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

Abstract

Background Tsetse flies are cyclical vectors of African trypanosomiasis. They have established symbiotic associations with different bacteria, which influence certain aspects of their physiology. The vector competence of tsetse flies for different trypanosome species is highly variable and is suggested to be affected by various factors, amongst which are bacterial endosymbionts. Symbiotic interactions may provide an avenue for the disease control. The current study provided the prevalence of 3 tsetse symbionts in Glossina species from Cameroon, Chad and Nigeria. Results Tsetse flies were collected from five different locations and dissected. DNA was extracted and polymerase chain reaction PCR was used to detect the presence of Sodalis glossinidius , Spiroplasma sp and Wolbachia using specific primers. A total of 848 tsetse samples were analysed: Glossina morsitans submorsitans (47.52%), Glossina palpalis palpalis (37.26%), Glossina fuscipes fuscipes (9.08%) and Glossina tachinoides (6.13%). Only 95 (11.20%) were infected with at least one of the 3 symbionts. Among the infected, 6 (6.31%) were carrying mixed infection ( Wolbachia and Spiroplasma ). The overall symbiont prevalence was 0.88%, 3.66% and 11.00% respectively, for Sodalis , Spiroplasma and Wolbachia . Prevalence varied between countries and tsetse species. No Spiroplasma was detected in samples from Cameroon and no Sodalis was found in samples from Nigeria. Conclusion The present study revealed for the first time, the presence of infection by Spiroplasma in tsetse in Chad and Nigeria. These findings provide useful information to the repertoire of bacterial flora of tsetse flies and incite to more investigations to understand their implication in the vector competence of tsetse flies.

Figure 1. Phylogenetic tree of detected Sodalis glossinidius’ hemolysinpartial gene and its closed relatives.

The evolutionary history conducted in MEGA X, was inferred by using the Maximum Likelihood method and Hasegawa-Kishino-Yano model. This analysis involved 10 nucleotide sequences and a total of 596 positions in the final dataset. Our isolates are marked by a black circle. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches.

Figure 2. Phylogenetic tree of detected Spiroplasma’s 16S rRNA partial gene and its closed relatives.

The evolutionary history conducted in MEGA X, was inferred by using the Maximum Likelihood method and Kimura 2-parameter model. This analysis involved 20 nucleotide sequences and a total of 383 positions in the final dataset. Our isolates are marked by a black circle. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches.

Figure 3. Phylogenetic tree of detected Wolbachia’s partial 16S rRNA gene and its closed relatives.

The evolutionary history conducted in MEGA X, was inferred by using the Maximum Likelihood method and Kimura 2-parameter model. A discrete Gamma distribution was used to model evolutionary rate differences among sites. This analysis involved 18 nucleotide sequences and a total of 377 positions in the final dataset. Our isolates are marked by a black circle. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches.

Figure 4. Study area.

Tsetse flies were collected in Cameroon (Dodeo), in Chad (Maro and Lake Iro) and in Nigeria (Yankari Game reserve and in Ija-Gwari).