Donate to this project. Help to free more communities from mosquitoes, Zika, and dengue fever.
For years, Aedes aegypti mosquitoes and dengue fever were a regular part of life in Monte Verde, a humble peri-urban community in Honduras. Then, in 2016, Monte Verde was overrun not only with dengue but also with Zika and chikungunya. All of these diseases were transmitted by Aedes aegypti. Desperate, and with help from a nonprofit organization, the community embarked on a pioneering effort to get rid of the mosquitoes and the diseases. Monte Verde residents used biological control with copepods, baby turtles, and tilapia fingerlings, all of them highly effective predators of mosquito larvae, to prevent mosquito production in wells and containers such as small cement tanks and plastic drums used to store water for household use. While biological control involved virtually no cash expense, it did require full community participation to ensure that it worked. The key was a small team of community volunteers, who worked with their neighbors to achieve success. After more than a year of experimentation, working out the details of how to do it, and overcoming numerous technical and social obstacles, Monte Verde volunteers and residents crafted an environmentally friendly mosquito eradication toolkit that works effectively and sustainably. Mosquito production from wells and water storage containers is now zero. Most important, there have been no cases of Zika, dengue, or chikungunya since the beginning of 2017. Monte Verde can serve as a model for extending the same success to other communities.
A single species of mosquito (Aedes aegypti) is one of the most serious health threats on the planet. It’s responsible for Zika, dengue fever, chikungunya, and yellow fever. Since the World Health Organization’s global DDT campaign to eradicate mosquito-borne diseases collapsed in the 1970s, dengue fever has increased to hundreds of millions of cases worldwide each year, with half-a-million children hospitalized annually because of life-threatening complications, and 20,000 fatalities. Chikungunya, Zika, and birth defects due to Zika have spread through Latin America in recent years.
The Aedes aegypti mosquito, which is responsible for Zika, dengue fever, chikungunya, and yellow fever, has a characteristic “lyre” design on its back.
Because there is no vaccine for these diseases (except yellow fever), the only way to control them is by going after the mosquito, but there has been little progress despite hundreds of billions of dollars spent worldwide on insecticides over the years. In fact, it’s getting worse, and with Global Climate Change, the diseases threaten to spread from the tropics into North America and Europe. Large sums of money are now being spent on developing genetic engineering approaches such as GMO mosquitoes. We don’t know how effective these new methods will be, but we can be sure that they will be expensive.
An alternative approach
Is there another way? The pioneering success of Monte Verde, a community of 350 houses in the municipality of Choloma, Cortés, near San Pedro Sula, Honduras, has shown that the answer is “Yes!” Monte Verde has used biological control with predators of mosquito larvae to wipe out the mosquitoes and free its residents from the diseases.
Monte Verde’s main street during the rainy season.
Like many poor and neglected communities in Latin America, Monte Verde does not have a continuous piped water supply. In fact, the community’s makeshift water system delivers water (for household cleaning and cooking, but not for drinking) to each house for only a few hours each week. Every household must have a large number of water storage containers – such as small cement tanks (known as pilas), 50-gallon plastic drums, and 5-gallon buckets – in order to have water for the rest of the week, and these water storage containers are where the mosquitoes breed.
Water storage containers (from left to right): plastic tank (cisterna) with bleach bottle on top, cement tank (pila), white bucket (cubeta), plastic drum (baril). Clothes are washed on cement washboards like the one at the left side of the pila. The boy is a Monte Verde volunteer checking for mosquito larvae in the plastic drum.
For years, Aedes aegypti mosquitoes and dengue fever were a regular part of people’s lives. However, after suffering hundreds of cases of dengue, chikungunya, and Zika during 2014-2016, Monte Verde embarked in 2016 on an effort to eliminate the transmission of these diseases by getting rid of the mosquito. The project was facilitated by a small team from the nonprofit organization Operation Blessing Honduras.
