Insecticide-impregnated bednets appear to be a potentially cost-effective intervention against endemic malaria in the tropics, but this has yet to be confirmed by field trials. There are two aspects to consider in assessing such trials: (1) the extent to which subjects use nets regularly and properly, and (2) the effectiveness of nets which are truly used regularly and properly in reducing malaria transmission. The second aspect is currently of primary concern, to determine if human-vector relationships for a particular at-risk population are such that bednets can be effective. But to give bednets a "fair" test in this regard requires regular and proper use in the first place. The study described here suggests they did not get a "fair" test in one field trial in Sabah, East Malaysia. The study also strongly suggests that direct observations, rather than post hoc questioning of subjects, may be essential to accurately gauge bednet usage rates. Accurate usage rates are required to determine what proportion of a population needs to use nets to reduce malaria transmission, and to evaluate the effectiveness of promotional programs over time. Direct observations can also yield valuable data on night-time activities that increase malaria risk, such as television viewing that keeps people awake and out of bednets.
Observational and survey methodologies were used to probe human behavioral factors influencing the use of insecticide-impregnated bednets to control malaria in rural Sabah, Malaysia. One aim was to investigate why a field trial of such nets in an interior area yielded disappointing results. A second aim was to gather baseline data prior to a field trial proposed for a coastal area. Interior villagers reported a significantly higher net usage rate than that observed directly, suggesting that subject self-reports need to be validated in some way. The poor results of the interior field trial appeared related to reluctance to regularly use nets, which were not in wide use previously. Prospects for reducing malaria transmission through bednets appeared better for the coastal area since nearly half of observed villagers were sleeping in them. However, significantly more coastal than interior villagers were observed watching television at night, an activity that may increase malaria risk by keeping villagers awake and out of bednets.