West Nile And Usutu Circulation In Wild Birds From North-West Italy 2015-2018

Purpose: Wild birds represent the natural hosts and carriers of diverse zoonotic diseases, e.g. Avian FLU, zoonotic flavivirus encephalitis, chlamydiosis, deserving specific monitoring efforts from Public Health Institutions. Surveillance plans on wild animals are in place to early detect the occurrence of pathogens in the north western Italian region of Piemonte, including West Nile virus (WNV) and Usutu virus (USUV) findings. Methods & Materials: Migratory and resident wild birds found dead were collected by passive surveillance (Wildlife Plan). The West Nile Disease (WND) active Surveillance Plan on culled black crows, magpies and jays was scheduled since 2015 from july to november by trapping animals in wet areas. Central nervous system and a pool of lung, heart, spleen and kidney were analyzed separately for each animal. Upon viral RNA purification, samples were tested with Real-time one step RT-PCRs: one able to discriminate between WNV Lineage 1 and 2 and one specific for USUV. All positive samples were sent for confirmation to the OIE National reference Centre for WND in Teramo. Results: Between 2015 and March 2018, 2.666 wild birds were analyzed: 1.092 from the Wildlife Plan and 1.574 from the WND Plan. Positivities for WNV Lineage 2 were found in 13 wild birds: 1 eagle owl, 1 kestrel and three hooded crows in 2015, six hooded crows in 2016 and two in 2017. USUV was confirmed in two black birds in 2015, one from the Wildlife Plan and one from the WND Plan. From July to 20th August, 7 hooded crows, 2 magpies, one pheasant and a kestrel resulted infected with WNV Lineage 2. Moreover, 2 hooded crows, 3 magpies and a black bird were found positive to USUV. Conclusion: WNV Lineage 2 circulates in wild birds in Italy since 2011 and is the most frequently detected Lineage in Italy. In 2018 an increase in the WNV cases was registered in the summer in six out of eight provinces of Piemonte. As a consequence, all the prevention and control measures required by the Italian WND integrated surveillance plan were promptly activated to reduce the risk of infection for humans.