West Nile virus and Usutu virus in wild birds from Rescue Centers, a post-mortem monitoring study from Central Italy.

Abstract

West Nile virus (WNV) and Usutu virus (USUV) are mosquito-borne flaviviruses causing world-wide numerous cases in animals and humans. In Italy, both viruses have been associated with neurological diseases in humans and wild birds. Wild bird rescue centers where support in emergency and care of diseased animals are provided, are potential significant hot spots for avian infection surveillance, as recognized in the Italian Integrate National Surveillance Plan for Arboviruses. Here we report the results of a post-mortem active monitoring study conducted from November 2017 to October 2020 on animals hosted in five wild bird rescue centers of Central Italy. Five hundred seventy-six (n = 576) wild birds were tested by real-time polymerase chain reaction (RT-PCR) for the presence of WNV or USUV RNA fragments. No birds tested positive for USUV RNA (n = 0; 0.00 %). Evidence of WNV RNA (Ct value = 34.36) was found in one bird (n = 1; 0.17 %), an adult little grebe (Tachybaptus ruficollis subsp. ruficollis), that tested WNV positive on December 2019 and died due to traumatic injuries. The main pathological findings consisted in mild CD3+ lymphocytic tubulo-interstitial nephritis, meningoencephalitis, and cardiomyocytes loss and interstitial oedema of the heart. This study highlights the strategic role of wildlife rescue centers in monitoring both the introduction and circulation of avian emerging zoonotic diseases. Also, the presence of WNV during the cold season evidences the possible role of birds in overwintering mechanisms in the Italian territory and requires further investigations.