Taking the Bite Out of Mosquitoes

"With all the urgent crises facing our nation and the State of Florida -- the COVID-19 pandemic, racial injustice, climate change -- the administration has used tax dollars and government resources for a Jurassic Park experiment."            Jaydee Hanson, policy director, International Center for Technology Assessment and Center for Food Safety

"It’s gone extremely well. We have released over a billion of our mosquitoes over the years. There is no potential for risk to the environment or humans."                 Kevin Gorman, Oxitec scientist 

"The mosquitoes created in a lab have not gone through a natural selection process, in which only the fittest survive and mate. Once they are released in the natural environment, will they be as fit as the naturally occurring males and able to outcompete them for mates?"                                                                                "An ecosystem is so complicated and involves so many species, it would be almost impossible to test them all in advance in a lab."                                                    Max Moreno, expert in mosquito-borne diseases, Indiana University

A biologist in Brazil releases mosquitoes to combat a Zika outbreak   Getty Images

A project is underway in Florida, approved by authorities, to test if a genetically modified mosquito acts as an improved alternative to insecticides to control the spread of Aedes aegypti, the yellow fever mosquito. Known to bite to obtain blood to mature her eggs, the female mosquito spreads a number of exotic diseases like dengue fever, zika and chikungunya. 

A British-based lab, Oxitec, which created the mosquito named OX5034, succeeded in altering female mosquitoes to produce female offspring destined to die in their larval stage, thus preventing them from hatching and maturing to the point of biting for blood and successfully reproducing. Male mosquitoes, which are not disease carriers, have been programmed as well, to kill female mosquitoes.

The aim is to reduce the population of Aedes aegypti mosquitoes Getty

The company's promotions have emphasized that the genetically altered mosquitoes will not bite, despite which a public backlash against the experiment has arisen fiercely opposed to the experiment, with some residents stating they will not be treated as "guinea pigs" with the "Robo-Frankenstein" mosquito.

The concern among environmental activists is that a massive population of mosquitoes released for any purpose could result in a detrimental effect on wildlife, endangering bird species, insects and mammals that feed on mosquitoes. 

This is not the first occasion when Oxitec's altered mosquitoes have been put into action for the purpose of battling mosquito-borne disease.

The first such tests with the altered mosquitoes took place in May of 2018 when the mosquitoes were released within four communities in the city of Indalatuba, Brazil.There, success was realized when the outcome resulted in a reduction in the numbers of Aedes aegypti of 95% in a trial conducted in an urban area of Brazil.

"This is an exciting development because it represents the ground-breaking work of hundreds of passionate people over more than a decade in multiple countries, all of whom want to protect communities from dengue, Zika, yellow fever, and other vector-borne diseases."                                                                                      Oxitec CEO Grey Frandsen

Consorting With Mosquitoes

"Those with type-O blood are about twice as attractive to mosquitoes as those with type-
A, with type-B somewhere in the middle."
"Your skin bacteria can have an influence. We all have lots of different skin bacteria, but some are more attractive and [alternately] repulsive to mosquitoes. Heat is also important, so if you're the sort of person who tends to be running a little warmer than others, you probably attract mosquitoes a bit more."
"The classic advice is covering up. Humans are large, warm, and easy to spot. When it's warm, we're wearing shorts, T-shirts, and swimming costumes, so we have this perfect storm of behaviour."
"Darker colour and reds might make you easier to spot because mosquitoes have quite good eyes."
Professor Adam Hart, entomologist, University of Gloucestershire, Britain

"If you're outside at a time of day when insects are particularly active, such as sunrise or sunset, cover your skin wearing loose sleeves and trousers and wear shoes, not flipflops when outdoors."
"The bite causes inflammation, which causes itching. If you scratch it, it'll make the inflammation worse."
"And you may break the skin. The bite is a microscopic puncture, but if you scratch and scratch it then pretty soon you'll open the skin a lot more, and end up with secondary infections. The best advice is always the boring advice: not to scratch."
Dr. Nick Scriven, president, Society for Acute Medicine, UK

Like so much else, your genetics mandate how attractive mosquitoes will find your presence. Anyone who is a secretor ; whose saliva contains their blood type antigens; is more likely to be bitten by mosquitoes. One in five of a population are non-secretors, the lucky ones that don't attract the attention of mosquitoes. Famously it is female mosquitoes who bite to extract blood to enable them to lay their eggs to reproduce.

