Abstract
BACKGROUND: Visceral leishmaniasis (VL), also known as kala-azar, remains a major public health problem in Ethiopia, caused mainly by Leishmania donovani and transmitted through infected female Phlebotomine sandflies. The disease disproportionately affects impoverished, rural populations. Understanding the epidemiology and risk factors of outbreaks is vital for timely prevention and control. OBJECTIVE: This study was aimed to investigate a VL outbreak and associated risk factors among communities in South Omo Zone, Southern Ethiopia, 2022-2023. METHODS: A descriptive cross-sectional study followed by an unmatched case-control study (1:2 ratio) was conducted from June 2022 to January 2023. Forty-five laboratory-confirmed VL cases and ninety controls without previous VL history were included. Data on socio-demographic, environmental, and behavioral factors were collected using structured interviews. Logistic regression analysis was performed to identify independent risk factors, and the strength of association was expressed using adjusted odds ratios (AORs) with 95 % confidence intervals (CI). Statistical significance was set at p < 0.05. RESULTS: A total of 45 VL cases and 3 deaths were recorded, yielding an attack rate of 9.7 per 100,000 population and a case fatality rate of 7 %. The highest attack rate occurred in Salamago District (51.6/100,000), followed by Nyangatom (19.5/100,000). Adults were the most affected group (87 % of cases). The epidemic curve suggested a propagated outbreak peaking in week 24 of 2022. Independent predictors of VL infection included never using long-lasting insecticidal nets (LLINs) (AOR = 7.97; 95 % CI: 1.63-39.04), inconsistent LLIN use (AOR = 5.33; 95 % CI: 1.59-17.83), sleeping under acacia trees (AOR = 5.13; 95 % CI: 1.26-20.78), and living in houses with wooden walls (AOR = 6.62; 95 % CI: 2.07-21.25). CONCLUSIONS: The outbreak was concentrated in the Salamago District, predominantly affecting adult males. Inconsistent use of LLINs, outdoor sleeping under acacia trees, and poor housing conditions significantly increased VL risk. Strengthening vector control programs, promoting consistent LLIN utilization, improving housing quality, and enhancing community awareness are essential to prevent future VL outbreaks in pastoral settings.