Spatiotemporal changes in prevalence of Sodalis glossinidius, Spiroplasma spp. and trypanosome species in wild Glossina tachinoides from Sora-Mboum animal African trypanosomiasis focus in northern Cameroon

Sterile Insect Technique (SIT) has proven effective to reduce tsetse population density in large infected areas where animal African trypanosomosis (AAT) and human African trypanosomiasis (HAT) elimination was difficult to achieve. However, the decrease in mass production of insectary-reared tsetse and the limited but incomplete knowledge on symbiont–trypanosome interaction over time, impede large-scale use of SIT. We investigated the spatiotemporal changes in symbiont prevalence and symbiont–trypanosome interactions in wild tsetse of Sora-Mboum AAT focus in northern Cameroon, collected in 2019 and 2020, to provide insights into the mass production of refractory tsetse. Spiroplasma spp., Sodalis glossinidius and trypanosomes were screened with PCR. G. tachinoides was the most abundant Glossina species found in Sora-Mboum focus. Symbiont prevalences in G. tachinoides were higher in 2019 compared to 2020, from 67.6% to 53.5% for Spiroplasma spp. and from 28.8% to 8.1% for S. glossinidius. These symbionts were also found at higher prevalence in flies from Mouhoun HAT focus in Burkina Faso. Four trypanosome taxa (Trypanosoma congolense forest type, T. congolense savannah type, T. brucei s.l., and T. vivax) were found in Sora-Mboum focus and Mouhoun focus, though at lower prevalence in Mouhoun. The presence of Spiroplasma spp. in adult tsetse was negatively associated with that of trypanosomes. Our study highlights the potential of Spiroplasma spp. as a good paratransgenesis candidate to enhance SIT application. This symbiont is naturally found in high proportions of tsetse and could prevent factory flies from acquiring and transmitting trypanosomes during their lifespan when released for population density control.