Milan, 2.9. (Adnkronos Salute) – What is behind the increase in West Nile cases seen in parts of Italy like Padua and Veneto this year? Surveillance eyes are always on the mosquitoes where the virus is spreading lest new vectors arrive. Will it be so? For the moment, the Korean mosquito is exonerated (pending proof to the contrary). Feared because of its resistance to cold, they first saw it in 2011 in the province of Belluno, then intercepted it elsewhere, for example in Trentino, and it is not new to Switzerland either. neighbor. At the end of 2021, a team of scientists from the State University of Milan collected numerous pieces of evidence of its presence in Lombardy, where it seems to be settling rapidly, especially in the foothills of the province of Bergamo (so much that among the hypotheses it was admitted that by plane ‘ arrived via Orio al Serio’).
But this time, she is not the “defendant” in the West Nile case. “In Italy – explains Adnkronos Salute Sergio Zanzani, researcher at the University of Milan, expert in veterinary parasitology from the Department of Veterinary Medicine and Animal Sciences – there is enough evidence to confirm that West Nile transmission occurs through a autochthonous vector, the mosquito, which has always existed in Italy and which bites man: the ‘Culex pipiens’, a complex of species. It is the mosquito that we always had before the arrival of the tiger mosquitoes and which bites in the evening and at night”. While in relation to Korean, “so far, field data from those who have seen Aedes koreicus in areas of West Nile seem to place little importance on this new species. Evidence of the spread of West Nile virus in areas where Koreicus is present does not appear to support its significant vectorability,” he says.
And then the cold-loving mosquito, on which a beacon has been shining for some time, would have an “alibi”. The Korean buzzing insect “has gradually spread through our country, but it seems to be more of a spread in the pre-Alpine plains, from a mosquito originating in colder and adapted climates – affirms Zanzani – rather at the West Nile site. If the study is also this year in the lower Po Valley”. In other words, the Korean would be stationed elsewhere. It is the native “colleagues” who continue to “transfer West Nile to Italian territory” this year. “Culex pipiens is a competent vector, so there is nothing new on that front. Aedes albopictus, the real name of the tiger mosquito “which colonized Italy permanently and extensively”, does not seem to be a good vector capable of transmitting this virus. And even the most recent sightings appear to have nothing to do with West Nile. »
These new mosquitoes, continues the expert, “mainly affected the northeast: Aedes koreicus, which first settled in the province of Genoa, now includes the canton of Ticino, the province of Como, the province of Sondrio from the arc where they reached the province of Bergamo and closed the province of Trento and the provinces of Triveneto. But the distribution of the Korean mosquito with that of the West Nile does not correspond very well. Therefore, one must look at the mosquito native. Finally – he smiled. – Mosquitoes are a typical product of the Po Valley”.
Is it possible for others to become carriers of this virus? “At the moment, this cannot be said with certainty – warns Zanzani – they had done very rigorous scientific work on this subject in Switzerland. They had concentrated in particular on Aedes japonicus, “the Japanese mosquito,” which arrived from Slovenia and Austria, in the region of Friuli and probably also towards the West will gradually spread. When in Switzerland they saw that it landed on their territory, without knowing if it was suitable as a vector, they started experimental tests and tried to eliminate these mosquitoes to infect when they saw if they might transmit the pathogen and yes, they saw that this mosquito might be a competent vector, so now they know that if the West Nile virus appeared in Swiss territory, they might have a competent vector and even something to worry regarding. »
On the Koreicus “this type of work has not yet been done. Now it has also arrived in Switzerland, among other places I believe it is now spreading from the canton of Ticino to other cantons, to more central areas of the country. It might therefore be – concludes the researcher – that the same vector competence verification tests are also carried out on this new invasive species, and this would provide us with objective scientific data “on their capabilities”.
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