Southern States - Kerala-Thiruvananthapuram   

Campaign launched against mosquito-borne diseases

By Our Staff Reporter

THIRUVANANTHAPURAM Nov. 24. The district health authorities on Monday launched a campaign to popularise the inexpensive and eco-friendly method of cultivating fish varieties that feed on the larvae of mosquitoes as part of measures to tackle the scourges of dengue, malaria encephalitis and filaria.

According to the action-plan, fish hatcheries would be set up at all the 19 Public Health Centres (PHC) and 65 mini PHCs to cultivate the Guppy variety of fish which have a well-known appetite for mosquito larvae.

Schools of fish would be released into wells and other water bodies, which are breeding sites of various mosquito species, which are vectors for dengue, malaria and Japanese Encephalitis. In fact, studies have shown that several areas in the city have high density of vector mosquitoes for these commonly occurring diseases.

The larvicidal programme would involve construction of cement tanks in each block PHC/CHC, identification of distribution tanks in each mini PHC, rearing Guppies at the block PHC/CHC levels and releasing the shoals from peripheral tanks to selected water bodies.

``These fish play an important larvicidal role in a long-term biological control of vector mosquitoes,'' says the district medical officer, E. K. Madhavan.

In fact, the controlled multiplication of Guppy fish in wells and water bodies at Valiathura is said to have played a significant role during the outbreak of malaria at Valiathura in 1997, which led to ten deaths and several thousands of people falling sick. The advantage of the Guppy is its ability to survive in all types of water bodies and tolerate high degree of pollution with organic matter. The optimum temperature is between 24 degree C and 34 degrees C and pH value in the range between 7 and 9.

Already, the health department operates fish hatcheries at 19 PHCs in the district. According to official figures, 476 shoals of fish were introduced at 241 sites as biological control of mosquitoes taking the aggregate of shoals deployed this year in larvicidal operations to 7456 at 2535 spots in the district.

It is estimated that an adult fish feeds on between 80 and 100 larvae a day. The methodology is also inexpensive and eco-friendly as it substitutes, to an extent, the unleashing of chemical sprays on water bodies.

The use of larvivorous fishes as an important mosquito control measure dates back as early as to the 1930s. Moreover, the technique of releasing shoals of Guppy fishes into larvae- infested water bodies represents a simple, sustainable and eco- friendly measure.

In comparison, chemical warfare against vectors carries an environmental risk and as a short-term source reduction (deprivation of breeding site) measure could even lead to the species developing resistance.

A major component of the campaign would be to popularise the concept among the community. An exhibition on Guppy varieties, breeding habits and larvicidal role, was organised at Valiathura where the scheme was formally launched.

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