Thursday, April 26, 2018

There has been a paradigm shift in the behavior of Aedes mosquitoes

Over the past years, there has been a paradigm shift in Aedes mosquitoes, which cause dengue fever.

Traditionally, Aedes aegypti has been regarded as a day biter and one which breeds indoors and also bites inside the house. This perception no longer holds true.

Then - It bites only in the day.
Now - It bites in the light. Day and night does not matter.

Then - It breeds in safe water.
Now - It breeds in stagnant water from natural sources.

Then - It breeds only inside the house.
Now - It breeds both inside and outside the house, in any discarded objects/containers with stagnant rainy water collection.

Then - Mosquito breeds in water tanks on the roof and coolers.
Now - It breeds both in small and large water collections. It can even grow in the caps of bottled water.

Earlier, a temperature ranging between 30oC and 32oC was considered as the optimal temperature for Aedes mosquito breeding. But, now this range has been lowered to between 24oC and 28oC.

The use of air conditioners (ACs) in homes generally coincides with the arrival of summer. ACs are usually set at a temperature of 24oC, now an ideal temperature for the Aedes mosquito to breed and also survive all through the year. The extrinsic incubation period of the dengue virus is also reduced i.e. decrease in the time required for the virus to replicate and disseminate in the mosquito. The result is an increase in disease transmission rate. Aedes eggs can survive in a dry state for at least a year.

Hospitals have central air conditioning. It is important to check for mosquito breeding sites in central ACs in hospitals and also in homes.

The mosquito cannot comprehend the difference between day and night, or indoor and outdoor. It is the environment that counts. The climate is changing, so is the behavior of mosquitoes and so is the epidemiology of the disease they cause. Earlier prevalent as a monsoon disease, dengue is now reported all through the year.

Dr KK Aggarwal
Padma Shri Awardee
Vice President CMAAO
Group Editor-in-Chief IJCP Publications
President Heart Care Foundation of India
Immediate Past National President IMA

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