Risk factors associated with malaria outbreak in Laelay Adyabo district northern Ethiopia, 2017: case-control study design

BACKGROUND: Globally in 2015 about 214 million malaria cases and 438,000 deaths were reported with 75% were from Sub-Saharan Africa. Malaria transmission in Ethiopia is unstable, and outbreaks are considered public health emergencies. Understanding the trigger for outbreaks in low-transmission areas can help facilitate malaria elimination. On July 8th malaria outbreak was reported from Laelay Adyabo district. The objective was to investigate the magnitude and associated factors with malaria outbreak. METHODS: We defined a case as confirmed malaria using microscopy or a rapid diagnostic test for Plasmodium parasites in a resident of Laelay-Adyabo District from July 9–28, 2017. We identified cases by reviewing health facility records and conducted a case-control study using randomly-selected cases from a line list, and two neighborhood controls per case. A pretested semi-structured questionnaire adapted from WHO malaria guidelines was used to collect data from case-patients and controls. We calculated crude (COR) and adjusted (AOR) odds ratios to identify factors associated with malaria. RESULT: A total of 145 confirmed malaria cases (57.9% males) were identified with village attack rate (AR) of 12.1/1000. The AR was higher among males than females (14.1 verses 10.1/1000), children aged 5–14 years (12.9/1000), and in Zelazle Kebelle (13.6/1000 population). Wearing protective clothing (AOR = 0.27, 95% CI 0.11–0.66), having good knowledge of malaria transmission (AOR = 0.25, 95% CI 0.08–0.75), having waste collection material at home (AOR = 0.25 95% CI 0.11–0.61), availability of mosquito breeding sites around home (AOR = 9.08, 95% CI 3.6–22.93), and staying outdoor overnight (AOR = 3.7, 95% CI 1.44–9.56) were independently associated with malaria. CONCLUSION: The overall attack rate for malaria during this outbreak was high affecting > 1% of the population. Wearing protective clothing at night, knowing about malaria transmission, having mosquito breeding sites around the home, staying outdoors overnight, and having waste collection material in their house were predictors of the infection. Laelay Adyabo district health office should provide health education on malaria transmission and prevention measures and how to clear mosquito breeding sites. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12889-019-6798-x) contains supplementary material, which is available to authorized users.