Tag Archives: dengue

Targeting mosquito larvae through Integrated Vector Management

Malaria Consortium is piloting a project on integrated vector management to assess the effectiveness of various control strategies to prevent the transmission of dengue. The study is being conducted in Kampong Cham province, Cambodia and is funded by the Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH commissioned by the Federal Ministry for Economic Cooperation and Development (BMZ) and UK aid from the UK government.

There has been a marked rise in dengue in the country during 2015. According to a recent  National Malaria Center report, health workers recorded 12,218 cases during the first 41 weeks of 2015. This is an increase of 9,284 compared to the same period in 2014.

Kampong Cham is one of the high-risk provinces, recording several dengue outbreaks in recent years. Cases can skyrocket, especially during the rainy season, where the environment provides mosquitos with more breeding sites and human movements play a major role in the spread of the disease.

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A sample adult mosquito was analysed in the laboratory. Species identification was made using a compound microscope.

“We have tripled the number of cases this year,” said Dr Hay Ra, Dengue Supervisor in Kampong Cham province. “So far, we have recorded 1,556 dengue cases including eight deaths. The most at-risk group is the population under age 15. The high density of population and climate change contributes substantially to these dengue epidemics. This area has high density of population of approximately 200 people per square metre. The rainy season also has changed – last year we had the rainy season start from April and last for seven months, while this year it started in July.”

“In this region the average flight distance for mosquitoes is about 100-200 metres,” explained John Hustedt, Malaria Consortium’s Senior Technical Officer who is leading the project. “In highly dense areas, mosquitoes can spread around the disease more widely as mosquitoes can bite more people in one area.”

At the health centre near the Ou Svay Commune, 20 of the 500 litre water jars containing various colourful guppy fish have been set up. Guppy fish have been used to reduce the mosquito larvae and this place is known by the village health volunteers as ‘the guppy fish bank’ where they can come to collect the guppy fish and provide it to the villagers. It has been under the supervision of the Health Centre Chief, Jeng Meng Hong. “We are responsible for two communes and 20 villages and each village has two health volunteers,” he explained. “So we have about 40 health volunteers who will visit our health centre and collect the fish. Each month, we have a monthly meeting to ensure all their assigned households have guppies in all large containers, and replace them if necessary.”

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Malaria Consortium’s staff inspected the number and condition of guppy fish in water jars at the village health volunteer household.

The fish collected from the guppy bank will be allocated to each household and released in their large water containers. It has been found in previous projects to be effective and acceptable by the local villagers.

Muchh Kounthea is one of the villagers who adopted the practice. The 56 year-old farmer has seven jars in her house, five of which contain the guppies. “I am fine with these fish. I just hope we do not have dengue in the village,” she said. Although she has never had dengue before, she knows about it and can recognise the period of dengue outbreaks. “Dengue usually occurs during rainy season around May to October. I know one child who got really sick because of dengue and had to seek the treatment at the private referral hospital.”

Although there is evidence suggesting the use of guppy fish can be beneficial in dengue vector control, no cluster randomised trials to evaluate their effectiveness nor a proper evaluation of their impact on adult mosquito densities have been conducted.

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Guppy fish are bred and nurtured at the guppy bank at the health centre.

To understand and evaluate the impact of a guppy fish and a combination of new vector control tools to sustainably reduce the Aedes mosquitoes, Malaria Consortium’s pilot project also implemented an entomological survey in the villages. In cooperation with the National Dengue Control Programme (NDCP), the entomological team was deployed to collect larvae, pupae, and adult mosquitoes from the targeted villages. All containers around selected houses were inspected and all samples were taken to the laboratory for further analyses. The survey received a lot of attention from the villagers.

At the same time, a survey on the knowledge, attitudes, and practices surrounding water use and vector-borne disease prevention was also conducted. This separate survey aims to guide and evaluate communication and behaviour change interventions to reduce dengue transmission.

Following the survey, training in behaviour change communication and health education was provided for the community health workers. The vector control intervention started in late November will last a year until the same period in 2016.

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Sample larvae and pupae were collected during the entomological survey.

Wanweena Tangsathianraphap is External Communications Officer for Asia