MOSQUITOES
aedes Mosquitos are flies (their name means "little fly" in Spanish). They first appeared bout 170 million years ago during the age of the dinosaurs, and today they are found in virtually every part of the world. The species that causes yellow fever and malaria are believed to have diverged about 150 million years ago.
There are 3,500 species and subspecies of mosquito, three fourths of which live in the tropics. Once they have left the larval stage, mosquitoes typically live 7 to 10 days. Some females live as long as 30 days. If the weather is too hot, mosquitoes quickly dehydrate and die. [Sources: Lewis Nielsen, National Geographic, September 1979; David Schwartz, Smithsonian; David Zimmermann, Smithsonian]
Mosquitoes fly at a speeds around 3mph. The buzzing noise produced by mosquitoes is generated by wings flapping at a rate of 200 to 500 beats a second. Mosquitoes can cover long distances. Some have been captured 100 miles out at sea. They are most vigorous in temperatures above 80̊F. They get sluggish at 60̊F and disappear when the temperatures drop below 50̊F. The can hibernate through the winter and spring back to life when the temperatures warm.
On a day to day basis both sexes feed on flower nectar and fruit juices like other insects. These are the only things that males feed on. Females need protein-rich blood to produce viable eggs. They extract blood not just from humans but from a variety of creatures and are attracted by the body heat, carbon dioxide and the lactic acid and folic acid in the sweat of prey, which they can detect more than a 100 feet away.
See Separate Articles:VECTOR-BORNE DISEASES CAUSED BY MOSQUITOES, TICKS AND FLIES factsanddetails.com; YELLOW FEVER factsanddetails.com; DENGUE FEVER factsanddetails.com; MALARIA: ITS HISTORY, PARASITE AND ITS LIFE-CYCLE factsanddetails.com; COMBATING MALARIA: NETS, DIRTY SOCKS, DNA AND VACCINE EFFORTS factsanddetails.com; ARTEMISININ AND MALARIA MEDICINES, TREATMENTS AND DRUGS factsanddetails.com; MALARIA ERADICATION AND DDT factsanddetails.com
Websites and Resources Centers for Disease Control and Prevention (CDC) cdc.gov/DiseasesConditions ; World Health Organization (WHO) fact sheets who.int/news-room/fact-sheets ; National Institute of Health (NIH) Library Medline Plus medlineplus/healthtopics ; Merck Manuals (detailed info many diseases) merckmanuals.com/professional/index
Book: “ Mosquito: A Natural History of Our Most Persistent and Deadly Floe” by Andrew Spielman and Michael D'Antonio (Hyperion, 2001)
Mosquito Mating and Young Mosquitoes
Females may go through several cycles of mating, feeding, and egg laying. A stomach full of blood signals the female to start producing eggs. Females mate just once, storing the sperm in special pouch to fertilize several batches of eggs. Each batch requires a new meal of blood. The male dies soon after mating. After ejaculating sperm some mosquitoes produces a kind of plug which seals the female's orifice and prevents other males from impregnating the female.
Some species of mosquito lay their eggs directly in water. Others lay them in a dry area expected to flood. In places with human populations, mosquitoes often lat their eggs in bird baths, pet dishes, puddles, small pots, potted plants, and old tires. Mosquitoes take advantage of every bit of standing water to lay their eggs. That is why there are so many mosquitoes in tundra regions, which floods after the spring thaw. Scientists in the Canadian Arctic have recorded attack rates of 9000 bites a minute, enough to cause a person to lose half his blood supply in two hours and cause death.
Generally, within a few days after the eggs are laid they hatch, releasing larvae that swim around, breath through snorkels and survive off organic material. After molting for the fourth time, which occurred about a week after hatching, the larvae becomes pupa which do not eat and float around the water. A few days later the pupa skins break open and a mosquito emerges and flies away and is ready to mate and start the cycle over again.
How Mosquitoes Extract Blood
Only female mosquitoes bite. They are capable of carrying three times their body weight in blood. They need the protein and nutrient-rich hemoglobin in the blood to nourish their eggs. One good feeding provides enough nutrients for 75 to 500 eggs. Males have no interest in blood.