Inspiration from Vietnam
Monte Verde’s inspiration for biological control came from Vietnam, which is the only place in the world known to have dealt effectively with the Aedes aegypti mosquito in recent decades. During the 1990s, 100,000-300,000 children in Vietnam were hospitalized each year with life-threatening Dengue Hemorrhagic Fever. Motivation was strong when the Vietnamese government developed a multi-method package for community-based Aedes aegypti and dengue eradication, launching a massive campaign in the mid-1990s to get the package into villages and urban neighborhoods across the nation. It took years to finish the job, but the results have been impressive. The mosquitoes and dengue fever have disappeared completely from northern Vietnam, and they are dramatically reduced in the rest of the country (see the full story about Vietnam’s eradication of the Aedes aegypti mosquito with biological control).
Tiny crustacean predators known as copepods are at the core of Vietnam’s Aedes aegypti eradication package. Despite their small size (less than 2 mm in length), copepods are like great white sharks for mosquito larvae (see a one-minute video of copepods in action against mosquito larvae).
Copepods are voracious predators of newly hatched mosquito larvae and other aquatic animals up to twice their size. This female copepod with egg sacs is about 1.5 millimeters in length.) Photo: Michael Brown.
Close-up of a copepod mouth, which takes in mosquito larvae like a wood chipper (see video). Photo: Michael Brown.
While common in aquatic habitats around the world, copepods don’t normally get into wells and water storage containers on their own. However, copepods collected from natural aquatic habitats can be cultured and introduced into water storage containers, where they multiply to such large numbers that they consume virtually every mosquito larva that hatches into the container. The copepods take care of themselves and survive in a container for as long as there is water. They don’t depend on mosquito larvae for their food supply because they eat a great variety of small aquatic animals in addition to mosquito larvae.
The biological control toolkit
Biological control is effective, environmentally friendly, and sustainable. It costs almost nothing except a heavy dose of community participation to ensure that every household does what is necessary for the biological control to work. Monte Verde’s strategy was to adapt Vietnam’s biological control strategy to the ecological and social conditions in Honduras.
The biological control in Monte Verde employed three different animals that prey on mosquito larvae:
- Copepods. A highly suitable copepod species (Mesocyclops longisetus) was found in a small marsh only a few hundred yards from the edge of Monte Verde. This species is common throughout Latin America, and because it is the largest copepod species, it is also the most effective predator. After setting up a culture of these copepods, Monte Verde could produce copepods by the thousands at virtually no cost. It was easy to introduce them to a variety of water storage containers around the community, and every container with copepods could serve as a source of copepods for other containers simply by transferring a bucket of water from one container to another. The copepods are particularly effective in wells, and they are equally effective at eliminating mosquito larvae from water storage containers, though they can be lost from a container when it is cleaned. More details about copepods for mosquito control.
- Baby turtles (Trachemys scripta). No larvae survive when a turtle is in a water storage container. A turtle can eat a thousand mosquito larvae every day. (See a one-minute video of a turtle in action against mosquito larvae.) If a turtle is in one container and larvae are spotted in another container, the turtle can be moved to clean out the larvae there. A baby turtle, costing about one US dollar, was provided to every house in Monte Verde that wanted to give it a try. Turtles become family pets and will live for years as long as they are fed a bit of tortilla, cabbage, or other household scraps to keep them healthy. Although it is known that pet turtles can sometimes be a source of salmonella infection for humans, research on the salmonella issue has established beyond doubt that turtles present no hazard to human health in water storage containers like those in Monte Verde. More details about turtles for mosquito control.
A baby turtle (Trachemys scripta) in a cement tank with cabbage provided as food. The turtles are family pets that live for years. They can be moved from one water storage container to another as needed.
- Tilapia fingerlings (Oreochromus niloticus). There is no mosquito production when these fish are in the water. (See a 30-second video of tilapia fingerlings in action against mosquito larvae.) With tilapia fingerlings available at very low cost (US$0.20/fingerling) from a Honduran government hatchery that produces them for aquaculture, the fish were distributed to all Monte Verde households that wanted them. At the same time that families used the fish for mosquito eradication, they could feed the fish household scraps to raise them as food.
