Department Of Zoology

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    Dr
    (2025) Abiodun Obembe, Fatima Yahaya, Adedayo Oduola, Jasini Wahedi, Samson Awolola
    ABSTRACT Emerging adult Anopheles and Culex mosquitoes migrate to human dwellings, at great risks of insecticide exposure, in search of bloodmeal. Countries like Nigeria, targeting this joint mosquito host-seeking behaviour have launched Malaria-Lymphatic Filariasis (Malaria-LF) co-intervention plans using synergistic insecticide-based control tools. However, insecticide resistance currently threatens mosquito vector control. This study investigated separate and combined pyrethroid insecticide exposure response of Anopheles gambiae sensu lato (s.l.) and Culex pipiens complex mosquitoes collected from two mixed breeding sites in Nigeria. Adult Anopheles and Culex mosquitoes reared from larval collections were exposed in separate and joint insecticide susceptibility tests to permethrin 0.75%, deltamethrin 0.05% and alphacypermethrin (0.05%) using World Health Organization (WHO) kits. The mosquitoes were identified morphologically. Time to mosquito knockdown, percentage knockdown, and mortality were monitored. The results for the different mosquito and exposure types were compared. Both mosquitoes were resistant to all pyrethroid insecticides tested. Significantly higher Anopheles knockdown was recorded compared to Culex for the joint (Anopheles 79-89% vs Culex 44-50%, P ≤ 0.011) and separate (Anopheles 67-88% vs Culex 46-47%, P < 0.048) exposures respectively. Time to 95% Anopheles and Culex mosquito knock down were shorter during separate (2200.9 mins) than in joint (4513.9 mins) exposures. Faster Anopheles knockdown (kdt50 18.7 - 68.8 mins) were recorded compared to Culex (kdt50 22.1 - 98.8 mins). Higher but not significantly different (P ≥ 0.083) mosquito mortalities were recorded from separate than in joint Anopheles and Culex exposures. There were no significant (P ≥ 0.072) differences between Anopheles 43-77% and Culex 41-72% mortalities for separate and joint exposures. The speed of action and morbidity effects of the pyrethroid insecticides tested were lower during joint than in the separate mosquito exposures. Taken together, reduced pyrethroid speed of action and morbidity along with multiple mosquito resistance noted could threaten insecticide user-acceptability, performance perception and Malaria-LF co-intervention in the field.
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    Dr
    (MDPI, 2025) Lamine M. Moustapha; Muhammad M. Mukhtar; Abdoul-Nasser H. Sanda; Shuaibu Adamu; Yusuf Y. Aliyu; Hadizat K. Einoi; Maryam U. Maigari; Peter C. Okeke; David E. Nwele; Abiodun Obembe; Udoka C. Nwangwu; Jeremy K. Herren; Sulaiman S. Ibrahim
    Abstract Microsporidia MB (MB), a promising biological control agent, suppresses Plasmodium falciparum transmission in Anopheles mosquitoes. This study examined the spatial distribution of MB infection in natural populations of An. gambiae s.l. mosquitoes collected in Nigeria and Niger Republic, and its association with insecticide susceptibility in the mosquitoes. Microsporidia MB has wide geographic distribution across Nigeria and Niger Republic. The overall prevalence of MB in F0 mosquitoes was 12.25% (95% CI: 7.76–16.75%); 25 mosquitoes out of 204 were positive. Geographic variation was observed, with a higher prevalence (5/15 mosquitoes) in Ebonyi State (33.33%, CI: 9.48–57.19%, Fisher’s exact test, p = 0.008). Infection rates were higher in An. coluzzii mosquitoes (21/133 mosquitoes), estimated at 15.79% (CI: 9.59–21.99%) compared to An. gambiae s.s. mosquitoes (4/71), with approximately 5.63% (CI: 0.27–11.00%, χ 2 = 4.44; df = 1, p = 0.035). Resistant mosquitoes had a significantly higher prevalence of MB infection than susceptible mosquitos at 28.57% (CI: 16.74–40.40%) with an odds ratio of 3.33 (CI: 1.23–9.03, p = 0.017). These findings suggests that MB can be exploited as an alternative for vector control in Nigeria and Niger, but its possible association with pyrethroid resistance suggests that it should be taken into account as a potential confounder when designing insecticide resistance management strategies
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    Acaricidal Efficacy of Cassia sieberiana DC (Caesalpinaceae) Stem Bark Aqueous Extract on Hyalomma KOCH, 1844 (Acari: Ixodidae) Reproductive Stages
    (Arid Zone Journal of Basic and Applied Research, 2025-02) Abdullahi A. Biu; Maimunatu A. Abdulkadir; Saidu I.Ngulde; ThankGod E. Onyiche; Umar A. Maina; Raliat Aliyu; Aliyu M. Danzaria
    One of the most significant challenges facing tick control through chemical acaricides is resistance and environmental pollution, encouraging the need for natural plant products that are less toxic and environment friendly. This study was conducted to determine the acaricidal efficacy of Cassia sieberiana stem bark aqueous extract on Hyalomma species using immersion testing for egg-hatch inhibition and adult mortality. Both tests used ascending extract concentrations of 5%, 10%, 15% and 20%, at durations of 1, 2, 3, 4, 5, 6, 7 and 8 hours. Egg-hatch inhibition peaked at 5% concentration at 8hrs, 10% and 15% at 7 and 8hrs and 20% at 5, 6, 7 and 8hrs while adult mortality was highest at 20% concentration. There was a positive correlation between graded extract concentration, immersion period, egg-hatch inhibition and adult mortality. The LC50 values for adult mortality and egg hatch inhibition were 13.1 mg/mL and 13.7 mg/mL and coefficient of determination were y = 3.7x +1.5 and y = 3.062 + 8.12 respectively. Both LC50 values were almost similar indicating a strong association between extract concentration and acaricidal activity in vitro.
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    Impact of climate change on the spatial distribution of endemic legume species of the Guineo-Congolian forest, Africa
    (2021-03) Oyebanji, O. O., Salako, G., Nneji, L. M., Oladipo, S. O., Bolarinwa, K. A., Chukwuma, E. C., Ayoola, A. O., Olagunju, T. E., Ighodalo, D. J., & Nnej