February 12, 2016

Spread of Dengue could be Stemmed

Spread of Dengue could be Stemmed

A female Aedes aegypti mosquito feeds on human blood. As it does so, the small insect often transmits deadly pathogens into people's bloodstreams. Photo Credit: Wikimedia Commons

The world’s greatest killer is at it again. It’s relentless – spreading pain, suffering and heartache everywhere in its wake. Its bite is a mere pinprick, yet it has the potential to transmit deadly pathogens into bloodstreams within mere seconds. We’re speaking of mosquitoes, of course.

Mosquito bites result in the death of up to 1 million people worldwide each year, most of them from malaria transmitted by these pesky insects. Throughout history, mosquitoes may well have contributed to the death of almost 50% of the people who have ever lived. And in Malaysia, as elsewhere across Southeast Asia, it isn’t just malaria that mosquitoes spread; it’s also dengue fever, another potentially deadly disease, of which there have been 18,500 cases this year alone, between January 1 and February 10. Selangor recorded the highest number at 9,034, followed by Johor, at 2,827 cases, and Wilayah Persekutuan Kuala Lumpur, at 1,145.

The virus that causes the debilitating tropical disease (which is an especial risk to children, the elderly and people with compromised immune systems) is transmitted by the females of two types of mosquitoes: Aedes aegypti and Aedes albopictus. Both of them are active during daytime and often proliferate inside and near houses where stagnant water is left in accessible containers (such as in water tanks, reflecting pools and flower pots), allowing them to lay their eggs.

To make matters worse, another crippling, mosquito-borne disease has been spreading slowly but relentlessly around the globe. The Zika virus causes microcephaly (abnormally small brains) in infants and paralysis in adults. Although there have been no reported cases of the virus yet in Malaysia, Health Minister Dr S. Subramaniam has warned that the country, long plagued by dengue fever, was a potential breeding ground for Zika as well. That is because the same mosquitoes that spread dengue fever can also spread the Zika virus. Complicating matters is that there are no known drugs to treat the disease and many people who are already infected with the virus, which is especially dangerous to pregnant women, do not show any symptoms. “These are challenges we need to manage,” Subramaniam said.

Now even many environmentalists, who otherwise work tirelessly to save endangered species, believe that the time has come not just to “manage” situations but to do away with disease-carrying mosquitoes once and for all. A pipe dream, you say? It may certainly look that way, considering the ease with which mosquitoes can breed and proliferate, defeating almost any effort that aims to do more than merely contain them. Yet it is no mere pipe dream any longer.

Scientists worldwide are working on solutions to eliminate Aedes aegypti mosquitoes for good.  In Colombia, specialists are trying to infect mosquitoes with Wolbachia bacteria, which block the insects’ ability to pass on diseases to their human hosts. In Mexico, scientists are zapping male mosquitoes with radiation to make them sterile before they set the male insects loose among wild female populations in the hope that females will no longer be able to produce any offspring. In the United Kingdom, geneticists are seeking to achieve a similar result by manipulating the genes of males so that their offspring will all be sterile.

“Ultimately I wouldn’t be too sentimental” about killing them off, Professor Steve Lindsay, said an entomologist at Britain’s University of Durham who is working on the gene manipulation of mosquitoes. “I have no problem with taking out the mosquito.” Nor will anyone else. we’d wager.

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