Because it is never possible to achieve 100% coverage of water storage containers with biological control, it is reasonable to ask whether local mosquito eradication can be achieved under real-world conditions. The answer is “Yes” because of “egg sinks” that waste mosquito eggs. Egg sinks are the key to local mosquito eradication with biological control. When copepods, turtles, or fish are in a water storage container, the eggs that mosquitoes lay there are wasted because the larvae in those containers don’t survive to become mosquitoes. In fact, the transformation of potential mosquito breeding sites (e.g., pilas, drums, wells) into egg sinks is more effective than getting rid of the breeding sites. The practical rule is simple: “If at all possible, use biological control or some other method to transform a water storage container into an egg sink. If transformation is not possible, get rid of the container or replace it with a water storage container that can be transformed into an egg sink.” The experience in Vietnam has shown that a mosquito population collapses when enough breeding sites are transformed into egg sinks. Read more about egg sinks.
The Monte Verde project began in 2016 with educational meetings held by Operation Blessing Honduras staff to inform people about:
- The connection between the swarms of mosquitoes in their community and the small “bugs” (i.e., mosquito larvae) in their wells and water storage containers; and the connection between the mosquitoes and the large number of Zika, dengue, and chikungunya cases that they were suffering.
- How biological control could help to do something about it.
A very important outcome was the emergence of a core of approximately 10 community volunteers. These volunteers have been a key to success, working with their neighbors to put biological control into use at every house. They visit every household at least once a month to check for mosquito larvae and see how the mosquito eradication methods are being used. For monitoring purposes, a volunteer records the number of mosquito larvae or pupae that are seen and discusses with the family how to improve what it is doing.
Meeting of Monte Verde volunteers. The volunteers, mainly local housewives and mothers, include some men and boys as well.
The goal has been to ensure as much as possible that every water storage container in the community is covered by one or more of the biological control methods. It has been necessary to work out which forms of biological control are best for which kinds of containers. In other words, how can copepods, turtles, or fish be maintained long-term in different kinds of containers under actual conditions of water storage and water use? The diversity of the toolkit with copepods, turtles, and fish provides the scope to match the right kind of biological control to each kind of container and how the container is used by a particular family. The diversity is also able to provide choices to match the preferences that different families have for copepods, turtles, or fish. It is possible to employ more than one form of biological control for each container if a family wishes to do so, a redundancy that helps to ensure success.
It took more than a year of hard work and experimentation for the people of Monte Verde to flesh out the details for using biological control effectively, refine the process with the community, and craft the biological control into a sustainable solution. During this time, the mosquito eradication toolkit expanded beyond biological control to include measures such as getting rid of unnecessary water storage containers, replacing difficult-to-manage containers with containers more receptive to mosquito control, and the use of environmentally friendly larvicides to provide temporary, stopgap suppression of mosquito production when other methods were falling short. More information about the larvicides employed in Monte Verde.
The following is a brief description of how the toolkit has worked out:
- Wells. There are 142 backyard wells. Before the project began, they were “factories” producing thousands of mosquitoes each day. Copepods completely eliminated mosquito production from the wells. Copepods also proved to be the most effective way to prevent mosquito production from water in truck tires used to line the wells for structural support. For additional security, some families have chosen to add fish or a turtle to their well along with the copepods. A few wells have been sealed with concrete because they were no longer in use and had become highly polluted mosquito factories.
- Pilas and drums. Turtles proved most effective for pilas and drums. Copepods or fish can be lost when pilas or drums are cleaned, but this is no problem for turtles, which can easily be moved to another container during the cleaning. At first, there was a problem with turtles escaping, but families learned how to take care of their turtles so they would not escape. Some families have been able to prevent mosquito production in their drums by covering the drums with tight fitting lids to keep mosquitoes out, though mosquitoes can fly through even a small space between a lid and a drum.
- Buckets. There were 1849 buckets in Monte Verde at the beginning of the project. Buckets are not a practical place for long-term survival of copepods or fish because water is poured out of buckets so frequently. A campaign was mounted to get rid of unnecessary buckets and replace buckets with large plastic “cisterns” in which copepods can survive and prevent mosquito production. There are now 1147 buckets in Monte Verde. When not in use, buckets are stored so they don’t collect rainwater. If mosquito larvae are seen in a bucket, a household turtle can be moved to the bucket for a few hours to clean out the larvae, or the water (and larvae) can be poured into a pila containing a turtle that will eat the larvae.
