Insecticide-treated materials for malaria control in Latin America: to use or not to use?

Abstract

Studies on the protective efficacy of insecticide-treated materials (ITMs) in Plasmodium vivax endemic areas of Latin America have not yielded sufficient evidence for recommendation of their extensive use in the region. Therefore 2 randomized community trials have been conducted on the Pacific Coast of Nicaragua which analysed the minimum coverage of ITMs needed to be effective against malaria. For the characterization of the study area, epidemiological and entomological baseline surveys and household interview surveys were undertaken. Thereafter the communities were paired (6 pairs in the 1st year and 13 pairs in the 2nd year) according to 4-monthly reported malaria incidence rates, population size and bednet coverage, and then randomly allocated to intervention and control groups. In the intervention groups, bednets were impregnated with lambdacyhalothrin; in the control groups, people received general health education. Anopheles albimanus was found to be the main vector with marked indoor biting behaviour late in the evening. P. vivax (99%) clearly outweighed P. falciparum (1%) with low parasite prevalence rates in the asymptomatic general population (8%) and low parasite densities. The protective efficacy of ITMs varied according to the coverage achieved: protective efficacy was 68% in communities with an average ITM coverage of 50% (10 pairs); 31% in communities with an ITM coverage of 16-30% (4 pairs); and no protective efficacy in communities with ITM coverage below 16% (5 pairs). The comparison with other P. vivax endemic areas in Latin America showed that the vector's late biting behaviour and the indoor preference (where ITMs have a repellent effect) probably led to the favourable results in the study. In malaria endemic areas of Latin America, where P. vivax is predominant, studies on vector behaviour should be conducted in order to predict the impact of ITMs on malaria transmission.

Malaria: current status of control, diagnosis, treatment, and a proposed agenda for research and development

“…The effectiveness of insecticide-treated mosquito nets varies with the rate of malaria transmission; the nets do not work well in many areas of low and unstable transmission, where malaria vectors bite in the early evening and morning. 23 Further work remains to be done on new combinations of insecticides and fabrics. More information is also needed on the relation between the extent of community use of insecticide-treated mosquito nets and malaria morbidity, mortality, and transmission.…”

Community cooperatives and insecticide-treated materials for malaria control: a new experience in Latin America

“…Insecticide-treated materials (ITMs) have a mean protective efficacy against malaria episodes of roughly 50% in highly endemic areas of Africa [1] and of 40% in lower endemicity areas of Latin America where either P. vivax or P. falciparum are predominant [2,3]. Other trials have shown that ITMs are also protective against the transmission of Chagas' disease [4] and of cutaneous leishmaniasis [5] making them one of the most powerful weapons against disease-transmitting vectors.…”

Efficacy of Some Wearable Devices Compared with Spray-On Insect Repellents for the Yellow Fever Mosquito, Aedes aegypti (L.) (Diptera: Culicidae)

“…Application of the repellent DEET to ankles and feet of the population in an African village significantly reduced the incidence of malaria (Durrheim and Govere 2002). Repellent soaps that contain DEET and permethrin have been shown to successfully reduce malaria infections (Kroeger et al 1997, Kroeger et. al., 1999).…”