. morsitans, selected for susceptibility and refractoriness to infection with a single stock of Trypanosoma congolense, have now been shown to be susceptible or refractory to different stocks of T. congolense and, also, to different stocks of T. b. brucei and T. b. gambiense. The mean midgut infection rates of the susceptible line obtained in different experiments with T. congolense, T. b. brucei and T. b. gambiense were, respectively, 66%, 56% and 55%; the corresponding mature (hypopharynx or salivary gland) infection rates were 37%, 23% and 0%. The highest mature infection rates obtained in individual experiments with susceptible flies were 65% (T. congolense) and 40% (T. b. brucei). Mean T. congolense and T. b. brucei midgut infection rates obtained with the refractory line were 29% and 33% respectively, the mature infection rates being 12% and 7%, all significantly lower than the corresponding rates in the susceptible line.Development of midgut infections in susceptible flies ap...