To find food, mosquitoes first sense carbon dioxide from the breath of a victim. That prompts them to scan for certain colors and visual patterns that could indicate food. To extract blood a female places its proboscis (a long tube that extends from the mouth) in the skin and penetrates the skin with a mandibles that flip out of her mouthpart like switchblade. When the skin is pierced a pair of tubes called fascicles enters the body to search for blood. A mosquito’s proboscis looks like a solid spike but is actually a composite of cutting blades and feeding tubes, powered by two tiny pumps. After taking position on a female drills through layers of epidermis and fat until she reaches blood-filled micro-capillaries and the starts to drink.
aegypti Once the a capillary is pierced by the fascicles, two powerful pumps inside the female’s head draw out the blood. Mosquito's saliva contains hundreds of chemicals, including anticoagulants that prevent the blood form clotting and compounds that dilate the capillaries to increase flow. A mosquito often draws its own body weight in blood in one feeding.
Mosquitoes have an efficient anticoagulant in their saliva. When mosquitoes bite they deposit a protein that keeps the blood from coagulating as they drink it. The body responds by producing histamines to fight off the invaders. It the histamines that cause the skin to swell, turn red and itch.
Speed is critical. The mosquito usually lands, finds the blood and sucks it less than two seconds. Those that linger to long are often swatted and killed. Weighted down by the blood it usually flies some place to rest. There are still things about the process that scientists don’t understand. For example friction should make sucking blood through a feeding tube with an infinitesimally small diameter impossible.
Japanese medical researchers have been able to reduce the pain of an injection by using hypodermic needles edged with tiny serrations, like those on a mosquito’s proboscis, minimizing nerve stimulation.
Swarms of Mosquitoes Kill Hundreds of Horses and Cows by Draining Blood
In September 2020, parts of Louisiana in the U.S. hit hard by Hurricane Laura also had to deal with huge swarms of mosquitoes that killed hundreds of farm animals by biting them in such huge numbers the animals died from a loss of blood, anemia, bleeding under the skin and exhaustion caused by constantly moving to avoid the insects. [Source: Andrew Naughtie, The Independent, September 12, 2020]
Dr Craig Fontenot, a vet in the city of Ville Platte, said the “vicious little suckers” were pushed out of marshes by the huge storm and killed 300 to 400 cattle, as well as some horses. Goats have so far been spared as they are kept in stalls that can be sprayed with insecticide, but one deer rancher has lost at least 30 of his animals.
Associated Press and The Independent reported:“Large-scale insecticide spraying efforts are underway to fight the hordes of bloodsucking insects. In Acadia County, local Lousiana AgCenter agent Jeremy Hebert reported that "the spraying has dropped the populations tremendously. It's made a night-and-day difference", though other counties are still struggling to turn the tide.
“Hurricanes often present a risk of surging mosquito populations, as eggs laid by floodwater mosquitoes in previous floods start to hatch. While adult mosquitoes generally do not survive a hurricane’s high winds, the egg-hatching phase that kicks in after a storm can drive a huge increase in the population.
Mosquitoes Prefer Blondes and the Color Red
Mosquitoes seem to prefer some humans over others — children over adults, blondes over brunettes and blacks more than whites — and aggressively go after some people and leave others alone. It is still not known why this is so. Scientist thinks that this because some people give off chemicals that attract them and others gives off chemical that repel them. Scientists in Britain took the body odor of people that turned mosquitoes off and applied it to people who attracted mosquitoes and found that the body odor repelled the mosquitoes.
