During pregnancy, women are particularly susceptible to malaria infection due to changes in their immune responses. Malaria can cause maternal anemia, intrauterine growth restriction, stillbirth, prematurity, and associated morbidity and mortality.
Mechanism of Action
Mosquito nets provide a physical barrier from the insects which is especially important at night when mosquitoes that carry malaria are most active. There are three main types of nets. Conventional nets can be made from cotton, nylon, polyester, or polyethylene, and only provide a physical barrier. A mesh count of 156 holes per square inch or more is recommended. Conventional Insecticide Treated Nets (ITNs) improve efficacy through the use of permethrin or deltamethrin, which repel, kill, or disable mosquitoes. For conventional ITNs, the insecticide must be re-applied to the net every 6 months. Historically, compliance with re-treatment recommendations has been low. The WHO now recommends the use of Long Lasting Insecticidal Nets (LLI Ns) which require no retreatment. The insecticides used in LLI Ns are either incorporated into the net material itself, or permanently coated over the net fibers. LLI Ns are designed to provide protection for up to 3 years.
Current use in High-Resource Settings:
Window screens and extensive use of air conditioning help to keep sleeping quarters mosquito-free in high-resource settings. LLINs may also be used where mosquitoes are present.
Application to Low-Resource Settings:
Conventional, untreated nets are readily available in urban marketplaces in areas of high malaria prevalence. Increasingly, donor driven campaigns of subsidized (or free) LLINs are reaching further and further into rural areas through several channels. Social marketing organizations are making LLINs widely available through retail drug sellers around the world. Donor-driven campaigns give mosquito nets away for free at special events. Free, or heavily subsidized net distribution is increasingly common in antenatal clinics. There has been considerable debate on the appropriate subsidy level for mosquito nets, but randomized controlled trials have shown that in the case of pregnant women in Kenya, free (as opposed to subsidized) net distribution saves more lives.