Résumé
A treated hessian fabric device for emanating the volatile pyrethroid transfluthrin was recently developed in Tanzania that protected against night-biting Anopheles and Culex mosquitoes for several months. Here these same emanator devices were assessed in the coastal tropical cities of Dar es Salaam in Tanzania and Port-au-Prince in Haiti, as a means of protection against day biting Aedes vectors of human arboviruses. Under semi-field conditions in large cages in Tanzania, 50 to 60% reductions of landing rates of Ae. aegypti were observed, regardless of which transfluthrin dose, capture method, emanator placement position, or source of mosquitoes (mildly pyrethroid resistant wild caught Ae. aegypti or pyrethroid-susceptible colonies of Ae. aegypti and An. gambiae) was used. Gas chromatography-mass spectrometry indicated that air samples collected in Tanzania immediately downwind from an emanator treated with the highest transfluthrin dose (15g) contained 12 to 19 μg/m3 transfluthrin vapour, which might be high enough to be a cause for concern. Also, several different full field experiments across Tanzania and Haiti with a variety of emanator designs, transfluthrin formulations and use practices consistently indicated negligible reduction of human landing rates by wild Aedes, largely Ae. aegypti. On the other hand, however, many community end users in Haiti, who were provided with these devices for their own use, viewed emanators positively and several outlined various advantages over current alternatives, although some expressed concerns about smell, health hazards, bulkiness, unattractiveness and future cost. Most participants expressed moderate to high satisfaction with protection against mosquitoes, especially indoors. Diverse use practices were reported, some of which probably targeted nocturnal Culex resting indoors, rather than Aedes attacking them outdoors during daylight hours. Some participants considered emanators superior to fans, bedsheets, sprays and coils, but it is concerning that several preferred them to bed nets and consequently stopped using the latter. These perspectives shared by Haitian end-users are consistent with those from similar studies in Brazil and recent epidemiological evidence from Peru that other transfluthrin emanator products can protect against arbovirus infection. While these encouraging sociological observations contrast starkly with the entomological evidence of essentially negligible effects upon Aedes landing rates from parallel entomological assessments across Haiti, Tanzania, Brazil and Peru, no other reason to doubt the generally encouraging views expressed herein by Haitian end users could be identified.