Path of Science: International Electronic Scientific Journal

Accurate identification of sibling species within the Anopheles gambiae complex is important for understanding malaria-vector ecology and for informing vector surveillance and control. Morphological identification alone cannot reliably distinguish members of this complex, so molecular approaches are necessary for species-level characterisation.

Adult mosquitoes were collected by pyrethrum spray catch between 06:00 and 08:00 from household compounds in four communities—Gbuwhen, Lankan, Maiganga, and Seri—in Nasarawa and Plateau States, North-Central Nigeria, during seasonal collections in May, July, and September between 2000 and 2023. A total of 18,157 mosquitoes were collected, of which 1,152 specimens identified morphologically as members of the An. gambiae complex were selected for molecular identification. We extracted genomic DNA from individual mosquitoes and amplified it by multiplex PCR using intentional-mismatch primers targeting diagnostic ribosomal DNA regions. Species composition was summarised by community and described using the Shannon and Simpson diversity indices; differences among communities were evaluated using Fisher’s exact test, the chi-square test and a test of proportions.

Molecular analysis identified two members of the An. gambiae complex: Anopheles gambiae sensu stricto and Anopheles coluzzii. An. gambiae s.s. was overwhelmingly predominant, accounting for more than 99% of identified specimens, whereas An. coluzzii occurred at very low frequency (0.8% or less) and was recovered in only two of the four communities. No statistically significant difference in species composition was detected among communities (Fisher’s exact test, p = 0.23; χ² = 4.30, df = 3, p = 0.23). Shannon and Simpson indices were correspondingly low (Shannon 0–0.045; Simpson 0–0.015), consistent with strong numerical dominance by An. gambiae s.s.

In the study communities, one member of the An. gambiae complex strongly predominates over the other, with An. coluzzii present only at trace frequency. Because An. coluzzii was rare, the analysis had limited power to detect moderate differences among communities, and the absence of a significant difference should not be read as evidence that composition is uniform. The findings provide baseline information for entomological surveillance; continued molecular monitoring is required to establish whether species composition varies across locations or shifts over time.

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