Mosquitoes may reach indoors to find warmer places

October 21, 2019

Islamabad : The activity of mosquitoes including ‘aedes aegypti’, the vector that causes dengue fever is decreased outside usually after the second week of October as they are not able...

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Islamabad : The activity of mosquitoes including ‘aedes aegypti’, the vector that causes dengue fever is decreased outside usually after the second week of October as they are not able to bite because of weak energy in joints due to fall in temperature that do not let them make a firm grip and mount on the body of a person while sucking blood. Therefore they would be at this point in time trying to reach comparatively warmer places that are available inside homes, offices, vehicles like buses, vans, cars and rail compartments to rest and bite.

Mosquitoes may move indoors or in other words in the bedrooms and kitchen where they can rest in corners behind the curtains or furniture to rest and bite and lay eggs to hatch.

The data of previous years provides us statistical evidence and information that reporting of dengue fever patients shall meet a decline after the second week of October and the outbreak of the infection shall most probably meet its end in the month of November or so. The nature helps by fall in temperature enabling the epidemiologists to conclude that the current spell of dengue fever would further decrease in terms of morbidity in next three to four weeks.

Epidemiologist Dr Muhammad Najeeb Durrani who is Member Global Outbreak Alert and Response Network (GOARN) expressed this while talking to ‘The News’ on fall in temperature and its effects on the on-going dengue fever outbreak in the region.

This year the disease has been comparatively much stronger with respect to previous years, excessive rains are attributed to be one reason, and introduction of a new strain of dengue virus could be another very important reason to which the local community was not immune, but this fact needs to be investigated by genotyping of the current outbreak strains of dengue virus, the samples are to be obtained from the affected people in different Union Councils of Islamabad, said Dr. Durrani, former District Health Officer Islamabad.

He added the epidemic is still on-going and not controlled till the moment and the sharp rise in number of cases in the current year with greater mortality rate is the fact that is showing typical dengue fever pattern that fluctuates from year to year.

He said the current trend of decline to some extent in the twin cities of Islamabad and Rawalpindi is due to the fall in temperature in this part of the country unlike Lahore and Karachi where the disease is still affecting scores of people at almost the same pace as was witnessed in the month of September due to just comparatively slight drop in temperature that the mosquitoes can resist.

It is important that as per scientific research, the mean threshold temperature was determined to be 13.8 degree centigrade which is critical temperature to limit the activity of ‘aedes aegypti’. Epidemiologically as low as 13.8 degree centigrade is considered to be critical temperature for mosquitoes’ larvae and it may result in disappearance of the dengue fever vector.

According to Dr. Durrani, the biting ability and physiological functions of ‘aedes aegypti’ are affected by the fall in temperature particularly below 13.8 degree centigrade. The mercury has already started falling in the twin cities of Islamabad and Rawalpindi and their surroundings that hints that the severe dengue fever outbreak in the region would be under control within next three to four weeks.

The existing adult ‘aedes aegypti’ in the environment, however, may continue transmission of the infection but its rate would most probably be decreasing within next two weeks or so depending on fall in mercury.

This is high time for insecticide residual spray to be carried out inside homes and to make last efforts religiously in identifying active breeding sites and destroying them and concentrating on solid waste disposal so that the adult female mosquitoes may be killed and would not be able to lay eggs to hatch in the next summer season, said Dr. Durrani.

He added another few things to be noted for the future control of the disease are the migration of the virus from the endemic areas that put local population at the ever increasing risk of contracting the deadly disease, the vector control, solid waste disposal and public awareness and liaison among all stakeholders for dengue prevention, control and mitigation.

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