Susceptibility to malaria during the Prevention of Re-establishment phase in Sri Lanka
Authors: Jeevatharan Hamsananthy , AR Wickremasinghe 
Published: December 2020

Abstract
BackgroundSri Lanka eliminated malaria in November 2012 and was certified as malaria-free by the WHO in September 2016. However, influx of travelers from malarious countries and the presence of malaria vectors in formerly endemic areas make the country both receptive and vulnerable to re-establishment of malaria. As imported cases are still being reported and one introduced malaria case was reported in 2018, prevention of re-establishment of malaria is a challenge for Sri Lanka.Susceptibility to malaria is the predisposition of populations to be infectedby malaria parasites.It is influenced by the age-sex composition, parasitaemia, immunity, pregnancy status, type of residency, socio economic status, migration history of the population; broadly biological and generic factors. Therefore, addressing susceptibility to malaria is crucial for planning and implementing appropriate interventions to sustain malaria-free status of the country.The aim of this study was to assess susceptibility to malaria during the prevention of re-establishment phase in Sri Lanka.MethodsA national survey was conducted among 3,454 households. A multistage cluster sampling technique was used to select the households. Susceptibility was assessed based on pre-defined variables by interviewing heads of households using an interviewer-administered questionnaire. Basic socio-demographic information, travel history, history of fever and past malaria infections in the preceding three years were collected. Data were analyzed using SPSS version 20 package.ResultsThe proportion of population who had been overseas within the last 3 years in the urban sector (4.5%, n=99) was significantly higher than that of the rural (2.8%, n=288) and estate sectors (0.2%, n=2) (χ42=66.103; p<0.001). The proportions reporting overseas travel declined significantly with the wealth index up to the 4thquintile with a slight rise in the 5th quintile (χ82=60.985; P<0.001). In the multivariate analysis, persons from the urban sector were 1.75 times (95% CI 1.38-2.22) more likely to travel overseas as compared to persons from the rural and estate sectors; persons from the upper wealth index quintile were 1.46 times (95% CI-1.16-1.92) more likely to travel overseas than persons from the 1st and 2nd wealth index quintiles after controlling for gender, age group and area of residence. .There were 177 persons who had fever within the past 2 weeks of the survey. None of the surveyed population had malaria parasites on blood examination.Conclusions Urban residents, upper socioeconomic class persons and male gender are more likely to travel overseas and bring the parasite into the country. The malaria screening and awareness programmes should be targeted to these populations during the re-establishment of malaria phase as travel overseas is the most important criterion to assess susceptibility in an island nation.As susceptibility is a dynamic phenomenon, itshould be assessed periodically. Combining it with resilience and receptivity, social vulnerability and risk of re-establishment of malaria could be assessed.