Isidore Hoyochi

Malaria and dengue fever are transmitted by female mosquitoes of the Anopheles and Aedes genera, respectively. These diseases are among the most prevalent

Insecticidal pressure on Anopheles gambiae sensu lato populations has contributed not only to the selection of physiological resistance mechanisms but also

Aedes mosquitoes are major vectors responsible for the transmission of arboviral diseases. This study aimed to identify the types of breeding sites colonized by Aedes mosquitoes and to assess the epidemic risk of arboviral diseases across communes in Benin. From January to November 2024, mosquito larvae were collected in nine study communes. All water-holding containers encountered were inspected for larvae and pupae. Samples of larvae and pupae were collected, pooled by breeding site type, and reared to adulthood for species identification. The frequency of different breeding site types was recorded. Epidemic risk was assessed using the House, Container and Breteau indices. Aedes aegypti (70.7%) was the most abundant species, followed by Culex quinquefasciatus (25.3%). Breeding sites were mainly artificial and included domestic containers (buckets, jars, drums, cans, cisterns, water troughs), tyres, and discarded containers (tin cans). The House, Container and Breteau indices indicated a high epidemic risk of arboviral diseases across the communes. The wide diversity of breeding sites supporting Aedes development, coupled with the high epidemic risk indices, highlights the urgent need for integrated vector control strategies, with priority given to identified high-risk areas.

Malaria is a disease transmitted by the Anopheles gambiae complex, represented mainly in Benin by the sister species An. coluzzii and An. gambiae sensu stricto. Intensive vector control interventions have selected physiological, behavioural and biochemical adaptation mechanisms in these populations of An. vectors. This study aimed to investigate the mechanism of the metabolic resistance of An. coluzzii to insecticides in two urban areas in southern Benin. Larvae and pupae of An. gambiae s.l. and were collected in the municipalities of Cotonou and Porto-Novo between May and August 2021. The World Health Organization (WHO) sensitivity tests were performed on adult An. gambiae s.l. derived from larvae and pupae. Diagnostic doses of 0.05% deltamethrin, 0.75% permethrin, and 0.1% bendiocarb were used. Species belonging to the An. gambiae complex were identified by PCR, and detoxification enzymes (oxidase, glutathione-S-transferase and esterase) were investigated in An. coluzzii. The results showed that An. gambiae s.l. developed resistance to deltamethrin, permethrin and suspected resistance to bendiocarb in the municipalities of Porto-Novo and Cotonou. In addition, the PCR results revealed that An. coluzzii was the predominant species in the municipalities of Cotonou (p < 0.0001) and Porto-Novo (p = 0.002) compared with An. gambiae. Biochemical analysis revealed significantly greater oxidase activity in An. coluzzii in the municipality of Cotonou (p < 0.0001) and low activity in Porto-Novo (p = 0.0958) compared with the susceptible An. coluzzii N’gousso reference strain. Compared with the susceptible An. coluzzii N’gousso reference strain, very high GST activity was detected in the populations of An. coluzzii of Cotonou (p < 0.0001) and Porto-Novo (p = 0.0015). Finally, significantly greater esterase activity (α- and β-esterase) was detected in Porto-Novo than in the susceptible reference strain An. coluzzii N’gousso. Low but not significant esterase activity was also observed in An. coluzzii in Cotonou (p = 0.2120). This study reveals metabolic resistance mechanisms to pyrethroids and carbamates in An. coluzzii populations in the Porto-Novo and Cotonou municipalities. This study confirms the involvement of detoxification enzymes in increased tolerance to these insecticides.

Background: Malaria, dengue and lymphatic filariasis are diseases transmitted by Anopheles, Aedes and Culex mosquitoes, respectively. These mosquitoes have evolved and adapted to environmental conditions and human lifestyles, providing them with a variety of breeding sites. This study aimed to determine the influence of the physicochemical characteristics of breeding sites on the distribution of Anopheles, Aedes and Culex mosquitoes in Benin. Methods: The collections took place from January to November 2025 and lasted 9 months. Mosquito larvae were collected from 11 municipalities in Benin. Physicochemical parameters such as pH, temperature, salinity, total dissolved solids, conductivity, dissolved oxygen and turbidity were measured in situ during larval sampling. Variations among the physicochemical parameters were assessed via Chi-square multiple comparisons of proportions and the least significant difference (LSD) test following analysis of variance (ANOVA). Correlations between physicochemical variables were analyzed via principal component analysis (PCA). Results: The results revealed that domestic containers and tires were the most common indoor and outdoor breeding sites for human dwellings, respectively. The pH levels slightly varied across the different breeding sites but generally remained nearly neutral. The temperatures were relatively consistent among the habitats, averaging approximately 30 °C. Salinity levels were close to zero at most Aedes and Anopheles breeding sites, whereas Culex larvae were commonly associated with sites with salinity values close to one. The total dissolved solids and conductivity varied considerably among the sites. Dissolved oxygen was positively correlated with the presence of Anopheles larvae. Both Aedes and Anopheles are typically found in habitats with low turbidity, whereas Culex larvae are associated with highly turbid environments, with turbidity ranging from 10 to 858 NTU. Principal component analysis revealed strong positive correlations between conductivity, salinity, and TDS; weak correlations between turbidity and temperature; and negative correlations between dissolved oxygen, conductivity, and salinity. Conclusion: This study highlights the importance of the physicochemical properties of breeding sites in the distribution of primary vector mosquito species. The prevalence of domestic containers and tires as breeding sites underscores the necessity of targeted interventions in these habitats, both indoors and outdoors of human dwellings.