Improvement of tsetse fly salivation technique for the detection of infective metatrypanosomes: study of the impact of certain biological and non-biological factors on probing behaviour of tsetse flies

Abstract

The prohing and salivation behaviour on a warm slide of three tsetse fly species or subspecies (Glossina morsitans morsitans, Glossina palpalis gambiensis, Glossina tachinoides) was examined with respect to various parameters (species, sex, age, starvation period, trypanosome infection, quality of support). Each fly was given the opportunity to probe the warm slide (38°C) for 5 minutes (we mean by probing an attempt to touch the glass slide by the proboscis in a biting position). G. m. morsitans is by far the most efficient at probing (70.50 %) when compared with G. tachinoides (50.50 %) and G. palpalis gambiensis (45.80 %). Globally, males (61.30 %) are more active than females (52 %) and those of the morsitans group are more active than those of the palpalis group. Teneral flies probe more easily than non-teneral flies, with an increased advantage in G. m. morsitans. The starvation period increases the probing behaviour, but at 48 h, G. m. morsitans probed as much as G. palpalis gambiensis and G. tachinoides at 72 h. The males of G. m. morsitans and G. palpalis gambiensis are more precocious than females, but the inverse is observed in G. tachinoides. Infection by T. congolense (EATRO 325 strain) does not affect the probing behaviour of males of all 3 species but seems to lower that of females in the palpalis group. Addition of a drop of PSG or blood improves the probing behaviour of infected G. m. morsitans females (the only ones tested). The results are discussed in relation to biological data and knowledge of the receptor systems of tsetse flies.