Impact of Environmental Variables on the Seasonal Dynamics and Relative Abundance of Endosymbionts in Glossina Species in Northern Nigeria

Abstract This study explores how environmental factors influence the seasonal patterns and endosymbiont abundance in Glossina species across four ecological zones in northern Nigeria. Tsetse flies—the vectors of African trypanosomiasis—host both obligate and facultative endosymbionts, including Wigglesworthia glossinidia, Sodalis glossinidius , and Wolbachia pipientis , which affect their physiology and vector capacity. Over two years, 7,632 tsetse flies were collected and examined for species distribution, symbiont prevalence, and local climate variables (temperature, humidity, and vegetation index). Glossina tachinoides was most prevalent (55.78%), followed by G. morsitans submorsitans (29.36%) and G. palpalis palpalis (14.86%), each showing site-specific distribution. Endosymbiont prevalence rose markedly during the wet season (e.g., Yankari: 73.41% to 94.83%, p < 0.0001), especially for Sodalis , which declined under dry conditions. Strong negative correlations with temperature (r = –0.99, p = 0.0001) and positive correlations with humidity (r = +0.99, p = 0.0005) were observed. These patterns reflect the vulnerability of tsetse-symbiont systems to climate stress and underscore challenges for control strategies. Broad-area methods may suit G. tachinoides, while targeted trapping is more suitable for G. palpalis . The resilience of Wolbachia suggests its utility for paratransgenic control. The study emphasizes the importance of integrated, climate-aware surveillance and intervention strategies to mitigate trypanosomiasis risk. Author Summary Tsetse flies transmit African trypanosomiasis, a disease affecting livestock and rural livelihoods in sub-Saharan Africa. These flies harbor bacterial endosymbionts that influence their biology and vector competence. This study investigated how seasonal changes in temperature, humidity, and vegetation affect the abundance of tsetse flies and their symbionts in northern Nigeria. We found that certain symbionts, especially Sodalis glossinidius , decline sharply during hot-dry periods, while Wolbachia remains stable. Our findings highlight the need for adaptive, climate-informed vector control strategies and provide insights for integrating microbial monitoring into trypanosomiasis surveillance systems.