Use of effective lids reduces presence of mosquito larvae in household water storage containers in urban and peri-urban Zika risk areas of Guatemala, Honduras, and El Salvador

The focus of this study is on household vector control activities, specifically the use of effective lids to prevent the presence of mosquito larvae in household water storage containers. Aedes aegypti mosquitoes are a challenge for vector control efforts due to their ability to breed in small amounts of water and their highly anthropophilic nature. The immature aquatic stages of the mosquito, including pupae and larvae, are considered to be the most effective target for household vector control. However, implementation is challenging due to the mosquito's ability to reproduce in small amounts of water and the fact that their eggs can survive for more than a year in a dry state. Households in the LAC region store water to fulfill basic needs related to cleaning, cooking, and drinking. This water often reaches the home through a piped water supply system managed by the local government. Although the piped water is often unsafe for drinking, it should not contain mosquito larvae. However, once stored in containers, the stagnant water may create potential mosquito breeding sites. Several behaviors are being promoted as part of an integrated vector management strategy, including visits from vector control workers and individual household behaviors such as throwing out tires where water accumulates, cleaning water storage containers at least weekly, and covering containers with lids. Studies from other regions have found that the use of lids is effective in preventing the presence of mosquito larvae in containers. A recent review states that there is a lack of reliable evidence regarding what vector control methods are effective for reducing the abundance of Aedes larvae, particularly with few rigorous study designs such as randomized trials. Covering water containers with lids has long been promoted to prevent Ae. aegypti breeding sites, but their effectiveness in research studies is not clear-cut. For lids to be effective, they should not have holes, should hermetically seal the container, and should not have water accumulated on them, creating a secondary breeding site on the lid. A study in Thailand found that the correct use of lids was effective in reducing the presence of larvae in jars used for storing water, but frequent use of the lids reduced their effectiveness. A separate study in Mexico and Venezuela found that insecticide-treated water covers significantly reduced the number of larvae. This study is the first to provide evidence on the use of different types of washbasins, containers, and lids in the LAC context and to explore the association between the use of an effective lid and the presence of larvae. The study found that using an effective lid versus no lid was associated with a 94% reduction in the odds of larval presence in long-term water storage containers.