Biological warfare against mosquitos

The Colombo Municipal Council (CMC) is using biological weapons such as larvivorous fish and bacteria to help eradicate dengue.

The CMC has begun breeding mosquito larvae-eating fish such as mosquito fish (Gambusia affinis), guppies, (Poecilia reticulata), nala handaya (Aplochcheilus dayi) and thithaya (Puntius titteya) to be put into irrigations tanks and canals.

“The fish are bred in the council’s pest control centre and we are planning to introduce them into manmade waterways,” CMC Chief Medi- cal Officer Dr. Ruwan Wijayamuni said.

The council is also employing Bacillus thuringiensis israelensis, bacteria developed in Israel that is fatal to mosquito larvae when the larvae feed on it.

Dr. Wijayamuni said the bacteria had been introduced last year by the Health Ministry and used in parks including Viharamahadevi Park, pools, concrete slabs, canals and other irrigations. The bacteria are known to be safe for humans, animals and all but a few insects.

The CMC is using an American product named Mosquito Dunks, a hardened form of the bacteria, that kills mosquito larvae without adverse effects on the public. The cubes dissolve in water.

“We will use dunks on all water sources excluding drinking water,” Dr. Wijayamuni said.

The CMC had purchased 10, 000 dunks last year and planned to double or treble that purchase at a cost of Rs. 5 million this year.

Dr. Wijayamuni said that although dengue cases had dropped this month a rise was expected in April-May and he warned people to keep their homes clear of dengue breeding places. He said 583 suspected cases of dengue had been reported in the past 45 days, 80 per cent of whom would be diagnosed with the illness