The use of motion detectors to estimate net usage by householders, in relation to mosquito density in central Cote d’Ivoire: preliminary results

BACKGROUND: The difficulty of accurately assessing LLIN use has led us to test electronic data logging motion detectors to provide quantitative data on household LLIN usage. METHODS: The main movements associated with an LLIN when appropriately used for malaria control were characterised under laboratory conditions. Data output from motion detectors attached to the LLINs associated with these specific movements were collated. In preliminary field studies in central Cote d’Ivoire, a pre-tested and validated questionnaire was used to identify the number of days householders claimed to have slept under LLINs. This information was compared to data downloaded from the motion detectors. RESULTS: Output data recording movement on the x, y, and z axes from the data loggers was consistently associated with the specific net movements. Recall of LLIN usage reported by questionnaires after a week was overestimated by 13.6%. This increased to 22.8% after 2 weeks and 38.7% after a month compared to information from the data loggers. Rates of LLIN use were positively correlated with An.gambiae s.s biting density (LRT = 273.70; P < 0.001). CONCLUSION: This study showed that motion detectors can be used to provide a useful quantitative record of LLIN use. This new methodology provides a supplementary means of surveying bed net usage.