Sweat enables mosquitoes to detect warmth and chemicals and to track carbon dioxide that mammals exude. Metabolic rate affects susceptibility to mosquito bites; giving off higher levels of carbon dioxide is a guaranteed attractor to mosquitoes. Pregnant women with their higher-than-normal breath rates are consequently more prone to mosquito bites. Resting metabolic rate is raised as well, after drinking alcohol as well as post-exercise.

Avon's Skin So Soft gained a reputation as an effective mosquito repellent due to the citronella it contains. But Professor Hart's professional advice is to use repellents containing DEET, a liquid that people would prefer to avoid, citing its unpleasant odour. The imperative is to prevent mosquito bites "...they are really driven to feed on you. People think, 'Oh, we'll get away with it this time', but you probably won't", advises Dr. Hart.

• DEET
• Picaridin
• IR3535
• Oil of lemon eucalyptus (OLE)
• Para-menthane-diol (PMD)
• 2-undecanone

• Cover up: Wear long-sleeved shirts and long pants.
• Keep mosquitoes outside: Use air conditioning, or window and door screens. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.                                                                               Centers for Disease Control and Prevention, U.S.

The itchiness can be relieved with the use of antihistamines. Alternatively an ice cube placed directly on the bitten area of the skin serves to soothe the affected area. Also recommended by Dr. Hart is "that old faithful, Anthisan cream and just washing the bite with soap and water". Oil-based "bite ointment", comprised of lavender oil, coconut oil and beeswax has been produced by a number of pharmaceutical companies even though Dr. Hart "can't find any studies" testing lavender oil.

Additionally, Britain's National Health Service warns -- tea tree oil, herbal remedies, garlic and yeast extracts or anti-mosquito buzzers are all a waste of time and money and hope. None of them are known to be effective, despite the glowing promises of efficacy.

Eradicating Malaria

"With this achievement, the major barriers to saving lives are arguably no longer mostly technical, but social and diplomatic."
"The known harm of malaria greatly outweighs every possible ecological side-effect that has been posited to date, even if all of them occurred at once."
Kevin Esvelt, study, evolution of gene drives, Massachusetts Institute of Technology

"We are not saying this is one hundred percent resistance-proof. But it looks very promising."
"This is the first time we’ve shown that we can, in principle, manipulate the fate of an entire species."
Andrea Crisanti, biologist, Imperial College, London

Andrew Hammond

Among the world's worst disease scourges, caused by a parasite and transmitted by mosquitoes, in 2016 alone malaria infected 194 million people across Africa, causing 445,000 of that number to die an early death. Now comes news that biologists have succeeded in developing a manipulation of mosquito genetics forcing entire mosquito populations to self-destruct by making them incapable of reproducing. Laboratory research testing the technique has been so successful the researchers have determined that through their methodology malaria could be eliminated within 15 years, freeing large areas of Africa from their presence.

A research team, led by Andrea Crisanti disrupted the mosquito's sexual development by altering a gene rendering the females infertile while the males still capable of spreading the gene only produce a dwindling number of offspring, as a result. Through research, the team realized  their laboratory mosquito populations could be driven to extinction within the space of 11 generations. This signal finding was reported in Nature Biotechnology last month, spreading the news that wild populations of mosquitoes could be manipulated out of existence in four years, if computer models are to be believed.

In a study published last year, Andrea Crisanti, right, and his colleagues were able to spread an infertility mutation to 75 percent of a mosquito population. (Mike Kemp / Bill & Melinda Gates Foundation)

For the scenario to unfold it is dependent on the technique pioneered by these researchers to equip mosquitoes with a gene drive which is a genetic mechanism to force a gene into all of an organism's offspring. Gene drives can occur naturally without human intervention, but sexual reproduction passes genes to only half the progeny; installing a specific gene drive in an effort to alter genes interfering with reproductive capacity, all the progeny, not just a portion of them are affected.

This gene drive function has the capability of carrying forward a gene rapidly, producing a powerful and potentially dangerous effect. Dangerous in that successfully installing a gene drive in the wild would be an irreversible event; should it happen that such an advent triggers a like reaction in other creatures, it could result in another species being doomed to extinction. In the past, efforts to reduce mosquito fertility with the use of gene drives failed, since mutations arise in stretches of DNA scientists target and what results is the nullifying of the engineered alterations.

Engineering the gene --

(Graphic by Charles Floyd; Research by Molly Ginty)

However bypassing the possibility of mutations favoured by natural selection allowing the mosquito to escape from the trap was achieved by Dr. Crisanti and his colleagues when they discovered how to target a stretch of DNA that is unvarying from one mosquito to another. They found this DNA sequence in a gene named doublesex, specializing in determining sexual development, in one of the major carriers of the malaria parasite, Anopheles gambiae.

