Mosquito density, particularly that of dengue-causing vector Aedes aegypti, is high in parts of North Chennai, an entomological survey has found.
The survey, undertaken by the Indian Public Health Association’s Tamil Nadu chapter, found that there was “unexpected” mosquito density in parts of northern Chennai, including Tondiarpet, Washermanpet, Royapuram and Tiruvottiyur. The survey also found that the density was low in many parts of South Chennai — Saidapet, Anna Nagar, Adyar and Besant Nagar — with Thoraipakkam and Madipakkam being exceptions, S. Elango, president of IPHA’s Tamil Nadu chapter, said.
“Our entomological survey has been going on since February this year. However, we found a rise in mosquito density only from June 15. An interesting aspect was that we found more Aedes aegypti, the dengue-vector, and not Anopheles, the malaria vector. Nearly 10 years ago, the breeding of Anopheles was more in the city. This was the reason why earlier 60-75% of malaria cases in Tamil Nadu were from Chennai,” he explained.
A change in the breeding pattern of Aedes aegypti was also noticed during the survey, he said. “Usually, the Aedes breeds in water collected in small containers, such as plastic cups and coconut shells.
Now, like Anopheles, we found the Aedes breeding in bigger sources such as overhead tanks and low-level sumps. It looks like the Aedes has encroached on the breeding source of the Anopheles, and this needs to be studied,” he added. The team found that the overall mosquito density was high between 6 p.m. and 8 p.m., and that mosquitoes, including the Armigeres, swarmed into households.
In fact, during the survey, the IPHA’s entomology wing found plenty of breeding sources near railway stations and in State government buildings, said Dr. Elango, who was formerly the Director of Public Health. “The railways’ sanitation and public health wing concentrates on keeping railway stations clean, but the surrounding areas are missed out. We found several plastic cups, bottles and other containers that had turned into breeding sources,” he said.
The Southern Railways should coordinate with the State government, to take up vector control measures, he said.
The condition of several State government buildings, maintained by the Public Works Department was also bad. The need of the hour, he said, was a permanent plan for dengue prevention. “The Chennai Corporation should strengthen its zonal entomological teams and take up intensive vector control activities. More field assistants and mazdoors should be engaged toprevent dengue, in the coming months,” he added.
