Association of microclimatic and edaphic factors with sandfly abundance and distribution in Bungoma county, Kenya

Abstract

Sandflies (Diptera: Psychodidae) are the only known primary vectors of leishmaniases including cutaneous leishmaniasis. Infected female phlebotomine sandflies pass Leishmania parasites to humans and animals as they bite for blood meals. Environmental microclimatic factors such as humidity, temperature, and soil characteristics affect sandfly abundance and distribution differently. Heterogenous environmental factors that pose potential disease risks exist in Bungoma County, with scanty studies documenting their relationships. The current study aimed to investigate the associations of environmental altitude, temperature, humidity and soil chemical and physical factors with sandfly abundance and distribution. A cross-sectional field survey was applied to collect sandflies from 12 cave habitats in 5 selected sub-counties in Bungoma County by use of Center for Disease Control and Prevention light traps. Cave ambient temperature, soil temperature, relative humidity, Geographical positioning system locations were measured and recorded on site, and a composited soil sample collected from each site was transported to a soil laboratory for physical-chemical analyses. Sandflies were collected once from each site every month for 24 months. Chi-square tests, one way analysis of variance (ANOVA) and Pearson’s correlation tests (p<0.05) were used for data analysis. Temperature and relative humidity significantly (p<0.05) correlated with sandfly abundance and distribution. Short rain seasons (October-December) recorded the peak abundance of sandflies (p=0.2611). soil physical and chemical factors nonsignificantly correlated with sandfly abundance in the sampled sites. Altitude, relative humidity and temperature are key determinants of sandfly abundance and distribution in Bungoma County. Vector management strategies should be planned to target the peak season of sandfly abundance (OctoberDecember) for effective cutaneous leishmaniasis control.