The road to success
While there were numerous challenges and even serious setbacks during the first eighteen months of the project, the entire system was working smoothly enough by the beginning of 2018 for the mosquito population to decline month after month during the year. There is now no mosquito production whatsoever in Monte Verde’s wells and water storage containers, a striking contrast to the 43,218 larvae and pupae counted in Monte Verde’s water storage containers during a “snapshot” baseline survey in the middle of 2016 when the project began.
The number of water storage containers (pilas, drums, cisterns, buckets) observed to contain Aedes aegypti larvae during June 2016 to April 2019.
The impact on the diseases has been equally dramatic. There have been no recognizable cases of dengue fever or Zika in Monte Verde during 2017-2018, and the last chikungunya case was in April 2017.
Monte Verde volunteers with a sign declaring Monte Verde to be a dengue, Zika, and chikungunya free zone.
We are not personally aware of this kind of success eradicating the Aedes aegypti mosquito elsewhere in Latin America on any scale, large or small, since the collapse of DDT 40 years ago. Monte Verde’s success is an inspiration for thousands of similar communities to do the same. We don’t have to depend on high-cost solutions to get rid of the mosquito and the diseases at a local level. And it’s not necessary to wait for government. Local communities can do it for themselves if they just receive some help to get started.
The Monte Verde project is now ready for a new phase. The time has come to publicize the “Monte Verde model” and what it has accomplished, so biological control and its benefits can be offered to others. Monte Verde can serve as a demonstration site to show how to do it. It could also be a producer and provider of native copepods, native turtles, and tilapia fingerlings that other communities will need to embark on their own Aedes aegypti eradication.
The pivotal role of the volunteers in Monte Verde’s story highlights the importance of developing a strong team of volunteers at each new location. Monte Verde’s volunteers started out as ordinary residents of a mosquito-plagued community. Now they are citizen scientists with expertise in mosquito eradication by biological control and a commitment to continue improving the effectiveness and sustainability of the mosquito eradication toolkit for their community. The volunteers have developed a wealth of practical knowhow and experience with community organization for Aedes aegypti eradication. This ability will enable them to serve as “educators” assisting other communities with the necessary training. The consequence can be a cascade of local community empowerment for achieving a healthier life.
Ingredients for Success
What lessons does the Monte Verde story offer to help other communities free themselves from the diseases transmitted by Aedes aegypti? Why was Monte Verde so successful? What was the “lever” that propelled Monte Verde from being overrun with mosquitoes and disease to getting rid of both?
The “lever” had two major components:
- An appropriate and effective eco-technology. In the Monte Verde story, the eco-technology was biological control coupled with other methods that proved of practical use for preventing mosquito production in wells and water storage containers.
- The social organization to put the eco-technology effectively into use. Monte Verde volunteers were at the heart of that social organization.
The following “Ingredients for Success” are about what it takes for the eco-technology and social organization to be effective (see a full explanation of Ingredients for Success in environmental success stories):
- Outside stimulation and facilitation. Outsiders can be a source of fresh ideas. While action at the local level is essential, a success story typically begins when people or information from outside a community stimulate a shared awareness about a problem and introduce game-changing ideas for how to deal with it. The Monte Verde project began when Operation Blessing Honduras held community meetings to make people aware of the connections between:
- mosquito larvae in their wells and water storage containers,
- diseases transmitted by mosquitoes, and
- what they could do about it.
Operation Blessing did not give Monte Verde money, but it did provide two people to work full-time with the community.
- Shared community awareness and commitment. Strong democratic institutions and genuine community participation are prominent in success stories. Of particular importance is a shared understanding of the problem and what to do about it, and shared ownership of the action that follows. Communities move forward with their own decisions, manpower, and financial resources. Monte Verde’s shared understanding began with community meetings. That shared understanding developed greater depth among the volunteers as they proceeded with their work. The volunteers spread this understanding to their neighbors, whose understanding and commitment likewise deepened as they became active participants in the enterprise.
