Trend analysis and spatiotemporal distribution of leishmaniasis disease incidence in Sri Lanka: A detailed review from 2009 to 2023

Abstract

BACKGROUND: Leishmaniasis, a significant emerging and re-emerging zoonotic disease, has exhibited a marked increase in incidence globally and in Sri Lanka. Analyzing its incidence in different geographical locations provides insights into its transmission dynamics for designing and implementing control interventions. This study aimed to investigate the disease trends in Sri Lanka at the national level using statistical models. METHOD: Weekly records of leishmaniasis cases from 2009 to 2023 were accessed from the weekly epidemiology reports published by the Epidemiology Unit of the Ministry of Health, Sri Lanka. The incidence rate (IR) for each year for 25 administrative districts in Sri Lanka was calculated per 100,000 population using estimated population data published by the Department of Census and Statistics, Sri Lanka. The IR was modeled using a Generalized Additive Model for Location, Scale, and Shape (GAMLSS). Data were analyzed using R 4.4.0 software and gamlss, mgcv, sp, ggplot2, dplyr, and rgl packages. RESULTS: A total of 30,295 leishmaniasis cases were recorded, with Hambantota (68.32), Polonnaruwa (52.21), and Anuradhapura (40.30) districts reporting the highest IRs. These three districts, along with Matara (26.38), Matale (25.48), and Kurunegala (16.21), accounted for over 83% (n = 25,151) of reported cases. The IRs of Anuradhapura, Matale, Ratnapura, Kegalle, and Puttalam districts steadily increased over time after 2015 to almost 2.0 cases per 100,000 population by 2022. A seasonal variation is seen mid-year peaking around June to August. CONCLUSIONS: This study reveals temporally regressive and spatially expanding incidence of cutaneous leishmaniasis in Sri Lanka with characteristic geographical patterns and disease hotspots, highlighting the need for comprehensive control strategies to prevent further spread and mitigate the impact of leishmaniasis in the country.