Malaria outbreak investigation in a rural area south of Zimbabwe: a case-control study

Ninety percent of the global annual malaria mortality cases emanate from the African region. About 80-90% of malaria transmissions in sub-Saharan Africa occur indoors during the night. In Zimbabwe, 79% of the population are at risk of contracting the disease. Although the country has made significant progress towards malaria elimination, isolated seasonal outbreaks persistently resurface. In 2017, Beitbridge District was experiencing a second malaria outbreak within 12 months prompting the need for investigating the outbreak.

An unmatched 1:1 case-control study was conducted to establish the risk factors associated with contracting malaria in Ward 6 of Beitbridge District from week 36 to week 44 of 2017. The sample size constituted of 75 randomly selected cases and 75 purposively selected controls. Data were collected using an interviewer-administered questionnaire and Epi Info version 7.2.1.0 was used to conduct descriptive, bivariate and multivariate analyses of the factors associated with contracting malaria.

Fifty-two percent of the cases were females and the mean age of cases was 29 ± 13 years. Cases were diagnosed using rapid diagnostic tests. Sleeping in a house with open eaves (OR: 2.97; 95% CI 1.44-6.16; p < 0.01), spending the evenings outdoors (OR: 2.24; 95% CI 1.04-4.85; p = 0.037) and sleeping in a poorly constructed house (OR: 4.33; 95% CI 1.97-9.51; p < 0.01) were significantly associated with contracting malaria while closing eaves was protective (OR: 0.45; 95% CI 0.20-1.02; p = 0.055). After using backward stepwise logistic regression, sleeping in a poorly constructed house was associated with five-fold odds of getting sick from malaria (AOR: 8.40; 95% CI 1.69-41.66; p = 0.009). Those who had mosquito nets did not use them consistently. The district health team and the rural health centre were well prepared to response despite having limited human resources.

Health promotion messages should emphasize the importance of closing the entry points of the malaria vector, and the construction of better houses in the future. Residents had to be educated in the importance of consistent use of mosquito nets. The district had to improve malaria preventive measures like distribution of mosquito nets and lobby for more human resources to assist with malaria surveillance thus, curbing the recurrence of malaria outbreaks.