The Development of West African Strains ofTrypanosoma gambienseinGlossina tachinoidesunder Normal Laboratory Conditions, and at Raised Temperatures

Abstract

1. An account is given of the development of strains ofTrypanosom gambienseinGlossina tachinoides.Complete development with infection of salivary glands and hypopharynx occupies from 12 to 40 days and upwards, according to the strain of trypanosome used and the temperature conditions during development.2. It is shown that the first or intestinal phase of development is passed within the extra-peritrophic space and that the lumen or intra-peritrophic space of the gut is not involved.3. The importance of the proventricular infection as an index of maturing infections is stressed, and it is shown that filamentar crithidia are always present in this organ in the later stages of infection when infection of salivary glands is taking place. It has been proved that these filamentar crithidia may constitute up to 20 per cent. of flagellates in the proventriculus and are partly responsible for the further migration to the salivary glands.4. An account is given of the infectivity toG. tachinoidesof twenty-six strains ofT. gambiensefrom epidemic and endemic sleeping sickness areas in Northern Nigeria. None of the twenty-six was proved to be non-transmissible and twenty-five of the strains gave Total Infectivity Rates in the tsetse of from 0·9–10·5, the Cyclical Developmental Rates ranging from 0·6–9·8.5. No evidence has been obtained that strains ofT. gambiensefrom chronic cases of human trypanosomiasis in endemic areas are less transmissible by tsetse than strains originating in epidemic areas.6. An account is given of experiments in whichG. tachinoidesinfected withT. gambiensewere exposed to 37° C. for varying lengths of time. The effect of high temperature during the infecting period is seen in a marked and constant increase in the proportion of tsetse infected. In the case of one strain a total infection rate of 77·8 per cent. was obtained with true cyclical development in 73·5 per cent. of the tsetse used.7. It is suggested that the temperatures at which experimental tsetse are infected in the laboratory withT. gambienseare excessively low, and an investigation is to be made into the optimum climatic conditions for development of the trypanosome in the fly with a parallel attempt to correlate this with the climatic conditions under which wild tsetse become infected in nature.