Prevalence and factors associated with visceral leishmaniasis and distribution of sandfly vectors in Tiaty west sub county, Baringo County, Kenya

Abstract

Visceral leishmaniasis is a parasitic disease caused by Leishmania donovani, transmitted by Phlebotomine sandflies. It affects the reticuloendothelial system and causes high morbidity and mortality. Globally, an estimated 500,000 new cases occur annually. In Kenya, VL is endemic in arid and semi-arid regions such as Machakos, Kitui, Baringo, and West Pokot counties. Baringo County, specifically Tiaty Sub-County which has been historically hotspot for VL due conducive ecological climate, vegetation, pastoralist and housing which create ideal environment for sandfly survival. Multiple VL outbreaks have been reported in Tiaty sub counties as documented by Ministry of Health and WHO, therefore Chemolingot Sub County Hospital (CSCH) was selected as the study site and as main referral facility in Tiaty sub-county. The hospital serves as a primary health center for VL cases, however there is scarcity of data on disease prevalence and associated risk factors in patients attending the hospital. The study aimed to determine the prevalence of VL, determine associated risk factors, and establish the distribution, abundance and diversity of sandfly vectors. A hospital based cross-sectional study design coupled with an entomological field survey was used. A sample size of (331) patients was consecutively recruited using Fisher’s formula from a target population of 1,800. Blood samples were tested for VL using recombinant antigen, derived from a kinesin-like protein of leishmania chagasi, (rk39). This diagnostic kit is suitable for use in rural hospitals like CSCH. Socio-demographic data were collected using a pre- tested structured questionnaire. Sandflies were collected using castor oil sticky traps and CDC light traps which enhanced chances of capture. Traps were placed at five randomly selected sites in Lorwatum village, Tiaty West Sub County to ensure adequate representative sampling of diverse habitats. Traps were set between 17:00 and 06:00 hours to coincide with the peak activity period of sandflies which are nocturnal. Descriptive statistics was used to summarize prevalence and vector abundance. Chi-square tests assessed associations between variables and those statistically significant (p < 0.05) were further analyzed using binary logistic regression to estimate odds ratios. Captured sandflies were identified using standard taxonomic keys, Paleontological Statistics (PAST) v4.0. software was used to compute data. Shannon’s diversity index was calculated and further diversity t-tests done for significance difference in the 5 selected sites. The hospital-based prevalence of VL was 39.57% (131/331). Most participants were aged 1–10 years were 131 (38.57%). Significant risk factors for VL; unemployment (OR = 9.50, 95% CI: 3.30–27.40, p < 0.001) animals near compound (OR = 5.27, 95% CI ≈ 2.60–10.70, p < 0.001) house roof material (OR = 3.70, 95% CI: 2.10–6.50, p < 0.001), protective factors include awareness of VL transmission (OR = 0.20, 95% CI: 0.11–0.36, p = 0.001). Phlebotomus vectors were 8 (4.5%), with a male- female ratio 1:6.25. Sandfly diversity was highest indoors (Shannon diversity index H’ = 1.38; evenness = 0.66). Statistically significant differences in diversity were between inside house and tree holes’ t (7.97) = 17.51, p < .001 and between open fields and beehive t (7.79) = 5.96, p < .001. In conclusion, there is high prevalence of VL among patients at Chemolingot Sub County Hospital. Major risk factors included unemployment, house material, with Phlebotomus martini available in four habitats This study confirms the endemicity of VL in Tiaty Sub-County and highlights the importance of rapid diagnostic tools like rK39 in field settings. Strengthened surveillance, public awareness, and integrated control measures are recommended.