An increase in dengue cases, which is likely to be related to climate change, threatens rural Cambodians’ health and welfare. The keeping of Guppy Fish has emerged as a sustainable and cost-effective response.
In recent years, Cambodia has seen an increase in dengue cases – a trend which may be related to climate change. With almost 15,000 cases reported in 2015 alone, dengue has become a serious concern to both public health and economic development in Cambodia: 65% of the affected households fall into debt after paying for the necessary treatment and many work days are lost to the disease. For these reasons, controlling dengue is one of the objectives of Cambodia’s health and climate change strategy.
Dengue is caused by the dengue virus, which is primarily carried and transmitted by the Aedes egypti mosquito. In the absence of a cure or vaccine, the best methods for fighting dengue are vector control (i.e. the reduction of mosquitos) and protection against mosquito bites (e.g. screens on windows and doors). A recent study, however, indicates that in many areas of Cambodia mosquitos have become resistant to some of the substances used for vector control, pointing to the need for a new, more sustainable approach to mosquito reduction.
Testing Guppy Fish as part of an integrated vector management strategyIn 2006, a small WHO-supported field trial demonstrated that Guppy Fish – or seven-coloured fish, as they are called in Khmer – could provide a natural alternative to costly and potentially harmful insecticides. Guppies eat the mosquito larvae, which thrive in stagnant water, before they can develop into adult mosquitos and transmit the dengue virus. Together with Cambodian National Center for Parasitology, Entomology and Malaria Control and WHO, the Malaria Consortium set up a research project to assess the efficacy and acceptability of Guppy Fish as part of an integrated vector control strategy for rural Cambodia. It ran from August 2014 to November 2016 with financial support from Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH, on behalf of the German Federal Ministry for Economic Cooperation and Development, and UK AID.
Guppy Fish were placed in household water containers to control mosquitos
The project was implemented in 31 villages in Kampong Cham, a province with one of the highest dengue incidence rates in Cambodia. It compared three groups of households: The first received dengue-related health education as well as Guppy Fish for large household water containers and, for smaller water containers in which Guppy Fish cannot live, the hormone pyriproxyfen (PPF), which prevents larvae from developing into mature mosquitos. The second group received health education and Guppy Fish only, and the third group – the control – did not receive any interventions.
Community health structures formed the bedrock of the project. A breeding site for guppies was established at the local health centre. From there, community health volunteers collected the 3-4 centimetre-long fish in buckets and distributed them in their villages. Guppy Fish were placed in large water containers (> 50 litres) for cooking and cleaning, which are usually kept near homes and attract the majority of mosquitos that carry dengue. Volunteers also conducted regular monitoring visits and health information sessions. “I bring the fish to the homes of the people in my village,” explains Ven Channy, a community volunteer. “Each month, I check twice if the fish are still there. Before giving people their guppies, I tell them what they are for. I explain that the fish will not harm their health. They can eat a lot of mosquito larvae so they won’t have any more mosquitos, and no dengue either.”
The community-centred communication strategy increased acceptance and behaviour change
Gaining the communities’ acceptance was vital for this approach to succeed. Community members needed to keep guppies and small plastic disks which release the PPF in the water containers and practise additional preventive behaviours, like avoiding mosquito bites and conducting regular village clean-ups to minimise mosquito breeding sites. In addition to information sessions, the project used flyers, banners and tuk-tuks (small three-wheeled vehicles), which travelled through the villages broadcasting educational songs, to disseminate relevant health messages. Respected community members, like monks and teachers, helped to share important health messages, which enhanced the project’s credibility and community members’ willingness to adapt the recommended behaviours.
The local communities’ concerns were taken seriously throughout: “In the beginning, some people in the villages were afraid that the PPF might be harmful to their health,” remembers John Hustedt, the project manager. “However, we were able to overcome much of the initial resistance by increasing the quality and number of our community health education sessions. It was important to listen to the issues which the health volunteers communicated to our team and address them.”
The integrated approach reduced the number of mosquitos by half
Over the course of the project, village health volunteers conducted over 2,300 health education sessions in the villages and around 5,700 additional individual sessions at household level. As a result, positive attitudes toward dengue prevention measures increased significantly. By the end of the project almost all households had accepted the control measures. This led to a reduction of mosquitos by about half – quite an achievement for a simple, cost-effective, community-based solution. The data suggest, however, that adding PPF in the smaller containers had less added value in reducing mosquitos than expected. Nonetheless, Dr. Hay Ra, the deputy director of the Kampong Cham Department of Health, was very satisfied with the project results. “We have noticed that areas with Guppy Fish have fewer cases of dengue than areas without Guppy Fish,” he says.
The project results will inform the national dengue control strategy
The project has shown that keeping Guppy Fish in large household water containers, as part of an integrated approach that also promotes other preventive measures, is an effective and low-cost dengue control method that is acceptable and sustainable in the Cambodian context. These findings will inform the further development of Cambodia’s national dengue strategy.