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THE DEADLY BITE
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           Dr. Rakesh Sehgal, Dr. Abhishek Mewara, Dr. Taruna Kaura, Dr. Amit Sharma

                               Department of Medical Parasitology

          Postgraduate Institute of Medical Education and Research, Chandigarh, India

Part 1: https://www.youtube.com/watch?v=xRk0lSHst7g

Part 2: https://www.youtube.com/watch?v=JplhaaJ109w

More than half of the global population is at risk of mosquito bites. The seemingly innocuous, trivial sting of this tiny insect is capable of transmitting a number of disease-causing microorganisms and has a potential to cause parasitic diseases such as Malaria and Filariasis, viral diseases such as Yellow Fever, Dengue, Japanese Encephalitis, Chikungunya, West Nile Encephalitis, Eastern Equine Encephalitis, and bacterial disease such as Tularemia. These insects are not just pestiferous; they also affect the health of more than 500 million human beings and take more than a million lives each year, mostly in poorer developing countries including India.

Mosquitoes have been around on our planet for over 30 million years. They are widely distributed throughout the world and occupy diverse niches. The females of most species of the family Culicidae feed on blood of various kinds of animals and humans. The medically important species are mainly species of the genera Anopheles, Culex, Aedes, Mansonia, Armigeres etc. All mosquitoes need water for egg laying and larval development; some species are fresh water breeders whereas the others breed in dirty water. Anopheles larvae are mainly found in clean water, Culex prefers dirty stagnant water, rice fields, Aedes prefers to breed in artificial water collections such as in small containers, flower vases and water coolers used commonly in all houses, and Mansonia breeds on water plants. Mosquito species exhibit a specific rhythmic behaviour during their life cycles. A majority of species rest during the day time and their activity starts a little before the dusk and stops a little after the dawn. Anopheles and Culex species are night time biters, whereas Aedes and Armigeres bite during the day time also.

Mosquito control involves identification of the prevalent species of mosquitoes in a region, awareness of their changing habitat preference, the capacity to carry the disease causing microorganism and monitoring their population levels. For this, the Department of Medical Parasitology of PGIMER conducts continuous surveillance of the mosquito species and their breeding habitats in Chandigarh and its surrounding areas along with the NVBDCP (National Vector Borne Disease Control Programme, UT Administration, Chandigarh). The research workers place mosquito traps in various rural and urban areas of Chandigarh in evenings, nights and early mornings. The various species that have been present in Chandigarh during 2013 to 2015 are Anopheles annularis, An. culicifacies, An. stephensi, An. lindesayi, Culex tritaenorhynchus, Armigeres subalbatus and Aedes albopictus and Ae. aegypti from rural areas, and Cx. quinquefasciatus, Cx. tritaenorhynchus, and Ae. albopictus, Ae. aegypti and Ar. subalbatus from urban areas.

The government run programmes use various methods for vector control such as:

  • Indoor Residual Spray (IRS) of insecticides, use of chemicals that kill larvae in potable water,
  • aerosol space spray of insecticides,
  • malathion fogging during outbreaks,
  • use of larvivorous fish in ornamental tanks, fountains, etc
  • source reduction by filling of the open breeding places, and
  • channelizing water from the breeding source.

The most common method employed for the control of mosquitoes in various programmes is the use of insecticidal chemicals. However, due to the persistent use of these chemicals, many of the insects become resistant to the chemical and thus, become unmanageable. Moreover, overuse of the insecticides is also harmful for the ecosystem. Hence, there is a renewed interest in the use of natural chemicals like plants products such as neem extracts, turmeric extracts, eucalyptus oil, papaya seed extracts, etc., and biological agents like larvae-eating fish, crustaceans and frog tadpoles for vector control. In some preliminary studies in our department, we investigated the predation efficacy of frog tadpoles and crustaceans against mosquito larvae control in laboratory conditions and found them to be promising biological control tools, though further research is required for conclusive evidence. Fish are the most common larval predators used for biological vector control but it is difficult to use them in small ditches, puddles, rain-water pooled bodies, rice fields, etc. In such situations, frog tadpoles and crustaceans may be very useful; moreover, they are beneficial to the environment being harmless biological agents and essential parts of the food chain of the ecosystem.

Despite all the efforts of huge government-run programmes, mosquitoes are still a major public health problem. The nuisance of these pests can only be successfully curbed if there is active public participation that supplements the effort of the administration. We can protect ourselves, our family and society from acquiring the vector borne diseases by following extremely simple measures listed below. The measures are simple but worthwhile as the benefits they provide are enormous. The promising fact is that with a joint effort of the government, healthcare professionals and the public, it is entirely possible that these vector borne diseases can be controlled and eventually eliminated.

How you can avoid the deadly bite?

  • Remove left-over water from water-coolers at least once a week
  • Discard any water holding containers such as used tins, broken bottles and other artificial water collections
  • Cover the overhead water storage tanks and inspect them at least once every fortnight
  • Drain out stagnant water in and around your house
  • Encourage draining of stagnant water from any construction sites in your locality
  • Educate and encourage your neighbors too for not letting any water collected inside or outside their houses
  • Use small fish like Gambusia and Poecilia if you have any ornamental ponds or cisterns in your house or ponds in your farms
  • Use mosquito screens on windows and doors with at least 16 meshes per inch
  • Use bed nets and repellents while sleeping
  • Be aware of peak biting times of mosquitoes - Dengue and Chikungunya mosquitoes bite mainly from dawn to dusk, while Malaria and Japanese encephalitis mosquitoes bite mainly from dusk to dawn
  • Wear protective clothing such as long-sleeved shirts or kurtas, long pants, socks and closed shoes instead of open sandals
  • Use insect repellent creams or bands when you are at outdoors
  • Seek prompt medical help when suffering from fever of any kind

 

THE DEADLY BITE

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