Impact of the invasive Asian Tiger Mosquito in the Algarve

Although it arrived in Portugal in 2017, the impact of the Asian tiger mosquito, a species capable of transmitting diseases such as dengue, zika or chikungunya, is still unclear.

“The species was found in Portugal in 2017 for the first time. In the Algarve [in Loulé] and in Penafiel we don’t know if they happened by coincidence or not, but there shouldn’t be much difference, since they were still very localized outbreaks at the time”, José Manuel Grosso-Silva, curator of entomology at the Museum of Natural Sciences History and Sciences of the University of Porto, says Lusa.

It is not yet known how it arrived in the Algarve, but the introduction to Penafiel, in the district of Porto, seems to have taken place thanks to a retreading company, which imported tires with eggs of this mosquito deposited in the water left inside the tires.

“Mosquitoes have aquatic eggs, females lay eggs in water, and eggs develop in water. Tires, stored in heaps, accumulate water inside and provide a place which, d ‘on the one hand, has water and bacteria and therefore food for mosquito larvae, and then has no predators,’ explains the specialist.

The entomologist, who holds a doctorate from the Faculty of Sciences of the University of Porto, adds that there is still “no information on the wide distribution of the species from this point” where she has identified with Penafiel, specifying that it “is neither a good nor a bad sign”, it happens because “it hasn’t been that long”.

Spread across the country

Even so, he claims that “it is more likely that the species will spread, as has happened in Spain”, not least because, “either in the type of place where it was found in the Algarve, or in the tires of Penafiel, there are no predators”.

From then on, “they spread, multiply and spread”, in the northern region “much more easily, due to greater water availability, and even due to climatic hazards”.

As for the impact that the introduction of this mosquito has on ecosystems, Grosso-Silva says that “it is still not possible to give a definitive answer”, but “it is very certain that it causes discomfort and some sort of wildlife disturbance.” , because they do not only feed on human blood, females bite different warm-blooded vertebrates, so it is very likely that they feed on several species as well.

The Asian tiger mosquito arrived in Europe via Albania in 1979, and since then it has been detected in several countries, such as Italy, France and Spain.

Transmitted Disease

It is capable of transmitting diseases such as dengue, zika and chikungunya, as well as filarial parasites, but “the health problem itself is not a problem unless several conditions are combined”, underlines the biologist.

“They are here, but the diseases they transmit are not there. They had to find an infected person at the right time to bite and become carriers themselves. There must be, inside the body of the mosquito, the evolution of the parasite, and it will bite the next person able to transmit it. It is therefore not a guaranteed thing that a mosquito which bites an infected person will then transmit, ”he explains.

For “the transmission of the disease to be inevitable”, there must be “a lot of mosquitoes and a lot of people”.

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