In a study published in the journal Nature Communications in February 2022, researchers from the University of Washington tracked the behavior of female Aedes aegypti mosquitoes and found they had preferences for different types of visual and scent cues. Korin Miller wrote in Prevention: The researchers put the mosquitoes into small test chambers and exposed them to different things, like a colored dot or person’s hand. [Source: Korin Miller, Prevention, February 10, 2022]
When there was no odor like carbon dioxide, which mosquitos usually follow to find food, in the test chambers, the mosquitos pretty much ignored the colored dot, not matter what hue it was. But once researchers sprayed carbon dioxide in the chamber, they flew toward dots that were red, orange, black, or cyan. Dots that were green, blue, or purple were ignored.
anopheles adult
“Why are mosquitos attracted to the color red? This particular study didn’t dive into that, but there are some theories. One is that red is simply the shade of color mosquitoes see when they look at your skin. “When light interacts with human skin, regardless of skin pigmentation, it reflects a reddish color,” explains Nancy Troyano, Ph.D., a board-certified entomologist and Director of Operations Education and Training with Ehrlich Pest Control. “Therefore the color red may be one of several cues that mosquitoes use to help them to locate their host.”
“It’s easy to assume that mosquitoes associate the color red with blood, but board-certified entomologist Timothy Best, technical manager at Terminix, says that's “unlikely.” “While mosquitoes can see using their compound eyes, their acuity is poor, and they do not see clear images,” he says. Mosquitoes actually rely on three separate sensing mechanisms to find blood, he says. Those include detecting respiratory gases like carbon dioxide, visually identifying a host, and using a heat sensing receptor in its antenna to follow up on this visual cue to exposed and unprotected parts of your body.
“What about orange, black, and cyan? These colors tend to be darker, which mosquitos like, Best says.“Light colors are perceived as a threat to mosquitoes, which is why many species avoid biting in direct sunlight,” he says. “Mosquitoes are very susceptible to dying by dehydration, therefore light colors may instinctually represent danger and prompt avoidance. In contrast, darker colors may replicate shadows, which are more likely to absorb and retain heat, allowing mosquitoes to use their sophisticated antenna to locate a host.”
“Should you avoid wearing certain colors during mosquito season? Not necessarily. “Remember that mosquito attraction to people is a combination of several factors, from chemical cues including odors from sweat and carbon dioxide, as well as heat, and visual cues such as color,” Troyano says. Basically, there’s more to a mosquito’s attraction to you than just what you’re wearing.
Mosquitoes and Disease
Mosquitoes are thought to transmit more diseases than other creature. There are more than 500 known mosquito-borne viruses, but not all of them have harmful affects on humans.
Of the roughly 3,500 mosquito species, around 100 spread human disease. The most worrisome and deadly are the dozen or so species in three genera — Anopheles (translation: “useless,” the malaria mosquito), Aedes (translation: “unpleasant,” the principal vector for yellow fever, dengue and Zika) and Culex (translation: “gnat,” responsible for spreading West Nile, St. Louis encephalitis and other viruses).
Jerry Adler wrote in Smithsonian magazine: “Mosquitoes flit about the villages and cities of central Africa, land silently on sleeping children and bite. The fight against malaria has made much progress in the last decade, but at a huge cost that may not be sustainable indefinitely. In the Western Hemisphere, the threat of Zika has led to extraordinary measures, including warnings in whole regions of South and Central America for women to consider postponing childbearing. This summer will tell us if the disease will strike in the parts of the U.S. where two Aedes species live — Florida and a strip of the Gulf Coast that is likely to expand as the winters warm in a changing climate. (The second of those two American Aedes species, A. albopictus, is a confirmed carrier of the virus and can be found as far north as New England.) Public-health officials are already bracing for the possibility of a spate of babies with the devastating diagnosis of microcephaly and associated brain damage. It was human transportation technology that spread these diseases across the globe. Now technology is offering a way to contain them, or even defeat them altogether, at the risk of unleashing powerful forces whose effects we can only dimly predict. [Source: Jerry Adler, Smithsonian magazine, June 2016]
Avoiding Insects and Preventing Mosquito Bites
gambiae According to the Centers for Disease Control and Prevention (CDC), the primary ways to prevent mosquito bites are: 1) Using insect repellent with ingredients registered with the Environmental Protection Agency, like DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, and 2-undecanone; 2) Wear long-sleeved shirts and pants; 3) Treat your clothes with 0.5 percent permethrin; 4) Get rid of standing water around your home or empty items that hold water like bird baths, toys, and planters weekly; 5) Use screens on your windows and doors
For protection from insects use an insect repellent with at 30 percent DEET (some people recommend 95 to 100 percent), treat clothing with "Coulston's Duranon Tick, spray, and sleep under an insecticide-impregnated insect netting.
