A Hybrid Approach to Screen A Sentinel Population to Identify Clusters of Sub-Patent Malaria Infections in Low Endemic Setting In Batu Degaga Kebelle, Adama Woreda, Oromia, Ethiopia

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Addis Ababa University


Background: As the incidence of malaria decreases the distribution of malaria becomes highly heterogeneous and concentrated in certain geographical areas and households. Due to this the risk of being infected by malaria becomes highly variable within the same locality and households. Identifying the distribution patterns of malaria is crucial in the control as well as elimination of malaria. Methods: A cross sectional survey was carried out targeting a total of 18 rapid diagnostic test(RDT)-confirmed malaria infected and 18 individuals that visited the health-post for malaria unrelated cases between October and December 2016 including their immediate six neighbors and family members. Consenting individuals were screened for malaria using RDT and dried blood spots were collected for quantification of parasites using species specific 18S based quantitative polymerase chain reaction (qPCR). Spatial clustering of malaria infections was assessed using SaTScan Software. Results: RDT-detected malaria (any species) was higher in the community around index cases compared to controls (P = 0.001). Asymptomatic qPCR-detected P. falciparum infections were higher in the community around index cases (13.9%) compared to controls (9.5%; P = 0.038) while the distribution of qPCR-detected P. vivax was similar (P = 0.926). Children had the highest burden of malaria and carry high density infections compared to adults. SaTScan detected four geographically non-overlapping significant hotspot of any malaria cases with relative risk of 2.11, 1.9, 1.89 and 1.86. Individuals who lived in households (HHs) within at risk areas were more likely to have previous malaria episodes (33.1%, 177/233) compared to individuals in HHs outside risk areas (1.5%, 3/203; odds ratio [OR], 32.9; 95% CI, 10.2 – 106.3). People in risk areas utilize malaria control interventions better than people in HHs outside of risk areas and live in iron sheet houses with eave openings and better HH facilities. HHs within the clusters of higher malaria incidence was closer to water bodies and farther from health posts. People who lived in HHs at risk areas walk in the night, enter their houses late and leave their houses early than people who lived in risk free areas. Conclusion: The distribution of malaria was heterogeneous and clustered in the study district. Symptomatic and asymptomatic malaria distributed significantly around index cases compared to non-malaria control cases. Malaria control and elimination strategies of the country might benefit by targeting hotspots of malaria by following patients. Hot spot population carries the biggest burden of malaria and they might contribute disproportionately to the onward maintenance of malaria infections even outside of the risk areas Key words: Cluster, Asymptomatic, Heterogeneous, IX qPCR Sat Scan



Cluster; Asymptomatic; Heterogeneous; IX qPCR Sat Scan