Prevalence of Wuchereria bancrofti and Plasmodium falciparum Infection in Anopheles Mosquitoes and Human Blood Sampled from Matayos in Busia County, Western Kenya

Abstract

Lymphatic filariasis and malaria are mosquito-transmitted diseases that are simultaneously endemic in several regions of Kenya. Despite control efforts, malaria continues to cause significant morbidity and mortality globally, with an estimated 249 million cases and over 610,000 deaths reported in the year 2025 while lymphatic filariasis is associated with chronic disability including lymphoedema and hydrocele, with approximately 657 million people in 44 countries still requiring preventive chemotherapy. This cross-sectional study evaluated the simultaneous presence of the parasites responsible for lymphatic filariasis and malaria, namely Wuchereria bancrofti and Plasmodium falciparum, in both human hosts and anopheline mosquito populations from Matayos Constituency in Busia County, western Kenya where new cases of Lymphatic filariasis had been newly reported.292 Adult Anopheles mosquitoes were collected inside the houses of the 92 participants who tested positive by Filarial Test Strip. Field sampling was conducted to obtain mosquitoes belonging to the Anopheles gambiae and Anopheles funestus species complexes, which were subsequently analyzed by Polymerase Chain Reaction (PCR) to detect infections with Wuchereria bancrofti and Plasmodium falciparum. A total of 292 female Anopheles mosquitoes, together with 92 human blood specimens, were obtained and processed for laboratory analysis. PCR-based species identification was successful for 288 mosquitoes, corresponding to 98.63% of the collected specimens. Among the identified mosquitoes, members of the An. funestus complex predominated, accounting for 247 individuals (85.76%), whereas the An. gambiae complex contributed 41 specimens (14.24%). No specimens belonging to An. parensis or An. vaneedeni, both recognized members of the An. funestus complex, were detected in the sample population. Molecular screening revealed two mosquito infections with Wuchereria bancrofti, one occurring in An. leesoni and the other in An. funestus. These findings correspond to infection prevalences of 0.46% and 4.17% for the respective species. No evidence of Plasmodium falciparum infection was observed in either the mosquito specimens or the human blood samples analyzed. In contrast, Wuchereria bancrofti was detected in two blood samples, corresponding to a prevalence of 2.17%. Phylogenetic characterization based on partial 18S rRNA gene sequences of W. bancrofti demonstrated a high degree of genetic similarity to isolates previously reported in other studies. Furthermore, neither the mosquito samples nor the human blood specimens showed concurrent infections involving both P. falciparum and W. bancrofti. Overall, the predominance of Anopheles funestus mosquitoes within the study area calls for the implementation of effective vector control strategies to reduce mosquito population and minimize disease transmission. The detection of Wuchereria bancrofti in both Anopheles mosquitoes and human blood samples in Busia County indicates ongoing transmission of lymphatic filariasis. Therefore, there is a need to strengthen case detection and implement appropriate treatment programs for affected individuals to reduce the disease burden and interrupt transmission. The strong phylogenetic similarity observed between the isolates analyzed in this study and those reported from other endemic areas underscores the importance of ongoing molecular epidemiological monitoring. Continuous surveillance can support the timely identification of novel genetic changes, inform disease elimination strategies, and enhance understanding of the spatial distribution and transmission patterns of Wuchereria bancrofti strains across different regions.