Disease-carrying mosquitoes, like most mosquitoes, generally bite at night between dusk and dawn, and are particularly fierce around sunset. An exception to this rule are mosquito that carries dengue fever. They generally bite in the day. Mosquitoes generally go for the lower extremities of the body. People with a high skin temperature and high moisture-transpiration rates sometimes attract more mosquitoes.
The best way to avoid disease-carrying mosquitoes and insects is avoid the places where the diseases are known to exist. The Center of Disease Control can provide information on countries and regions where diseases are found. Rural areas are generally more risky than urban areas. Local people can often provide information on specific risky places in their area.
The best way to avoid mosquitoes is to: 1) stay inside when they are most active (in the late afternoon, early evening, and early morning); 2) sleep under a mosquito net (tucked under the mattress and treated with an insecticide); and 3) stay in hotels that are well-screened or air-conditioned, if screens are insufficient ask for mosquito netting. Fans and mosquito coils are also effective in keeping mosquitoes away. Sandals should be avoid and pants should be tucked into socks in places with lots of ticks. White or light clothing makes ticks easier to spot. Many Africans who live malaria-endemic areas use nets but still get mosquito-born disease. Many people in hot countries don't like nets because the keep out the breeze.
DEET and Permethrin
Use a DEET insect repellent on your skin. DEET is a strong chemical that interferes with the tiny sensory hairs and pits in the antenna and body it uses to detect carbon dioxide. DEET is toxic if ingested; stings eyes severely; and can blister the skin in high concentrations. Repellents with 30 to 35 percent DEET are good at repelling mosquitos. They the usually only last for around five hours. Higher concentrations, such a 95 percent to 100 percent, don’t add any more protection but they last longer. Aerosol insecticides and mosquito coils help to clear rooms but they sometimes contain DDT. Non-DEET repellants generally work 1½ hours or less.
DEET is the most widely used commercial insect repellent. It offers powerful protection from insect-borne illnesses such as malaria and dengue fever but it is toxic in high concentrations, expensive, and short-lived. Some people are turned off by the odor of DEET and the chemical is not suited for all ages. Alternatives include the chemical Picaridin and the plant-based oil of lemon eucalyptus. The Centers for Disease Control and Prevention recommend products containing DEET, picaridin, IR3535 and the oil of lemon eucalyptus. They say put some on you clothes for greater protection. If you wear sun screen, apply the insect repellant on top of it. [Source: CDC, Caroline Spivack, Discover, January-February 2012]
Use a spray or repellent with Permethrin or Permanone (such as Coulston's Duranon Tick Repellent) on your clothes, shoes, tents, camping gear and bed netting. Permethrin often maintains its potency through ten or more washing. It bonds tightly with cotton fabric and It is effective enough to knock out a mosquito by the time sticks its probe through the cloth and it aims it towards the victims skin.
Short History of Mosquito Repellents
Over the centuries a variety of concoctions with things like vanilla, eucalyptus sassafras, cloves, citronella, and pennyroyal have been touted as effective insect repellents. “ Geoponika” , a collection of classical Greek agricultural writings published in the A.D. 6th, recommended using salt alum to get rid of flies and bats and was tied to tall trees kept locusts away.
Researchers sometimes check the mosquito concentration in a given area by rolling up their pant legs and counting how many times they get bitten in a certain length of time. Scientists measuring the effectiveness of repellants count number of mosquitoes that bite per minute when an forearm is exposed to mosquitoes inside a tank. One scientist told Smithsonian magazine, "It isn't difficult to find substances that repel insects. What's difficult is finding a truly useful repellant that lasts a long time against a variety of pests under a variety of conditions and doesn’t harm people.
