Experimental comparison of survival and trypanosome infection rate between two tsetse fly species under different feeding conditions

Abstract

The survival and infection rate of tsetse flies are important parameter for the success of sterile insect technique (SIT) and in vector monitoring program that allows a more precise evaluation of the risk of being infected in a particular region. The objectives of this longitudinal experimental study was to compare the survival and trypanosome infection rate of two tsetse fly species; G. pallidipes and G. f. fuscipes under experimentally trypanosomes infected calves (in-vivo) and using irradiated bovine blood (in-vitro) feeding conditions. A total of 900 (450 G. pallidipes and 450 G. f. fuscipes) male and female flies were used for this experiment. The flies were kept in a cage with a density of 25 flies per cage and divided into 9 groups each with 4 cages which fed on nine experimentally infected calves and irradiated bovine blood using a silicon membrane. The infection rate evaluation of the two species were carried out using warm slide technique through microscopy examination of the saliva of each survived flies. Accordingly, the survival rate, mean percentage of surviving flies, under calves feeding were 85.8% and 76.2% for G. pallidipes and G. f. fuscipes, respectively (p=0.001). Higher survival rate of females (84%) than males (77.9%) were observed which had statistically significant difference (p=0.019). Under in-vitro feeding, 88.4% and 92.2% survival percentage of G. pallidipes and G. f. fuscipes were observed, respectively (p=0.076). The survival rate of flies maintained under in-vitro feeding was higher than flies maintained under calves (in-vivo) feeding. The overall trypanosomes infection rate in the two species were 19.6% and 8.3% for G. pallidipes and G. f. fuscipes, respectively (p=0.002). There were significant difference in infection rate between females and males in both species in which females had higher infection rate (p