A previously unreported potential malaria vector in a dry ecology of Kenya

Abstract

Background: In Kenya, malaria remains a major public health menace equally affecting the semi-arid to arid ecologies. However, entomologic knowledge of malaria vectors in such areas remains poor.

Methods: Morphologically-identified wild-caught Anopheles funestus (s.l.) specimens trapped outdoors from the semi-arid to arid area of Kacheliba, West Pokot County, Kenya, were analysed by PCR and sequencing for species identification, malaria parasite infection and host blood-meal sources.

Results: Three hundred and thirty specimens were analysed to identify sibling species of the An. funestus group, none of which amplified using the available primers; two were infected with Plasmodium falciparum and Plasmodium ovale, separately, while 84% (n = 25) of the blood-fed specimens had fed on humans. Mitochondrial cytochrome c oxidase subunit 1 (cox1) and nuclear ribosomal internal transcribed spacer 2 (ITS2) sequences of 55 specimens (Plasmodium-positive, blood-fed and Plasmodium-negative) did not match reference sequences, possibly suggesting a previously unreported species, resolving as two clades.

Conclusions: Our findings indicate the existence of yet-to-be identified and described anopheline species with a potential as malaria vectors in Kenya.

Keywords: Anopheles funestus group; Dry ecology; Entomological surveillance; Kenya; Malaria transmission; Molecular approaches.

Fig. 1

Maximum-likelihood tree inferred for mosquito specimens encountered in this study. a ITS2 sequences using a JC model (267–763 bp). b cox1 barcode region using a GTR+G model (615–658 bp). Analysis was performed in MEGA v.6 with bootstrap support values based on 1000 replications shown above nodes. Other reference anopheline species are included for comparison. The scale-bar indicates the number of substitutions per site. Study samples with Plasmodium infection are indicated with red block circles, and those with blood meals from humans or goats are highlighted in green and grey, respectively. Taxon abbreviations denote samples analysed with haplotype sequences corresponding to GenBank accession nos: a ITS2 (540–538 nt; MK043038-MK043040). b cox1 (528–646 nt; MK047664-MK047672)