Zika in Paradise: Learning from the Mosquito
This blog post is a collaboration of the “Team Zika & Water”: Karin Bremer, Maya Velis, Leslie Ford, Marieke Hagg, and mentor Tatiana Acevedo Guerrero.
The hum of mosquitoes can be heard around the world. From the forests of Uganda to the beaches of the pacific islands and the jungles of Brazil, mosquitoes have made their way into the homes and lives of billions of people. While many may consider these small insects a mere nuisance, a pest to be tolerated then forgotten, many others associate their delicate hum with a sense of trepidation. Despite their small size mosquitoes can create big problems for humans. Yellow Fever, Dengue, Chikungunya, and Zika are just a few of the well-known mosquito borne diseases that are transmitted by the aedes agyepti mosquito, a well-studied and wide spread variety.
The aedes agypti has most recently been on the tip of the tongue for news reporters, politicians, and scientists because of the role they played in the 2016 Zika pandemic in the Americas. While the outbreak has officially been declared over active transmission of the virus is still occurring in many Latin American countries. One such country is Colombia, where the second highest number of cases, after Brazil, was reported (65,000 cases). The highest incidence rate in Colombia was on the island of San Andrés which is located in the Colombian Caribbean.
San Andrés has been advertised as a ‘Paradise’ for adventure seekers and tourists looking to experience the unique blend of Colombian and Creole culture found on the island. But under the iconic beach scenes, swaying palm trees, and coral reefs captured in the vacation photos of nearly 700,000 tourists annually, another visitor to the island has found a paradise. The abundant potholes, building materials, and water storage containers that riddle the middle and southern parts of the island, beyond the view of the tourism industry thriving on the North Shore, have long been the home of the aedes agypti mosquito. The occasional case of Dengue or Chikungunya was grudgingly tolerated but the introduction of Zika virus, and the potential birth defects that can come from the disease, changed the islander’s perspective.
In response to the outbreak the Colombian government, and agencies like the World Health Organization, tried to tackle the giant of the Zika pandemic by focusing on short term solutions such as preventing mosquito bites and eliminating mosquitoes. Among their strategies to accomplish this task was the elimination of stored water, which was identified as the main breeding site of the aedes agyepti mosquito on San Andrés. This solution, however, met with little compliance on the island where there is a shortage of drinking water as a result of over population, climate change, and poor water distribution. In April of 2016, simultaneous to the Zika outbreak, protests broke out on the island because minority communities in the central region had not received piped water supply for more than 40 days. This shortage occurred mainly in the poor minority communities of the or ‘Root’ (raizal) people of the island.
This situation raised the question ‘How can rainwater be stored safely on San Andrés, while minimizing the risk of Zika?’ A team of young water professionals decided to tackle this question as part of the IHP-IWRP ‘Climate Change, Migration, and Me’ Challenge. The case was proposed by IHE Delft Water Management MSc candidate Leslie Ford and the team was mentored by Lecturer Tatiana Acevedo Guerrero. Per the challenge requirements the team looked at solutions to mitigate the impact of climate change and migration on the island that were cost effective, feasible, and sustainable. Interventions proposed by the team considered the existing islander culture of rainwater harvesting and focused on small scale solutions to address their water storage challenges that could be easily implemented at the household level by individuals using materials readily available on the island and technology that is easy to replicate. Unlike interventions taken before, these solutions focused not on eliminating the breeding sites but instead on studying the behavior of the mosquito and making small changes to the water that prevent the big problem of aedes agyepti breeding in it. Based on extensive literature review the team targeted three characteristics of water that make it suitable for mosquito breeding: temperature, access, and movement.
In order for the aedes agyepti mosquito to breed in water it must have a temperature above 18 degrees Celsius. Optimal breeding occurs around 26 degrees Celsius, which is close to the average temperature of San Andrés (27 degrees Celsius). To prevent mosquitos from breeding in water stored within the household the use of clay pots is recommended. Clay is widely available on San Andrés and due to evaporative cooling clay pots can cool water up to 7 degrees Celsius from the ambient air temperature. If these clay pots are stored inside or in shaded areas where the ambient temperature is lower than the level of cooling on an average day in San Andrés would be sufficient to prevent mosquito breeding. Further cooling could be achieved by storing the pots underground. To further prevent mosquitos from accessing the water readily available mosquito nets can be placed over the openings of the pots.
For mosquitos to breed in water they must first have access to the water. Unfortunately, only a thin film (4 mm) of clean, warm, standing water is needed for the aedes agyepti to breed. Within one batch an aedes agyepti can lay up to 100 eggs. This makes the potential for reproduction staggering. An old bottle cap, discarded plastic, old tires, or concreate blocks can all become potential breeding sites. To eliminate this possibility building sheds over stored building or recyclable materials is recommended. With the shed not only are stored items protected but there is also the potential for increased rainwater harvesting. Through incorporating a safe mosquito proof water storage container and a soak pit to allow all excess water to infiltrate into the ground more water can be harvested and additional breeding sites from puddles around the shed can be eliminated. Additionally, the soak pit helps to prevent runoff in heavy rainfall events which improves the aquifer recharge.
Water must be still in order for mosquitoes to breed in it. This means that even a small movement in the water can prevent mosquito breeding. For larger bodies of water that cannot be covered or cooled, for example small ponds for watering animals, small windmills are recommended. These windmills will create movement on the surface of the water by transferring the rotation of the blades to paddles located just below the surface. These windmills can be built from recyclable materials cheaply available on the island such as a discarded bike wheel, repurposed tin roofing, and used pipes. The windmill also has the added benefit of providing aeration for water bodies that could make them suitable for fish which would further reduce the presence of mosquito larvae.
To ensure that these solutions are feasible and sustainable a community action group should be created under the supervision of an existing NGO on the island that is already well connected with the islanders. This will allow the local people to provide input into the design and implementation of the solutions and provide a platform for peer to peer learning. This method will also ensure that the solutions are reaching their target audience of households.
These solutions were presented by the team on Wednesday November 1st, at the Amsterdam International Water Week during the finals of the ‘Climate Change, Migration, and Me’ challenge where the team won the popular vote. Also the official jury, consisting of Jan Busstra (Head of Unit Marine and International Water Policy – Ministry of Infrastructure and Water Management); Marcel Beukeboom (Climate Envoy of the Netherlands), Louise van Schaik (Head Clingendael Sustainability & Senior Research Fellow) gave the team the overall grand prize of the challenge, a trip to the COP23 UN Climate Change Conference in Bonn, Germany where the results were also presented.