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. 2021 May 7;14(1):243.
doi: 10.1186/s13071-021-04736-z.

West Nile and Usutu viruses co-circulation in central Italy: outcomes of the 2018 integrated surveillance

Paola Scaramozzino  1 , Andrea Carvelli  2 , Gianpaolo Bruni  1 , Giuseppina Cappiello  3 , Francesco Censi  4 , Adele Magliano  1 , Giuseppe Manna  1 , Ida Ricci  1 , Pasquale Rombolà  1 , Federico Romiti  1 , Francesca Rosone  1 , Marcello Giovanni Sala  1 , Maria Teresa Scicluna  1 , Stefania Vaglio  5 , Claudio De Liberato  1
Affiliations

West Nile and Usutu viruses co-circulation in central Italy: outcomes of the 2018 integrated surveillance

Paola Scaramozzino et al. Parasit Vectors. .

Abstract

Background: West Nile (WNV) and Usutu (USUV) are emerging vector-borne zoonotic flaviviruses. They are antigenically very similar, sharing the same life cycle with birds as amplification host, Culicidae as vector, and man/horse as dead-end host. They can co-circulate in an overlapping geographic range. In Europe, surveillance plans annually detect several outbreaks.

Methods: In Italy, a WNV/USUV surveillance plan is in place through passive and active surveillance. After a 2018 WNV outbreak, a reinforced integrated risk-based surveillance was performed in four municipalities through clinical and serological surveillance in horses, Culicidae catches, and testing on human blood-based products for transfusion.

Results: Eight WNV cases in eight equine holdings were detected. Twenty-three mosquitoe catches were performed and 2367 specimens of Culex pipiens caught; 17 pools were USUV positive. A total of 8889 human blood donations were tested, and two asymptomatic donors were USUV positive.

Conclusions: Different surveillance components simultaneously detected WNV only in horses and USUV only in humans and mosquitoes. While in endemic areas (i.e. northern Italy) entomological surveillance is successfully used as an early detection warning, this method in central Italy seems ineffective. To achieve a high level of sensitivity, the entomological trapping effort should probably exceed a reasonable balance between cost and performance. Besides, WNV/USUV early detection can be addressed by horses and birds. Further research is needed to adapt the surveillance components in different epidemiological contexts.

Keywords: Co-circulation; Culex pipiens; Italy; Surveillance; Usutu virus; West Nile virus.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Location of WNV/USUV positive and negative holdings during 2018 surveillance activities in central Italy
See this image and copyright information in PMC

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MeSH terms

Supplementary concepts