Colonization of the tsetse fly midgut with commensal Enterobacter inhibits trypanosome infection establishment

Abstract

14 15 Keywords: African trypanosome, tsetse fly, Enterobacter, Sodalis, sterile insect 16 technique (SIT) 17 Abstract 18 Tsetse flies (Glossina spp.) vector pathogenic trypanosomes (Trypanosoma spp.) in 19 sub-Saharan Africa. These parasites cause human and animal African20 trypanosomiases, which are debilitating diseases that inflict an enormous socio-21 economic burden on inhabitants of endemic regions. Current disease control strategies 22 rely primarily on treating infected animals and reducing tsetse population densities.23 However, relevant programs are costly, labor intensive and difficult to sustain. As such, 24 novel strategies aimed at reducing tsetse vector competence require development.25 Herein we investigated whether an Enterobacter bacterium (Esp_Z), which confers 26 Anopheles gambiae with resistance to Plasmodium, is able to colonize tsetse and 27 induce a trypanosome refractory phenotype in the fly. Esp_Z established stable 28 infections in tsetse's gut, and exhibited no adverse effect on the survival of individuals 29 from either group. Flies with established Esp_Z infections in their gut were significantly 30 more refractory to infection with two distinct trypanosome species (T. congolense, 6% 31 infection; T. brucei, 32% infection) than were age-matched flies that did not house the 32 exogenous bacterium (T. congolense, 36% infected; T. brucei, 70% infected).33 Additionally, 52% of Esp_Z colonized tsetse survived infection with entomopathogenic 34 Serratia marcescens, compared with only 9% of their wild-type counterparts. These 35 parasite and pathogen refractory phenotypes result from the fact that Esp_Z acidifies 36 tsetse's midgut environment, which inhibits trypanosome and Serratia growth and thus 37 infection establishment. Finally, we determined that Esp_Z infection does not impact the 38 fecundity of male or female tsetse, nor the ability of male flies to compete with their wild-39 type counterparts for mates. We propose that Esp_Z could be used as one component 40 of an integrated strategy aimed at reducing the ability of tsetse to transmit pathogenic 41 trypanosomes. Author Summary44 Tsetse flies transmit pathogenic African trypanosomes, which are the causative agents 45 of socio-economically devastating human and animal African trypanosomiases. These 46 diseases are currently controlled in large part by reducing the population size of tsetse 47 vectors through the use of insecticides, traps and sterile insect technique. However, 48 logistic and monetary hurdles often preclude the prolonged application of procedures 49 necessary to maintain these control programs. Thus, novel strategies, including those 50 aimed at sustainably reducing the ability of tsetse to transmit trypanosomes, are 51 presently under development. Herein we stably colonize tsetse flies with a bacterium 52 (Enterobacter sp. Z, Esp_Z) that acidifies their midgut, thus rendering the environment 53 inhospitable to infection with two distinct, epidemiologically important trypanosome 54 strains as well as an entomopath...

Molecular detection of Sodalis glossinidius, Spiroplasma and Wolbachia endosymbionts in wild population of tsetse flies collected in Cameroon, Chad and Nigeria

“…Transmission of pathogens by vector depends on its vector competence, which can be affected by several factors, including vector endosymbionts [31]. Due to their importance, interactions between the symbionts and their hosts are being harnessed toward the development of novel approaches for vector and disease control [32][33][34].…”