- Enduring commitment of local leadership. Trusted and persistent leaders inspire the deep-rooted and continuing community commitment and participation necessary for success. Monte Verde’s volunteers provided the joint leadership and persistence necessary for success. There were plenty of problems, but they overcame them. The volunteers developed a constructive working relationship with their neighbors. The volunteers are separate from Monte Verde’s community council, but they have maintained a close working relationship with the council.
- Co-adaption between social system and ecosystem. Social system and ecosystem fit together, functioning as a sustainable whole. Communities create a “social commons” to fit their “environmental commons.” The mosquitoes and diseases in Monte Verde were a negative part of its environmental commons. Mosquitoes breeding at one house could spread Zika, dengue, or chikungunya around the neighborhood. Monte Verde’s social commons for mosquito eradication was centered on the volunteers, who mobilized the community to manage the part of their environmental commons (i.e., wells and water storage containers) responsible for the disease problem.
- “Letting nature do the work.” In environmental success stories, people give nature the opportunity to marshal its self-organizing powers to set positive change in motion. Biological control is a “gift” from nature for low-cost and sustainable mosquito eradication. Turtles, copepods, and tilapia can work 24 hours a day to prevent mosquito production in wells and water storage containers. Once set up, these predators can continue to provide their service with no cash outlay and relatively little effort from people to maintain them. It is only necessary to provide suitable conditions for the predators to stay healthy.
- Rapid results. Quick “payback” helps to mobilize community commitment. Although it took more than a year for Monte Verde volunteers and their neighbors to work out the details for using their mosquito eradication toolkit, and another year to reduce mosquito production to zero, people were able to see tangible results soon after they introduced turtles, copepods, or fish into their wells and water storage containers. Mosquito larvae disappeared almost immediately from containers that contained a turtle, copepods, or fish. There was also a noticeable decline in the diseases within months after beginning the biological control. Once people saw that biological control really worked, they were more motivated to devote the attention and effort necessary to maintain copepods, turtles, fish, or some other method to prevent mosquito production in all of their water storage containers.
- A powerful symbol. It is common for prominent features of success stories to represent the process in a way that consolidates community commitment and mobilizes community action in an upward spiral of “success breeds success.” Success at locally eradicating the Aedes aegypti mosquito and its diseases has become a symbol embodied in a sign at the entrance to Monte Verde, proudly proclaiming Monte Verde to be free of the diseases. Another significant symbol for Monte Verde has been the installation of trash cleanup by the community. Pride in a clean community extends to pride in managing water storage containers to prevent mosquito production.
- Overcoming social obstacles. There can be numerous social obstacles to success. For example, competing demands for people’s time and attention. A key to achieving the necessary community participation in Monte Verde was strong personal connections between the volunteers and their neighbors, working face-to-face. Some households did not want to participate in the program. There were also “closed houses,” where owners or residents were seldom seen, and rooming houses that lacked the solid family structure that would normally take responsibility for managing water storage containers on the property. Persistence and “respectful assertiveness” were essential to secure involvement.
- Social and ecological diversity. Diversity provides more choices, and therefore more opportunities for good choices. The diversity of biological control methods (turtles, copepods, tilapia) provided the choices that each family needed to fit the right method to each of its containers. Social diversity came from Monte Verde residents, Operation Blessing Honduras, and a scientific advisor all working together. The volunteers also had to make full use of the diversity of ways that were acceptable for different families to prevent mosquito production at their homes.
- Social and ecological memory. Learning from the past adds to the diversity of choices, including choices that have proved sustainable by withstanding the “test of time.” Nature contains an evolutionary “memory” of its ecological design for sustainability. Operation Blessing’s previous experience working with communities in Honduras for safe water development was particularly helpful for it to facilitate community participation for biological control in Monte Verde. Because the scientific advisor had participated in Vietnam’s Aedes aegypti eradication program, he was able to share practical lessons from Vietnam about the biological control toolkit and community participation necessary for success.
