The epidemiological trend of cutaneous leishmaniasis in Kegalle district, Sri Lanka: A newly established disease focus and assessment of bioclimatic suitability for disease establishment using ecological niche modelling

Abstract

Cutaneous leishmaniasis is prevalent in Sri Lanka since 1992. It remains as a health issue with increasing numbers and spreading from endemic to non-endemic areas in the county. Kegalle district is a new disease focus, which notified the first case in 2016. However, there is no documented evidence of the vector distribution, abundance and potential risk factors in this district. Two Medical Officer of Health (MOH) areas (Rambukkana and Warakapola) that had reported the highest numbers of cases in the Kagalle district was selected and recorded cases (2016-2020) were obtained. The patients were visited and socio-economic, demographic, environmental and awareness-related information was collected using an interviewer-administered questionnaire. Entomological surveys were conducted from July 2019- July 2020 using three standard entomological techniques. Bioclimatic suitability for the disease transmission was evaluated using ecological niche modelling. A total of 107 patients were reported from both MOH areas and 88 were recruited for the study. The study showed that leishmaniasis in the Kegalle district progressed to an outbreak level within 3 years after reporting the first case. School students (n = 22, 25%, P < 0.05) and individuals between 11 and 20 years of age (n = 33, 37.5%, P<0.05) were identified as the main risk groups, while the presence of composting sites (n = 65, 73.9%, P < 0.05), abandoned lands (n = 63, 71.6%, P < 0.05) in the surrounding and suboptimal (dark or normal) lighting conditions (n = 87, 98.8%, P < 0.05) in the house were identified as main risk factors. Areas closer to the adjacent district (Kurunegala), which is a known endemic district for leishmaniasis indicated a high probability (0.3-0.5) for disease transmission. Sergentomyia zeylanica (n = 164, 56.94%), was identified as the predominant sand fly species followed by Phlebotomus argentipes (n = 121, 42.01%), Sergentomyia babu insularis (n = 2, 0.69%) and Sergentomyia punjabensis (n = 1, 0.35%). Phlebotomus argentipes was captured mostly for outdoor resting sites and S. zeylanica was recoded from both indoor and outdoor. The presence of vectors that can transmit leishmaniasis in these areas along with the potential risk factors could increase the transmission risk and disease establishment in new areas that are ecologically favourable for disease transmission. Therefore, vector control entities should undertake immediate measures to stop spreading the disease into new areas.