Malaria epidemic and transmission foci in highland of Kisii, western Kenya

Background: The vulnerable population within the malaria epidemic zone remains at risk of increased burden and fatality. This is because of unpreparedness and overstretching of healthcare capacity in the event of a full-fledged epidemic. The purpose of this study was to determine the prevalence of microscopic and submicroscopic infections, as well as map specific Plasmodium transmission foci, in the malaria epidemic-prone zone of Kisii highland.Methodology: Patients seeking malaria treatment at Eramba health facility in the epidemic-prone zone of Kisii highland were enrolled in the study. Malaria outpatient data for the entire month of May were also included in the analysis. Patients' finger prick blood smears were examined for microscopic infections, while a real-time polymerase chain reaction targeting the Plasmodium species 18S rRNA gene was used to detect the presence of submicroscopic infections on DNA extracted from dry blood spots.Results: Based on outpatient data, the malaria positivity rate was 20.7% (231/1115, 95% CI, 0.18-0.23). The positivity rate varied significantly by age group (chi 2 = 75.05, df 2, p < 0.0001). Children under the age of five had the highest positivity rate (27.8%, 78/281), followed by children aged 5-15 years (19.4%, 69/356), and individuals aged 15 years and above (17.6%, 84/ 478). Out of the 102 patients recruited, the positivity rate by microscopy was 57.8% (59/102) and 72.5% (74/102) by RT-PCR. Most of the microscopic infections (40.7%, 24/59) were from Morara and Nyabikondo villages in Rioma and Kiomooncha sublocations, respectively. The submicroscopic prevalence was 14.7% (15/102) and was observed only in patients from highinfection villages in Rioma (15.8%, 9/57) and Kiomooncha (16.2%, 6/37) sublocations. Across gender and age groups, females (19.7%, 12/61) and patients aged 15 years and above (21.1%, 8/ 38) had high levels of submicroscopic infections. There were two mixed infections of P. falciparum/P. malariae and P. falciparum/P. ovale, both from patients residing in Kiomooncha sublocation.Conclusion: Plasmodium falciparum infections remained relatively high in the Marani subcounty. Infections were concentrated in two villages, which could serve as a target for future public health intervention, particularly during a malaria epidemic.