Detection of Wolbachia and different trypanosome species in Glossina palpalis palpalis populations from three sleeping sickness foci of southern Cameroon

Sartrien Tagueu Kanté,Trésor Melachio,Gustave Simo,Flobert Njiokou,Elvis Ofon

doi:10.1186/s13071-018-3229-2

Sartrien Tagueu Kanté, Trésor Melachio + Show 3 more

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https://doi.org/10.1186/s13071-018-3229-2

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Abstract

BackgroundAfrican trypanosomiases are caused by trypanosomes that are cyclically transmitted by tsetse. Investigations aiming to generate knowledge on the bacterial fauna of tsetse have revealed distinct symbiotic microorganisms. Furthermore, studies addressing the tripartite association between trypanosomes-tsetse-symbionts relationship have so far been contradictory. Most studies included Sodalis glossinudius and, consequently, the association involving Wolbachia is poorly understood. Understanding the vectorial competence of tsetse requires decrypting these tripartite associations. In this study, we identified Wolbachia and trypanosomes in Glossina palpalis palpalis from three human African trypanosomiasis (HAT) foci in southern Cameroon.MethodsTsetse flies were captured with pyramidal traps in the Bipindi, Campo and Fontem HAT foci. After morphological identification, DNA was extracted from whole tsetse flies and Wolbachia and trypanosomes were identified by PCR using different trypanosome-specific primers and two Wolbachia-specific primers (Wolbachia surface protein and 16S rRNA genes). Statistical analyses were performed to compare the trypanosome and Wolbachia infection rates between villages and different foci and to look for an association between these microorganisms.ResultsFrom a total of 2122 tsetse flies, 790 G. p. palpalis were analyzed. About 25.32% of flies hosted Wolbachia and 31.84% of non-teneral flies were infected by at least one trypanosome species. There was no significant difference between the global Wolbachia prevalence revealed by the two markers while some differences were observed between HAT foci. From 248 G. p. palpalis with trypanosome infections, 62.90% were with T. vivax, 34.68% with T. congolense forest, 16.13% with T. brucei (s.l.) and 2.42% with T. congolense savannah. Of all trypanosome-infected flies, 29.84% hosted Wolbachia and no association was observed between Wolbachia and trypanosome co-infections.ConclusionsThis study revealed differences in the prevalence of Wolbachia and trypanosomes in G. p. palpalis according to HAT foci. The use of only one marker has underestimated the prevalence of Wolbachia, thus more markers in subsequent studies may improve its detection. The presence of Wolbachia seems to have no impact on the establishment of trypanosomes in G. p. palpalis. The tripartite association between tsetse, Wolbachia and trypanosomes varies according to studied areas. Studies aiming to evaluate the genetic polymorphism of Wolbachia and its density in tsetse flies could help to better understand this association.

Highlights

African trypanosomiases are caused by trypanosomes that are cyclically transmitted by tsetse
Two subspecies of African trypanosomes are pathogenic for humans: Trypanosoma brucei rhodesiense that causes the acute form of human African trypanosomiasis (HAT) in eastern and southern Africa, and T. b. gambiense which is responsible for the chronic form of HAT in western and central Africa [1, 2]
Entomological surveys From the 197 traps used in this study, a total of 2122 tsetse flies were collected during the four entomological surveys: 1216 (57.3%) tsetse flies were caught in the Bipindi HAT focus, 632 (29.78%) in the Campo focus and 274 (12.91%) in the Fontem focus

Summary

Introduction

African trypanosomiases are caused by trypanosomes that are cyclically transmitted by tsetse. Studies addressing the tripartite association between trypanosomes-tsetse-symbionts relationship have so far been contradictory. We identified Wolbachia and trypanosomes in Glossina palpalis palpalis from three human African trypanosomiasis (HAT) foci in southern Cameroon. With a certain number of requirements linked to environmental factors such as the climate, the vegetation, the type of soil, the presence of domestic and/or wild fauna, and the effects of human activity, the distribution of tsetse flies is discontinuous across 37 sub-Saharan countries. Tsetse flies are the cyclical vector of African trypanosomes that cause human and animal African trypanosomiases. Two subspecies of African trypanosomes are pathogenic for humans: Trypanosoma brucei rhodesiense that causes the acute form of human African trypanosomiasis (HAT) in eastern and southern Africa, and T. b. Efforts undertaken on HAT control have brought the disease under control and led to its inclusion into the WHO “roadmap for elimination of neglected tropical diseases” with a target set to eliminate HAT as a public health problem by 2020 [1]

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