Malaria Outbreak Investigation in Pastoral Communities of BenaTsemay District, Southern Ethiopia: A Case Control Study

Over 60% (60 million) of Ethiopian populations live in areas at risk for malaria. On June 17 /2017, surveillance data from BenaTsemay district showed that the district was experiencing an unusual high number of malaria cases in three kebeles (lowest administrative unit). We investigated the outbreak to describe malaria epidemiology in the district, identify population risk factors, and guide intervention measures for the community. Malaria case records from the District Health Office were reviewed to describe the outbreak. Unmatched case-control study was conducted with 60 randomly selected cases and 119 controls using a semi-structured questionnaire. Malaria cases were confirmed by either microscopy or malaria rapid diagnostic tests (RDTs) from June 5 to July 23/2017. Controls were persons with no diagnosis of malaria, and lives in similar kebele. Environmental assessment, observation of ownership and utilization of insecticide treated bed-nets (ITNs) were carried out. Multivariable regression model analysis was conducted to identify independent malaria risk factors. There were 648 malaria cases (50.3%-males) from three kebeles with no deaths recorded. The overall attack rate (AR) was 114/1000 populations, and it was highest in Sille kebele (167/1000 populations) and among 5-14 years old (179/1000 populations). Age <5 years (AOR=8.5; 95%CI: 1.2-59), living near mosquito breeding sites (AOR=6.5; 95%CI: 1.15-36.5), irregular use of ITNs (AOR=8.7; 95%CI: 1.5-49.6), inadequate ITNs per family size (AOR=13.4; 95%CI: 1.9-93) predicted having of malaria. Wearing long sleeved clothes was a protective factor (AOR=0.6; 95%C.I: 0.004-0.96). Several unmanaged stagnated water sources with Anopheles mosquito larvae, and the use of ITNs for other purposes were observed. The outbreak was associated with presence of nearby vector-breeding sites, and poor access and utilization of ITNs. Adequate information should be given along ITNs for the community in addition to early management of nearby vector-breeding sites to prevent similar outbreak in future