LAHORE, Sept 29: Fumigation and sprays are not permanent solution to control mosquitoes as the insect develops after sometime resistance against the chemicals used in the methods.

Spread of epidemics like dengue could only be prevented through bio-control methods or by using natural enemies to manage mosquito population with a minimum risk to humans, wildlife and the environment, said GCU Zoology Department Chairperson Prof Dr Nusrat Jahan at a seminar on ‘prevention and control of dengue fever’ arranged for the faculty members on the campus on Thursday.

“The use of biological agents includes predatory insects and other invertebrates like copepods, parasitic nematodes, larvivorous fish and microbial entomopathogens, including bacillus thuringiensis. Different formulations of these biological insecticides are commercially available, and due to their environmental safety and specificity to nematoceran diptera (including mosquitoes) have become mosquito control agents of choice almost throughout the world,” said Prof Jahan.

She said after the first outbreak of dengue, a research was started at the GCU using many biological control agents and results were evaluated on the base of lethal concentrations, percentage larval mortalities and pupae or adult emergence both in laboratory and field bioassays.“At present, we are in the process of detecting dengue viruses in vector mosquitoes which will act as an early warning tool for the control of dengue in the country,” said Prof Jahan while stressing the need for supporting the research in the area of medical entomology for developing population management strategies of dengue vectors in Pakistan.

She also emphasised the use of ‘lethal ovi-traps’ in houses and other places to control mosquito population. “An ovi-trap can be made through a black plastic container filled with water containing a thin paddle of wood. The ovi-trap could be made lethal for mosquitoes by using chemical or biological insecticides,” she said.

The use of small crustaceans known as copepods; two species identified recently in vector biology laboratory as “Mesocyclops” when mixed with Bti were found highly successful (100 per cent) to control first instars Aedes larvae in large ornamental pounds or in other containers with large volume of water.

“At present, the situation is really alarming as in the last two decades dengue cases have been increased nearly four times globally. The first outbreak of dengue fever was reported from Karachi in 1994 in Pakistan,” she said and urged students and teachers to develop a habit of emptying and cleaning water storage containers, gutters, flower vases and desert coolers, proper disposal of discarded containers and tyres; removal of ornamental or wild plants that collect water in the leaf axils. She said non-biodegradable items of household, community and industrial waste, non-essential or discarded containers should be properly disposed of regularly.

GCU Vice-Chancellor Prof Dr Khaleequr Rahman said the university would support the research being conducted by the Zoology Department on biological control of dengue fever.

He said the GCU had been using the best available chemicals for fumigation not only on the campus but also in surrounding areas. Designed by the varsity, posters were being distributed among masses to raise awareness about dengue fever and its prevention.