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Repelling mosquitoes is big business, attracting both science and snake oil

By George W. Russell

Local governments on both sides of the Pacific Ocean are formulating a variety of mosquito prevention strategies as the Zika virus continues to spread. Meanwhile, unscrupulous entrepreneurs are trying to extract cash from concerned consumers by selling them bogus mosquito repellents.

In Honolulu, officials are spraying adult mosquitoes with pesticide appealing to residents to get rid of standing water to prevent eggs being laid and larvae hatching. Some municipalities – from Tainan in southern Taiwan to Whitsunday in northern Australia and Da Nang in central Vietnam – have taken a more authoritarian approach, mandating home inspections as well as spraying.

With Zika fears mounting as the disease spreads – it is already been found in 87 countries and 4 million cases are expected by the end of this year in the Americas alone – it is no surprise that businesses have rediscovered the anti-mosquito market, introducing a variety of products, including some of dubious efficacy.

The standard control method is aerosol-delivered pesticide, usually composed of synthetic pyrethroids such as permethrin and piperonyl butoxide. However, these compounds also kill flies and other insects, including bees, as well as fish and other forms of aquatic life. The World Health Organization’s Vector Control Advisory Group (VCAG) has been seeking novel control methods that are less harmful to other species as well as safe for the environment.

One method VCAG has backed is a genetically modified male mosquito, which mates with wild females to produce non-functioning offspring, developed by Oxitec, a biotechnology company based in Oxford. Hadyn Parry, Oxitec’s Chief Executive Officer, says the OX513A transgenic male mosquito is among “effective, scalable solutions to combat the… primary vector for a number of harmful arboviruses including Zika, dengue and chikungunya.”

Other recently developed products are more down-to-earth. Houston-based MosquitoMax this month introduced a battery-powered larvicide-dispensing system aimed at local governments as well as households and commercial operations such as golf clubs.

However, some newly launched devices claim to use ultrasound or electromagnetic waves to repel the insects. Other vendors tout bracelets, patches and vitamin supplements to discourage their bites. One U.S. company, Insect Shield, offers a dog bed doused with repellent, claiming it “repels mosquitoes that may carry Zika virus.” (Neither Zika nor other arboviruses are known to infect dogs).

In 2015, the U.S. Federal Trade Commission took action against Tennessee-based Viatek Consumer Products Group for claiming a bracelet doused in mint oil was an effective repellent. However, similar products are still for sale on Amazon. One brand received 21 five-star assessments, all mentioning Zika, within a week in March, prompting suggestions from other users that the reviews were faked.

Joseph Conlon, technical adviser at the American Mosquito Control Association (AMCA), told Dow Jones Newswires that “natural” products such as garlic, marigolds, cloves and lemons were ineffective. The most effective repellents, according to the AMCA, are those containing N,N-diethyl-meta-toluamide (DEET), hydroxyethyl isobutyl piperidine carboxylate, also known as picaridin, and ethyl butylacetylaminopropionate, or IR3535.

The U.S. Centers for Disease Control and Prevention’s recommendations to prevent mosquito-spread diseases include insect repellents, mosquito nets and wearing long pants and long-sleeved tops when outdoors. Hong Kong authorities concur, adding that, locally, removing standing water is the most vital step in prevention. Potential breeding grounds can be as small as a bottle cap, while common sites include plant pots, vases, empty cans, old tyres and even temporary puddles.

Hong Kong is on particular alert because of increasing evidence that the most common local mosquito species, Aedes albopictus, can transmit the Zika virus as well as dengue fever. As a result, authorities are gearing up for the onset of warmer weather. “Mosquito eggs can hatch in a short period of time when the weather turns warm and humid, leading to a large amount of adult mosquitoes,” says a spokesman for the Food and Environmental Hygiene Department.

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