Shortly after World War II, researcher who had tested over 20,000 compounds in an effort to find sometime to protect U.S. servicemen in the Pacific from insect-borne diseases, discovered a chemical that deterred all known insect pests twice as long as any previous compounds. The new chemical, “ N.N. dieth-meta” -toluamide (later called "DEET") was added in 1957 to a new insect repellant called Off! and three years later to Cutter’s. The drug was tested by men who stuck their arms into tanks filled mosquitoes.
DEET is the most widely used insect repellant in the world. For a long time scientists weren’t sure how DEET worked. In 2008 , a team at Rockefeller University in New York lead by Leslie Vosshall announced in the journal Science they discovered that it affects the mosquito’s nose by blocking a highly-specific molecular pathway that tells the insect’s brain what it is smelling. In particular, it interferes with he ability of the mosquito to smell 1-octen-3-ol — a telltale ingredient of human breath — and lactic acid, one of the smellier sweat component. Researchers Walter Leal and Zainukabeuddin Syed didn’t agrees with this conclusion. They argue that mosquitoes simply dislike the stuff. They came to this conclusion by using several different delivery systems that responded to different senses — of which smell was just one — and found that mosquitoes were turned off to them in every case.
A toxicant known as permethrin and by the trade name Permanone Tick Repellant was developed in the early 1980s.
In May 2011, Vanderbilt University biologist Laurence Zwiebel announced that he had produced a compound called VUAA1, that he touted as a better alternative to DEET that not only is 100,000 times as strong as DEET but also potentially cheaper and less harmful to humans. Discover magazine reported: “The key to the improved repellent is its mode of action. DEET seems to work by inhibiting cells on an insect’s antennae, dulling its ability to locate prey. VUAA1, which Zwiebel discovered after screening 117,000 chemicals, stimulates a single receptor cell, called Orco. When triggered, Orco causes every type of odor cell to fire, overstimulating the bug’s olfaction system and disrupting its ability to sniff out humans—or anything else. “I’m hoping to repel bugs from crops, grain storage, and people,” Zwiebel says. “To have an impact across those aspects of human life would be extraordinary.”
Efforts to Eradicate Mosquitos
Jerry Adler wrote in Smithsonian magazine: ““Humans have been at war with members of the family Culicidae for over a century, since the pioneering epidemiologist Sir Ronald Ross proved the role of Anopheles in malaria and U.S. Army Maj. Walter Reed made a similar discovery about Aedes aegypti and yellow fever. The war has been waged with shovels and insecticides, with mosquito repellent, mosquito traps and mosquito-larvae-eating fish, with bed nets and window screens and rolled-up newspapers. But all of these approaches are self-limiting. Puddles fill up again with rain; insects evolve resistance to pesticides; predators can eat only so much. [Source: Jerry Adler, Smithsonian magazine, June 2016]
Jerry Adler wrote in Smithsonian magazine: “Starting in the 1950s, the American entomologists Edward F. Knipling and Raymond C. Bushland eliminated the screwworm, an agricultural pest, from the United States and much of Central America. Their approach, called “sterile insect technique,” involved breeding and hatching millions of flies, sterilizing the males with low-level gamma rays, then releasing them in numbers sufficient to swamp the wild population. Females that mated with the sterile males produced infertile offspring. It took decades, but it worked — the two men were awarded the World Food Prize in 1992 — and the same technique now is used to contain outbreaks of the Mediterranean fruit fly.
“But when the sterile insect technique was tried against mosquitoes, the results were mixed. It requires that the released males compete successfully with their wild counterparts in mating, and there is evidence that in mosquitoes, the same radiation that makes them sterile may also impair their mating behavior. Whatever female mosquitoes are looking for in a mate, these males seem to have less of it.