- Building resilience.“Resilience” is the ability to continue functioning in the face of external disturbances that may be severe enough to set in motion far-reaching and undesirable changes. It’s about sustainability and sustaining gains in the face of future uncertainties. The key is adaptability. Another important part of resilience is to depend only on what can actually be depended upon. People in Monte Verde have very little money, but biological control is sustainable there because it doesn’t depend on money. Monte Verde has employed a strategy that depends on a resource that will continue to be available in the future, namely the time and attention of its residents. While Monte Verde has depended until now on facilitation from Operation Blessing Honduras, the volunteers are now strong enough to continue the project on their own. Their experience and confidence gives them the ability they need as “citizen scientists,” community organizers, and project managers to improve and sustain their Aedes aegypti eradication toolkit as new challenges arise. At the same time, continuing their connection with outside technical support will help the Monte Verde volunteers to remain strong.
Participants in this story
Xenia Caballero, Hilda Romero, and Arnulfo Larios (Operation Blessing Honduras) have worked with the Monte Verde community during the past three years. Gerry Marten has been the scientific advisor. Jacky Umaña, Dennis Salomon, and Nancy Echeverría of Operation Blessing Honduras also contributed to the project. The current Monte Verde volunteers are Magdalena Alvarado, Olga Bueso, María Carranza, Obed Cruz, Dunia Girón, Naelson Larios, Denis Lemus, Josselin López, Sarahí López, Melida Lozano, Norma Lozano, and Valeria Mejía. Past volunteers were Neptalí Alvarado, Manuel Castellanos, Alexis García, Bayron Lemus, Lurbin Lozano, Wilmer Mejía, Rubén Perdomo, Manuel Pineda, Anthony Ramírez, Ana Reyes, Patricia Rosales, José Santamaría, and Amada Ventura. Bill Horan (Operation Blessing International) was responsible for initiating the project and providing budget support. Brendan O’Leary contributed to monitoring and data analysis. Marco Suárez provided valuable advice during project planning. Eduardo Suárez provided copepod species identifications. Marlon López, Centro Nacional de Investigación Piscícola El Carao, Dirección General de Pesca y Acuicultura (DIJEPESCA), provided expert advice on the management of tilapia fingerlings. The Health Vigilance Unit, Cortes Regional Health Center provided valuable government cooperation. Philip Koehler and Roberto Peirera contributed pyroproxifen chips for testing in Monte Verde. Clarke donated Natular larvicide. The Clarke Cares Foundation and Vulcan contributed financial support. The New Orleans Mosquito, Termite and Rodent Control Board helped to educate Operation Blessing staff on the basics of mosquito control. Cynthia Harrison helped project staff to set up copepod cultures and provided instruction on mosquito monitoring methods.
Footnote on larvicides
Three larvicides, all of them completely harmless to people and pets, were tested in Monte Verde:
- Natular (spinosad) is an insect nerve toxin that decomposes rapidly in the environment. A Natular slow-release tablet reliably kills all mosquito larvae for about three weeks. This larvicide proved effective for regular use in the project.
- Vecto-bac (BTI – Bacillus thuringiensis) is a bacterial toxin highly specific to mosquito larvae and harmless to other animals. The liquid BTI formulation, which kills mosquito larvae for only a day, proved useful for occasional “one shot” elimination of mosquito larvae in water storage containers. Slow-release BTI “donuts” kill larvae for about two weeks and proved useful for temporarily eliminating mosquito production in polluted wells until the wells were put out of commission.
- Sumilarv (pyroproxifen) is an insect growth hormone that can prevent mosquito production for up to two months. A serious operational limitation for using Sumilarv in Monte Verde arose from the fact that pyroproxifen often does not prevent mosquito production by simply killing the larvae. It prevents mosquito production by obstructing the transformation of pupae into adult mosquitoes. As a consequence, if larvae were seen in a container after Sumilarv treatment, it was difficult to know for sure whether or not the pyroproxifen was actually preventing mosquito production. After testing Sumilarv for a variety of possible uses, Sumilarv has not become a part of Monte Verde’s toolkit.