Mosquitoes simply cannot be wished away. Like the human race, the mosquito wants to ensure its survival through successive progeny. It is now considered one of the most dangerous creatures due to its ability to spread diseases, says Maharashtra’s surveillance officer Dr Pradip Awate.
This blood-sucker has been increasing manifold: the Centre for Disease Control (CDC), Atlanta estimates that annually the mosquito bites more than 700 million people. No longer an irritating nuisance, these tiny creatures have caused millions of deaths worldwide. Closer home as many as 11,26,661 cases of malaria were identified with 287 deaths in the country in 2015. Dengue took 200 lives and infected as many as 97,740 persons according to the National Vector borne disease control programme of the Union Ministry of Health and Family Welfare.
The threat of these small spindly insects remains constant. The emergence of a little-known virus – Zika – from an African forest is the latest alarm to the world. The same mosquito infects people with dengue and chikungunya viruses. What causes these deadly flying creatures to proliferate and kill?
According to Emory University’s environmental scientist’s Gonzalo Vazquez-Prokopec in an interview in the Science Daily in January this year, aedes aegypti are like “the roaches” of the mosquito world, perfectly adapted to living with humans, especially in urban environments. The scientist who studies vector-borne diseases says that while mosquitoes that carry malaria only feed during the evening, the aedes aegypti feeds almost exclusively on humans and bites primarily during the daytime.
Global warming is having a real impact with the encroachment of mosquito-borne diseases on new territory, including southern Europe. Mosquito-borne illnesses also include West Nile virus, elephantiasis, yellow fever and others but these infections are normally restricted to certain geographic areas. For instance dengue hemorrhagic fever is a viral, mosquito borne illness usually regarded only as a risk in the tropics.
However, cases of dengue fever have now been popping up in the US along the Texas-Mexican border where it has never been seen before. In 2015 it was also reported that, due to climate change, mosquitoes had started to spread historically rare diseases to Europe – malaria to Greece, West Nile virus to eastern Europe and chikungunya to Italy and France.
Mosquitoes are a perfect example of one of the many organisms that can host diseases, explains Dr Mahendra Jagtap, Joint Director of Health (Entomology), Maharashtra.
Human infection with a mosquito-borne virus occurs when a female mosquito bites someone while its immune system is still in the process of destroying the virus’s harmful coding. When a mosquito bites, she also injects saliva and anti-coagulants into the blood which may also contain disease-causing viruses or other parasites. This cycle can be interrupted by killing the mosquitoes, isolating infected people from all mosquitoes while they are infectious or vaccinating the exposed population.
Presently there is no vaccine yet and killing mosquitoes can be labor-intensive and expensive. Moreover despite all the buzz about genetically modified mosquitoes (where the male of the species can be sterilized making the killers kill themselves) few believe they represent a silver bullet against mosquito-borne diseases.
Authorities in India that is now home to dengue and chikungunya are gearing up to tackle the Zika viral infection transmitted by aedes aegypti. Clearly, these aggressive daytime biters are spreading fast and while the solution may lie in not getting bitten by covering up, scientists and researchers are now looking at newer ways to tackle this menace.
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