Mosquito Eradication, See Malaria
DNA Technology That Could Potentially Kill All Mosquitoes
In 1994, molecular genetics had suggested a new approach to eradicating mosquitoes. Jerry Adler wrote in Smithsonian magazine: “Scientists had discovered how to insert beneficial mutations — such as the gene for Bt, a natural insecticide — into agricultural crops such as corn. Why not, then, create a lethal mutation and insert it into the DNA of a mosquito? One problem was that mosquitoes weren’t bred in a factory, as commodity corn increasingly is. In the wild, mosquitoes mate randomly and propagate by Mendelian inheritance, which dictates that a mutation spreads slowly, if at all. Unless the man-made mutation conveyed some strong evolutionary advantage — and the whole point was to do the opposite — it would most likely disappear. [Source: Jerry Adler, Smithsonian magazine, June 2016]
“In 2003, Austin Burt at Imperial College, suggested a solution: coupling the desired mutation with a “gene drive” that would overwrite the ordinary processes of inheritance and evolution. Recall that genes are spelled out by DNA sequences woven into chromosomes, which come in pairs (23 pairs in a human, 3 in a mosquito). A “gene drive” involves copying a mutated gene from one chromosome onto the other member of the pair. The key is that when the pairs split to form the eggs and sperm, it won’t matter which chromosome gets passed along — the engineered gene will be there either way. Thus a single mutation would, in theory, be “driven” into practically every mosquito in a breeding population.For the next dozen years, Crisanti, working with a senior research fellow named Tony Nolan and others, obsessively pursued variations of this approach, designing one gene mutation that would render females sterile and another that would lead to a huge preponderance of males. The challenge was creating the particular gene drives that duplicated those mutations — a tedious, years-long process of constructing custom DNA-snipping enzymes.
“Then, in 2012, the UC Berkeley researcher Jennifer Doudna and her colleagues developed a revolutionary new technique for editing DNA. Researchers had known for years that certain genes in bacteria had short, repeating chunks of DNA. (CRISPR stands for “clustered regularly interspaced short palindromic repeats.”) When a virus invaded, the bacteria copied part of the virus’ genetic code, slotting it into the spaces between the repeating CRISPR chunks. The next time the bacteria saw that piece of code, an enzyme called Cas9 would guide its RNA to exactly that sequence in the gene of the invading virus. It would cut out the DNA with incredible precision and fuse the strand back together. Doudna and her colleagues harnessed this process in the lab, using it to quickly and easily edit any part of a gene they targeted. The following year, separate teams led by MIT bioengineer Feng Zhang and Harvard’s George Church showed it would work in living cells.
Andrea Crisanti at Imperial College, London is using CRISPR technology to engineer ways to eradicate malaria-carrying mosquitoes. “It was the universality as well as the accuracy that set CRISPR-Cas9 apart from other gene-editing techniques. Unlike the custom enzymes Crisanti and his team had been painstakingly building, Cas9 seemed to work in any type of cell. Researchers saw implications for treating genetic disorders, for improving agriculture — and for more sinister applications, such as creating biowarfare agents. CRISPR also brought Crisanti’s dream a giant step closer to reality. Now, he and his team could program Cas9’s guide RNA to pinpoint any part of a gene and transfer over the material they wanted to copy.
If Crisanti’s approach works, you could, in theory, wipe out an entire species of mosquito. You could wipe out every species of mosquito, although you’d need to do them one at a time, and there are around 3,500 of them.
Mosquito Genomes
In 2002, scientists published the genome — a map of all the DNA — of Anopheles gambiae, the mosquito that carries malaria. It turns out the genetic make up of this mosquito is less complex than Aedes aegypti — the mosquito that carries yellow fever and dengue fever. The genome for Aedes aegypti was published in 2007.