With the concern uppermost in mind of the potential risk in launching a gene drive into the wild which, once released cannot be recalled, cannot be contained within national borders or easily disabled, the researchers proceeded with caution. The U.S. National Academy of Sciences made it mandatory in 2015 for tests and public consultation to take place before the release of any gene drive.

And now, biologist Austin Burt of Imperial College, London, part of the research team, anticipates a field trial to be initiated in five years' time in Africa. "We wouldn't have to hit every village, maybe as few as one percent", he offered in the initial implementation where a few hundred drive-carrying mosquitoes would be released in each of the chosen villages.

The malaria parasite cannot maintain its populations once its numbers fall below a certain level, so total eradication is not an absolute requirement, before the species crashes.

On Alert to Evade the Tiger Mosquito in France

"Despite storms and rain, people in 30 departments across the south are being urged to look out for the pests which can transmit the Zika virus, as well as other diseases such as Yellow Fever, Dengue Fever, and Chikungunya."
"The species – originally of Asian origin – is well-established in Provence-Alpes-Côtes d’Azur and Midi-Pyrénées-Languedoc-Roussillon, as well as the Vendée, Haut-Rhin, Bas-Rhin and Val-de-Marne."
"So far this year there have been no reports of any tiger mosquitoes in France or any outbreaks of the diseases they can carry but the Health Ministry has issued a yellow alert and has set up a site where the public can record sightings at: www.signalement-moustique.fr"
"Anyone contracting any of the viruses transmitted by the tiger mosquito must report it to the health authorities via their doctor and people are also being asked not to leave stagnant water outside, such as water in saucers under flowerpots, as this provides breeding grounds for mosquitoes."
"The species has been spreading in France since 2004 and has now been seen across the south of the country as well as in Vendée, Haut-Rhin, Bas-Rhin and Val-de-Marne."
The Connexion, French News and Views, May 2, 2018

Tiger mosquitoes with black and white striped body and legs, can carry the Zika and dengue viruses. AFP Photo/EID Mediterranee

France reported more than half of the 2,133 cases of Zika infection in the European Union. Between June 2015 and March 2017, 1,141 Zika infection cases were reported in France. Notoriously, in pregnant women, the Zika virus has the potential of spreading to the fetus to cause severe birth defects like microcephaly, impeding brain development. Zika can be transmitted by mosquitoes or spread sexually.

Dengue fever and Zika have similar symptoms that can most often be mild so that healthy adults though infected may present with no symptoms whatever. For babies there is an altogether different story. If infected they are born with abnormally small heads while the neurological disorder may lead to an early death. Among all European countries France was affected most seriously by the Zika epidemic that hit South and North America in 2015 and 2016.

The aggressive tiger mosquitoes known to carry viruses such as Zika, Dengue and Chikungunya have now spread over half of France, leading authorities to warn the population, particularly those planning to travel on vacation to areas that the invasive insects are known to habituate themselves to; to make use of repellents. Originating in Asia, the insect is recognized by its black-and-white striped body and legs.

The South of France constantly reveals delightful surprises. Sète's canals have earned it the nickname of the "Little Venice" of France.

The south of France, famous the world over for its sunny atmosphere and sandy beaches now plays host as well, to these striped mosquitoes. As does the centre of the country, the southern Paris suburbs and pockets of the north of the country. The presence of the mosquitoes is known to have doubled in the past two years in the identified areas of infection. Of 86 departments (electoral areas or cantons) in France, 42 are now affected.

People are being urged by France's public health authority to be watchful for the presence of the mosquitoes between May and November, to "drain away stagnant water, where mosquitoes can reproduce, around homes". On the French island of Reunion in the Indian Ocean, tiger mosquitoes are responsible for having propagated an epidemic of Dengue fever, leading to fears among health authorities that returning vacationers could conceivably carry the virus to mainland France.

There may be no better way to spend a day than soaking in the Mediterranean sun in the South of France, and have frosty drinks and lunch delivered to your chaise lounge - with an average of 320 days of sunshine per year.

In southern France in 2014 and 2015, 18 cases of locally transmitted Dengue Fever were recorded, and 17 of Chikungunya on the Riviera last year. Making those world-famous vacation spots for the trendy and the financially care-free somewhat less inviting than how they have traditionally been regarded. Most who contract the virus, however, can expect to be inconvenienced by symptoms of Dengue and Chikingunya that include severe joint pain, fever, headaches, weeping eyes and a rash.

Tiger mosquitoes have spread across France