Usutu Virus Detection In Abruzzo Region, Italy: The Entomological Surveillance As Key Tool For The Mosquito-Borne Disease Prevention

Purpose: Usutu (USUV) and West Nile (WNV) viruses (genus Flavivirus, family Flaviviridae) are emerging zoonotic agents whose natural transmission cycles usually involve ornitophilic mosquitoes and avian hosts. USUV and WNV appeared in Italy in 1996 and 1998, respectively. Aiming to early detect arbovirus circulation and to reduce the risk of infection in humans, several National surveillance programs have been put in place by the Italian Ministry of Health since 2002. The one health philosophy has been adopted in designing all these plans in which synergism, collaboration and an increasing degree of integration between human and animal health sectors are clearly evident. In these surveillance plans, humans, animals and mosquitoes are monitored. This report described the first evidence of USUV circulation in Abruzzo region (Italy), as result of the integrated surveillance activities. Methods & Materials: Between June 2016 and May 2018, 56 mosquito collections were performed in the “Ospedale Civile Santo Spirito”, Pescara municipality, Abruzzo region, in collaboration with the local health authorities. Adult mosquitoes, collected by using Bg-Sentinel traps, were identified by morphology, the females sorted in 412 pools and tested for Chikungunya, Usutu, West Nile and Zika viruses by Real Time RT-PCR assays. Results: Overall, 19,066 mosquitoes were collected. Four genera were identified and Culex pipiens was the most abundant species (n. 6,505). When tested for the presence of arboviruses, 3 pools of Cx. pipiens resulted positive to USUV. Conclusion: Although its presence has been demonstrated in several Italian regions, this is the first report of USUV circulation in Abruzzo. Being probably introduced by migratory birds which may act as reservoirs of many zoonotic mosquito-borne flaviviruses including USUV and WNV, the repetitive positivities found in the mosquito pools stand for the establishment of an enzootic cycle between native birds and local bird feeding mosquitoes. Culex pipiens can feed both on humans and birds and is known to be the main vector of flaviviruses in Italy. So far no circulation of USUV has been reported among humans and animals, however following the USUV detection the entomological monitoring was strengthened, moreover vector control measures and monitoring in humans and animals were set up to prevent human infection.