Controlling Mosquitoes

Mosquito control is very important part of mosquito-borne diseases control strategy, although elimination of diseases in an area does not require the elimination of all mosquitoes. Socio-economic improvements (houses with screened windows, air conditioning, etc.) combined with vector reduction efforts and effective treatment have led to the elimination of mosquito-borne diseases without the complete elimination of the vectors. On the other hand, controlling these highly adapted, flying and hiding vectors is indeed a formidable task. Development of resistance to insecticides has compounded the problem. However, the use of non-biodegradable and non-eco-friendly insecticides like DDT also should be replaced with safer methods in order to avoid their harmful effects.

Mosquito breeding

About 50-200 eggs are laid per oviposition on the surface of stagnant water and these eggs develop into adult mosquitoes in a span of about 5-14 days, passing through the stages of larvae and pupae. High humidity and ambient temperature between 20-30º C provide ideal conditions for breeding of mosquitoes. Common sites of breeding for mosquitoes include rainwater pools and puddles, borrow pits, river bed pools, irrigation channels, seepages, rice fields, wells, pond margins, sluggish streams with sandy margins, hoof prints, tyre tracks etc. Water stagnation due to construction of dams, reforestation, shrimp farming, fish ponds etc., have also been identified as possible sites of mosquito breeding. They make use of man-made sites such as building-construction sites, wells, garden ponds, reservoir, overhead tanks, ground level cement tanks, water coolers, tyres, barrels and tins, intra-domestic containers etc.

Mosquito control

Every step taken to control the mosquitoes has a cumulative effect and contributes immensely to control the diseases. Source reduction involves preventing development of mosquito larvae. The female mosquitoes need a blood meal from a vertebrate host to nourish their eggs. By personal protection against mosquito bites, this blood meal can be denied, leading to reduction in mosquito eggs and hence mosquito population. Personal protection includes closure of windows and doors to prevent entry; protection of humans by covering the body with clothes and use of mosquito nets and organic mosquito repellents will further help in preventing mosquito bites.

Female mosquitoes lay the eggs on water collections where they develop further over a week into adult mosquitoes. By preventing water logging, destroying unwanted water collections and keeping the water containers closed, sources of egg laying can be denied and breeding of mosquitoes can be prevented. Further, different types of biological (Guppy or Gambusia fish or bacteria or fungii) larvicides can be used on such breeding grounds to kill the developing larvae and pupae.

It is far easier to kill the non-flying forms of the mosquitoes than going after the adults that can fly a kilometer or more. The adult mosquitoes can live up to 4-10 weeks depending on the ambient temperature and humidity. Space sprays are used to instantly kill the adults and residual sprays, on their resting places such as walls, are used for residual mosquitocidal effect. But most of such insecticides have effects on the human beings as well as the environment and other life forms. So, preparing organic compounds as mosquito repellent is the ideal choice.

The adult mosquitoes enter the human dwellings between 5 pm-10 pm and early morning and hide in dark corners, to come out and bite human beings at night, mostly between 11 pm-4 am. The entry of the adult mosquitoes can be prevented by keeping the doors and windows closed between 5 pm-10 pm and early morning. Screening of all the windows and vents is a very easy and sure method of controlling the entry of adult mosquitoes. The hiding places of the mosquitoes, such as clothes hanging in the open, can be minimised. All these in turn will deny the blood meal and development of eggs.

The easiest, cheapest and most environment-friendly method of mosquito control is preventing the mosquito from laying eggs and preventing the development of the eggs into adult mosquitoes, by reducing the sources of breeding. These anti-larval measures are not only simple and cost effective, but also environment friendly. This is done by avoiding or eliminating both the clean and dirty water collections, which are artificial, temporary and man made.
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