Abstract
Glossina sp. the tsetse fly that transmits trypanosomes causing the Human or the Animal African Trypanosomiasis (HAT or AAT) can harbor symbiotic bacteria that are known to play a crucial role in the fly's vector competence. We hypothesized that other bacteria could be present, and that some of them could also influence the fly's vector competence. In this context the objectives of our work were: (a) to characterize the bacteria that compose the G. palpalis palpalis midgut bacteriome, (b) to evidence possible bacterial community differences between trypanosome-infected and non-infected fly individuals from a given AAT and HAT focus or from different foci using barcoded Illumina sequencing of the hypervariable V3-V4 region of the 16S rRNA gene. Forty G. p. palpalis flies, either infected by Trypanosoma congolense or uninfected were sampled from three trypanosomiasis foci in Cameroon. A total of 143 OTUs were detected in the midgut samples. Most taxa were identified at the genus level, nearly 50% at the species level; they belonged to 83 genera principally within the phyla Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria. Prominent representatives included Wigglesworthia (the fly's obligate symbiont), Serratia, and Enterobacter hormaechei. Wolbachia was identified for the first time in G. p. palpalis. The average number of bacterial species per tsetse sample was not significantly different regarding the fly infection status, and the hierarchical analysis based on the differences in bacterial community structure did not provide a clear clustering between infected and non-infected flies. Finally, the most important result was the evidence of the overall very large diversity of intestinal bacteria which, except for Wigglesworthia, were unevenly distributed over the sampled flies regardless of their geographic origin and their trypanosome infection status.
Highlights
Animal African Trypanosomiasis (AAT), or Nagana, is primarily caused by Trypanosoma brucei brucei (Tbb), Trypanosoma vivax, and Trypanosoma congolense, which are transmitted to their mammalian hosts by tsetse flies belonging to the species Glossina palpalis and Glossina morsitans
The chronic form of Human African Trypanosomiasis (HAT) is caused by Trypanosoma brucei gambiense (Tbg), whereas Trypanosoma brucei rhodesiense (Tbr) causes the acute form; the two forms are transmitted to humans by G. palpalis and G. morsitans, respectively
The main objective of this study was to characterize the bacterial communities inhabiting the midgut of field-collected tsetse flies from sleeping sickness foci in Cameroon using deep sequencing
Summary
Animal African Trypanosomiasis (AAT), or Nagana, is primarily caused by Trypanosoma brucei brucei (Tbb), Trypanosoma vivax, and Trypanosoma congolense, which are transmitted to their mammalian hosts by tsetse flies belonging to the species Glossina palpalis and Glossina morsitans This disease is responsible for significant economic losses in areas where cattle are exposed to parasites (Shaw et al, 2013). The emergence of drug-resistant trypanosomes was recently reported (Baker et al, 2013) These factors are pertinent, since epidemiological modeling of the impact of global change on HAT expansion predicts that 46–70 million more people will be at risk by 2090 (Moore et al, 2012). In this context, identifying the factors involved in fly vector competence (as well as understanding how they work) may open new perspectives
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