Is staying overnight in a farming hut a risk factor for malaria infection in a setting with insecticide-treated bed nets in rural Laos?

Daisuke Nonaka,Keobouphaphone Chindavonsa,Samlane Phompida,Jun Kobayashi,Junko Yasuoka,Masamine Jimba,Sakhone Laimanivong,Viengxay Vanisaveth,Shigeyuki Kano

doi:10.1186/1475-2875-9-372

Abstract

BackgroundOvernight stays in farming huts are known to pose a risk of malaria infection. However, studies reporting the risk were conducted in the settings of poor net coverage. This study sought to assess whether an overnight stay in a farming hut is associated with an increased risk of malaria infection if insecticide-treated bed nets (ITNs) are properly used.MethodsA pair of cross-sectional surveys was carried out in the Lamarm district of Sekong province, Laos, in March (dry season) and August (rainy season) in 2008. Questionnaire-based interviews and blood examinations were conducted with farmers and their household members from three randomly selected villages in March (127 households, 891 people) and August (128 households, 919 people). Logistic regression analysis, adjusted for potential confounding factors, was used to assess the association between malaria infection status and frequency of overnight stays for the two weeks prior to the study in both the seasons.ResultsIn March, 13.7% of participants reported staying overnight in a farming hut at least once in the previous two weeks. The percentage increased to 74.6% in August. Not only adults but also young children stayed overnight as often as adults. The use of an ITN the preceding night was common both in farming huts (66.3% in March, 95.2% in August), and in main residences (85.8% in March, 92.5% in August). Logistic regression analysis showed no statistical association between malaria infection status and frequency of overnight stays in farming huts in either study period. However, people sharing one family type net with five people or more were significantly more likely to have malaria than those sharing a net with up to two people in the dry season.ConclusionsThis study showed that staying overnight in farming huts was not associated with an increased risk of malaria infection in the setting where ITNs were widely used in farming huts. It suggests that malaria infection during overnight stays in farming huts might be preventable if ITNs are properly used in rural Laos.

Highlights

Overnight stays in farming huts are known to pose a risk of malaria infection
Most main residences had a window without mosquito-proof net, main residences appeared to be more protected than farming huts in terms of mosquito invasions
This finding was in line with that of the Tanzania study that reported no association between overnight stays in the farming huts and incidence of febrile illness episodes in the malaria endemic area of the country [6]

Summary

Introduction

Overnight stays in farming huts are known to pose a risk of malaria infection. Studies reporting the risk were conducted in the settings of poor net coverage. This study sought to assess whether an overnight stay in a farming hut is associated with an increased risk of malaria infection if insecticide-treated bed nets (ITNs) are properly used. Most of the population lives in rural areas and 84% of the households are engaged in rice farming [3]. In Thailand, movements entailing overnight stays on farms occur throughout the year for rice cultivation, and peaked between June and September [5]. A study in Tanzania showed that most of the studied population stayed overnight in huts for weeding in February and harvesting rice in May [6]

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Results

Discussion

Conclusion