In 2010, scientists announced in articles published in the journal Science said that had determined the DNA sequence of the most common mosquito species in the world, whose Latin name is Culex pipiens quinquefasciatus but which is more commonly known as the southern house mosquito. It was the third in the triad of major disease-causing mosquitoes to have its genome sequenced. The two studies published in
The southern house mosquito is the main vector for West Nile virus, which usually causes mild, flu-like symptoms but in severe cases can cause a form of encephalitis, an inflammation of the brain, or meningitis. It can also carry St Louis encephalitis virus and a worm that causes the disorder of the lymphatic system, elephantiasis. "Culex pipiens quinquefasciatus is the most widely distributed mosquito in the world, and in terms of disease transmission to humans it's one of the three most important mosquito species," said University of Texas Medical Branch at Galveston (UTMB) professor Stephen Higgs, one of the reports' authors."This work gives us a terrific platform to improve our understanding of the dynamics of infection, which has to be done if we're going to find ways to interrupt disease transmission." [Source: AFP, October 1, 2010]
AFP reported: Researchers from nearly 40 institutions in the United States and Europe were involved in sequencing the genome of the southern house mosquito, Researchers said they have identified all of Culex quinquefasciatus' 18,883 genes. Each gene in the mosquito can produce one of the proteins that make up the mosquito and determine its behaviour, including the way its immune system responds to infection by viruses, bacteria and parasites."This is really exciting for us, because we can finally perform experiments that we've wanted to do for years," said UTMB assistant professor Dana Vanlandingham, a co-author of the Science reports. "Our basic question is why do certain mosquito species transmit a particular virus and other mosquito species do not? Why don't they all carry all the viruses? We don't know, but now we have three different systems for comparative studies to investigate interactions between viruses and mosquitoes."
Disease-Carrying Mosquitos Moving North as a Result of Climate Change
The climate in northwestern Europe and the Balkans is becoming warming enough to accommodate the Asian tiger mosquito, a disease-spreading invasive species, scientists from at the University of Liverpool said. According to the scientists progressively milder winters and warmer summers have created conditions that favour the mosquito, which gained a foothold in Albania in 1979 and is now present in more than 15 countries on Europe's southern rim. "Over the last two decades, climate conditions have become more suitable over central northwestern Europe — Benelux, western Germany — and the Balkans," they said. At the same time, drier conditions in southern Spain have made that region less welcoming for the insect, they said. [Source: AFP, April 24, 2012]
AFP reported: The Asian tiger mosquito (Aedes albopictus), a native of tropical and subtropical areas of Southeast Asia, can transmit viruses that cause West Nile fever, yellow fever, dengue, St. Louis and Japanese encephalitis and other diseases. In 2005-6, it caused an epidemic of chikungunya, a disease that attacks the joints, on the French Indian Ocean island of Reunion. A year later, it unleashed an outbreak of chikungyuna in the Italian province of Ravenna. In 2010, it was fingered as a transmitter of dengue virus in France and Croatia. As of last December, the mosquito was present in more than 15 countries, from southern Spain to parts of Greece and Turkey, according to the European Centre for Disease Prevention and Control (ECDC).
Reporting in Britain's Journal of the Royal Society Interface, the Liverpool team looked at European weather records for 1950-2009 and ran a widely-used computer model to simulate weather trends for 2030-2050. "Similar trends are likely in the future with an increased risk simulated over northern Europe and slightly decreased risk over southern Europe," says the study. "These distribution shifts are related to wetter and warmer conditions favouring the overwintering of A. albopictus in the north, and drier and warmer summers that might limit its southward expansion."
In the mid-1960s, the Asian tiger mosquito was limited to some parts of Asia, India and a handful of Pacific islands.It has since spread to North and South America, the Caribbean, Africa and the Middle East, as well as Europe, mainly by hitchhiking a ride in exported materials. The paper points out that weather alone does not mean that the species will automatically spread there. It also notes that the study did not consider vegetation or soil types which also determine whether the mosquito would be able to breed there. In addition, cold snaps or hot, dry spell also help limit mosquito survival, and these too were not included in the investigation.
Image Source: Centers for Disease Control and Prevention cdc.gov/DiseasesConditions
Text Sources: Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human Services; World Health Organization (WHO) fact sheets; National Geographic, New York Times, Washington Post, Los Angeles Times, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides and various websites books and other publications.
Last updated May 2022