Assessing malaria risk at night-time venues in a low-transmission setting: a time-location sampling study in Zambezi, Namibia

Malar J. 2019 May 22;18(1):179. doi: 10.1186/s12936-019-2807-x.


Background: Identifying efficient and effective strategies to reach and monitor populations at greatest risk of malaria in low-transmission settings is a key challenge for malaria elimination. In Namibia's Zambezi Region, transmission is ongoing yet its drivers remain poorly understood. A growing literature suggests that night-time social activities may lead to malaria exposure that is beyond the reach of conventional preventive interventions, such as insecticide treated bed nets and indoor residual spraying.

Methods: Formative research was conducted with community members in March, 2015 in the catchment areas of six randomly selected health facilities in the western Zambezi Region to identify night-time locations where large numbers of individuals regularly congregate. Using time-location sampling, a survey was conducted between March and May, 2015 at community-identified venues (bars and evening church services) to develop representative estimates of the prevalence of parasite infection and risk factors among venue-goers.

Results: When compared to a contemporaneous household survey of the general population aged 15 and older (N = 1160), venue-goers (N = 480) were more likely to have spent the night away from their home recently (17.3% vs. 8.9%, P = 0.008), report recent fever (65.2% vs. 36.9%, P < 0.001), and were less likely to have sought care for fever (37.9% vs. 52.1%, P = 0.011). Venue-goers had higher, but not significantly different, rates of malaria infection (4.7% vs. 2.8%, P = 0.740). Risk factors for malaria infection among venue-goers could not be determined due to the small number of infections identified, however self-reported fever was positively associated with outdoor livelihood activities (adjusted odds ratio [AOR] = 1.9, 95% CI 1.0-3.3), not wearing protective measures at the time of the survey (AOR = 6.8, 9% CI 1.4-33.6) and having been bothered by mosquitos at the venue (AOR = 2.7, 95% CI 1.5-4).

Conclusions: Prevention measures and continued surveillance at night-time venues may be a useful complement to existing malaria elimination efforts.

Keywords: High-risk populations; Malaria; Namibia; Surveillance; Time-location sampling.

MeSH terms

  • Adolescent
  • Adult
  • Animals
  • Anopheles / parasitology
  • Darkness*
  • Female
  • Humans
  • Insecticide-Treated Bednets / statistics & numerical data
  • Leisure Activities
  • Malaria / prevention & control
  • Malaria / transmission*
  • Male
  • Middle Aged
  • Mosquito Control / methods*
  • Namibia / epidemiology
  • Prevalence
  • Risk Assessment
  • Risk Factors
  • Sampling Studies
  • Surveys and Questionnaires
  • Young Adult