THE world’s most effective killer has arrived in the UK and could soon become widespread.

The mosquito, which is responsible for around half the deaths in human history, has been found in England and it is predicted that this is just the start of a mass invasion.

A species of Culex mosquito, the main carrier of the West Nile virus, has been discovered in the south of England and it is feared that climate change will bring the even more deadly Asian tiger mosquito, a carrier of the tropical diseases, chikungunya and dengue fever.

This mosquito, the Aedes albopictus, has already been found in 25 different countries in Europe but the UK has so far been spared as frosts kill the larvae and eggs.

However, health experts believe climate change will bring warmer and wetter rainfall which will create ideal conditions for the deadly mosquitoes.

Just a two degree rise in temperature could extend the creature’s geographical spread by 30 per cent according to a new report in Lancet Infectious Diseases which goes on to state that the UK should be on guard against the invasion.

“We are not suggesting that climate change is the only or the main factor driving the increase in vector-borne diseases in the UK and Europe, but that it is one of many factors including socio-economic development, urbanisation, widespread land-use change, migration, and globalisation that should be considered,” said Professor Steve Leach, from the emergency responses department at Public Health England.


Steve Leach says climate change is one factor in mosquito migration


“Lessons from the outbreaks of West Nile virus in North America and chikungunya in the Caribbean emphasise the need to assess future vector-borne disease risks and prepare contingencies for future outbreaks.”

There have already been outbreaks of chikungunya in France and Italy, malaria in Greece and the West Nile virus in Easter Europe. No human cases of the latter have been recorded in England so far despite the arrival of the carrier mosquito.

“Given the on-going spread of invasive mosquitoes across Europe, with accompanying outbreaks of dengue and chikungunya virus, Public Health England has been conducting surveillance at seaports, airports, and some motorway service stations,” said co-author Dr Jolyon Medlock.

“A better system to monitor imported used tyres, in which disease-carrying mosquitoes lay their eggs, needs planning.”

WHAT ARE THEY?

WHILE the word mosquito, which is Spanish for “little fly”, first became common in the 16th century, the insect has plagued humankind from the very beginning and even got a mention from Aristotle back in 300BC.

They are thought to have been around since the Jurassic period which makes the species about 210million years old.

Malaria accounts for much of human mortality from the bite of the mosquito but the insects also transmit many other fatal diseases, including yellow fever, lymphatic filariasis, Rift Valley fever, several types of encephalitis and the aforementioned dengue fever, chikungunya and West Nile fever.

Despite everything that science can throw at them mosquitoes persist, with their viruses and parasites quickly evolving to become immune to drugs and pesticides.


Female mosquitoes need blood proteins for their eggs


Globalisation has helped their spread with used tyres being a typical mode of transport as the tyres trap rainwater which becomes a breeding ground for bacteria that thrive in the heat absorbed by the rubber.

Tyre exports, particularly, are thought to be behind the exponential growth of dengue fever which has increased thirtyfold since 1965, according to World Health Organisation figures.

There are more than 3,500 species of mosquito although only a fraction of them can be deadly to humans.

In all the species it is only the females that bite humans as they need the protein in blood to help their eggs develop. A mosquito can drink up to three times its body weight in blood although it would take around 1.2m bites to drain the blood from one human body. They do not have teeth but use a serrated proboscis to pierce the skin.

Females can give male mosquitoes a hard time, locking so tightly together when they are mating that the males can often only get away by leaving their sex organs behind.

Yet just a moment of mating will allow a female to produce all the fertile eggs she will ever lay – up to 300 at a time. Eggs are laid in clusters, called rafts, in as little as an inch of stagnant water.

Considered to be the deadliest “animal” in the world the malaria-carrying mosquito alone kills more than one million people annually, most of them in Africa. Alexander the Great is believed to have been one of its victims in 323BC.

HOW CAN YOU WARD THEM OFF?

MOSQUITOES are attracted to humans by the smell of their sweat which releases the chemical octenol. Trying to mask the smell with perfume will not work however as they like that too.

Lemon-eucalyptus oil has been proven to be a smell they do not like as is picaridin and Deet. A product containing 10 per cent Deet has been shown to give protection for up to one-and-a-half hours.

Mosquitoes also like dark clothing as it retains more heat than light-coloured clothing and the insects like a bit of warmth.

Sadly, insect zappers have been found to be useless against them as research has shown that these kill more harmless insects such as moths than mosquitoes or other biting insects. Less than one per cent of mosquitoes are killed by the contraptions so have no real effect on mosquito numbers. Scientific testing has also shown that electronic repellers have very little effect.

As they need standing water to breed, removing these sources can help but insecticides have a very limited effect with insects returning once the chemicals have worn off.

Efforts to stop their global spread are having little result and climate change means that they may become even more of a nuisance in Scotland than even the midge.