Mosquito Trap to Curb Dengue



“What is an Ovitrap” by Nancy Brown
The Token Store provides opportunities for the unemployed in San Juan Cosalá to earn tokens which they use to purchase clothes and household items for their families. The store has taken on another project, quite a big one. Last year, San Juan Cosalá had a large number of cases of dengue fever.  The town was routinely sprayed with chemicals, but that didn’t seem to slow the number of cases.  I have done some research on the problem of dengue carrying mosquitoes and there doesn’t seem to be a chemical-free trap that actually kills them. Providing spray with Deet for the town is cost prohibitive. What does show real promise for helping the situation is ovitraps, used with great success by the U.S. military in areas where malaria is a serious problem.

I have experimented with several materials and have a simple-to-make and inexpensive prototype.  We are working with Lola, the Delegata of San Juan, and physicians from the clinic to get these ovitraps into the households.  We are training residents of the town to make them.  The actual cost to make one is about 20 pesos, and Lola feels that most people in the town can afford that.  We will, however, need to pay the trained locals who make them a small amount for each.   So we are hoping for sales of these to the expat community for 50 pesos each, which would help pay the people to make them and to provide free ones to the sick, elderly, disabled, etc. of the town, for which even 20 pesos would be a hardship.

Here is how our ovitrap works. Mosquitoes prefer to lay their eggs on or near stagnant water and they are attracted to dark colors.  A man’s sock, (black and thick is best) is siliconed to the bottom of a yogurt or large cottage cheese plastic container.  Holes are made for the wire for hanging the trap, and a larger overflow hole is placed about 20% down from the top.  The trap will come with a few pieces of dog food in the bottom, which when water is added, in a few days will create yucky water.  The water is wicked up by the sock.  The mosquitoes will lay their eggs on the rim of the container.  When the larvae develop, they will crawl and drop through the small-holed metal screen on the top as they are seeking the water.  When the larvae mature into mosquitoes, they are too big to get back out through the screen.  A plastic screen is glued over the overflow hole to keep them from exiting by that route.

The top screen can be occasionally taken off to remove dead mosquitoes. The process takes about 6 weeks to be fully effective and it is supposed to eliminate 98% of the mosquitoes.  About 4-6 ovitraps are needed for an acre of land, so each household in San Juan Cosalá would need only one.

If you could collect the large plastic yogurt or cottage cheese containers, the white wire clothes hangers (they are light weight and easier to cut, but will support the weight of the water) twist ties, and even old (or new) men’s black socks, we would greatly appreciate it.  These donations can be dropped off at the government building on the San Juan Cosalá square or I can arrange for times to drop off at locations closer to you.

We know we can’t eradicate the disease, but we are hoping we can cut down on the number of cases.  If a person gets dengue for a second time, it is much worse, and last year many people who had other health problems were hospitalized with dengue.  Thank you for supporting this cause! If you would like to order one or more of the ovitraps for yourself or your housekeeper or gardener’s families, you can send an order to me at


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