Association between sodalis glossinidius and trypanosome infections in tsetse flies from the Kafue national park ecosystem in Zambia.

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Kallu, Adugna, Simegnew
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The University of Zambia
Tsetse flies are obligate hematophagous vectors of animal and human African trypanosomoses. They cyclically transmit pathogenic Trypanosoma species. Despite having a long history of chemotherapy and chemical methods of vector control, African trypanosomosis has continued causing huge economic losses. Due to their distinct reproductive biology, tsetse flies are recalcitrant to germ-line transformation. A paratransgenic approach using Sodalis glossinidius as a delivery system for trypanocidal components is currently of considerable interest to generate a trypanosome resistant tsetse fly. The aim of this study was to assess the association of S. glossinidius and trypanosome infections in a natural tsetse fly population. Tsetse flies were caught at two sites (Chunga and Ngoma) in the Kafue National Park ecosystem, Zambia. Trapped tsetse fly species and their sex were identified morphologically using a stereomicroscope. Deoxyribonucleic acid (DNA) was extracted from the whole tsetse flies and checked for the presence of S. glossinidius and trypanosome DNA by polymerase chain reaction (PCR). Chi-square statistical analysis were done to check whether there was an association between the presence of S. glossinidius and trypanosome infections. A total of 326 tsetse flies consisting of two species were trapped from Kafue National Park ecosystem, Zambia. These included Glossina morsitans that represented 82.8% (95% CI: 78.35- 86.53) and Glossina pallidipes that accounted for 17.2% (95% CI: 13.47- 21.65) of the caught tsetse flies. Out of the total tsetse fly population, the prevalence of S. glossinidius was 21.8% (95% CI: 17.64-26.57) and trypanosome infection rate was 19.3% (95% CI: 15.41-23.96). The prevalence of pathogenic trypanosome species detected in this study were 6.4% , 4.6%, 4.0%, 3.7%, 3.1% and 2.5% for T. vivax, T. simiae, T. congolense, T. godfreyi, T. simiae Tsavo, and T. b. brucei, respectively. Out of 63 trypanosome infected tsetse flies, 47.6% of the flies also carried S. glossinidius, while the remaining flies were devoid of S. glossinidius. From overall data analyzed, statistically significant association was found between tsetse flies harbouring S. glossinidius and tsetse flies infected with trypanosomes (p < 0.001). The association of individual trypanosome species with presence of S. glossinidius indicated that statistically significant associations were found between S. glossinidius and T. vivax (p = 0.006), T. simiae (p = 0.025), T. simiae Tsavo (p = 0.009), and T. godfreyi (p = 0.027), but no significant association between S. glossinidius and T. congolense (p = 0.491), and T. b. brucei (p = 0.072). This result supports the hypothesis that presence of S. glossinidius increases the susceptibility of tsetse flies to trypanosome infections and S. glossinidius could be a potential candidate to symbiont-mediated vector control in these tsetse species.
Trypanosoma. , Trypanosoma species. , Tsetse flies.