Carriers of tropical fevers already in Europe

(ORDO NEWS) — Scientists warn: there is a risk that in the coming decades mosquitoes – carriers of dengue, chikungunya, Zika and other dangerous tropical infections will reach Southern and Eastern Europe and North America. This, in turn, will cause epidemics of rare diseases. And the blame for everything is global warming.

Between man and animal

In 2015, British and American researchers examined how female mosquitoes select their intended prey. Several dozen insects were placed in a special device – a chamber with two tunnels connected to it. Two people simultaneously thrust their hands into them, after which the flaps were opened, and mosquitoes flew towards the smell of prey.

It turned out that if genetically identical twins are involved in the experiment, the insects are evenly distributed between the two volunteers. But in the case of fraternal twins – their DNA matches only 50 percent – the bulk of the mosquitoes rushed to only one.

The authors of the work suggested that the choice of insects is influenced by the set of genes that a person inherited at birth. Which ones, it is not known – most likely, producing substances that attract or scare off bloodsucking.

However, much depends on the mosquitoes themselves. Not all representatives of the subspecies Aedes aegypti – namely, their scientists used in experiments with twins and twins – feed exclusively on human blood.

Researchers from Princeton University (USA) collected Aedes aegypti eggs at 27 locations throughout sub-Saharan Africa – both in densely populated cities and where there are very few residents. Then they raised adult mosquitoes and selected only females: females feed on blood, and plant sap is enough for males. And then they repeated the experiment of 2015, only the guinea pig played the role of a twin: a human hand was placed in one tunnel, and a rodent in the second. Unexpectedly, most of the insects preferred the animal.

The rest – representatives of several West African populations – showed no obvious preferences. Interestingly, the choice correlated with the number of people living within a radius of 20 kilometers from the egg collection site. Urban mosquitoes, in contrast to their rural counterparts, liked human blood more.

In addition, the volunteer’s hand was more often chosen by individuals who were bred from eggs collected in arid areas, where the amount of precipitation is highly dependent on the season. The researchers suggested: most likely, five to ten thousand years ago, it was the unfavorable climate that forced mosquitoes to settle near human habitation, because there is always water there, which increases the chances of reproduction. And the blood of Homo sapiens is apparently an added bonus.

Therefore, even today, most mosquitoes still prefer animal blood. However, scientists warn: by 2050, populations of these insects in different parts of Africa will switch exclusively to the “human” diet. This means that dangerous infections will spread faster.

Fever like a European

Scientists’ interest in Aedes aegypti – it is also called the yellow fever mosquito – is understandable: it is the carrier of dengue, chikungunya, Zika virus and yellow fever. The birthplace of the insect is Africa. Today it lives in all tropical regions, but, judging by the forecasts of experts, it will soon go on the offensive to the north.

So, in April last year, at the Congress on Clinical Microbiology and Infectious Diseases, experts warned: due to global warming, tropical diseases will appear in many European countries. And already in August, experts from the European Center for Disease Prevention and Control recorded three cases of Zika virus infection in France: it was an infection through a mosquito bite near the city of Hyères.

These data are cited from January 1, 2007 to April 13, 2016 in a new report from the World Health Organization.

The researchers suggested that the main suspect, Aedes aegypti, did not make it to France. His distant relative, the tiger mosquito Aedes albopictus, was declared the culprit: it also carries the Zika virus. The insect lives in southern Europe, but, according to American scientists, in the next 30 years it will populate more northern regions. Experts do not exclude that by 2050 the yellow fever mosquito Aedes aegypti may take a liking to Europe and North America.

Experts from the University of Liverpool are inclined to the same conclusions. According to them, global warming in the coming decades may trigger an outbreak of Zika fever in Eastern Europe.

Climate in favor of mosquitoes

Russian scientists also note: due to climatic changes, the habitats of mosquitoes carrying tropical infections are shifting to the north. This means that in the coming years, Russians are at risk of facing these diseases as well.

For at least the past ten years, cases of West Nile fever have been reported in the Astrakhan and Volgograd regions, and the Aedes species – carriers of dengue and Zika virus – live in Sochi. True, there is not enough warmth, so mosquitoes cannot infect a person.

However, there is a possibility that everything will change, – Swedish and German scientists warn about this. Viruses such as chikungunya are capable of replicating rapidly in the body of a mosquito. Conditions are relatively high ambient temperatures during the day and no prolonged drought.

This is the climate that will be established in Europe and North America by 2100, if the average global temperature rises by about 4.6 degrees Celsius – according to the authors of the work, this is the most likely scenario. It is possible to avoid it, but to do this, the fight against warming must be started now.


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