West Nile Virus (WNV): An integrated animal-human-vector plan applied in Sicily in 2016

Abstract

Background: West Nile disease (WND) is a vector-borne zoonosis caused by a virus of the Flavivirus genus (family Flaviridae), transmitted through mosquito bites (primarily Culex genus). In Sicily, the first outbreak of WNV infection was reported in August 2010 in province of Trapani. Since 2001, a National Surveillance Plan for WNV, based on wild bird mortality and on entomological and sentinel animal surveillance has been developed. An integrated national plan of imported and autochthonous human WNV and Usutu disease, was issued in 2016, in order to develop a network between human and veterinary surveillance. In September 2016, a human case of neuroinvasive WND, with symptoms of encephalitis and meningitis, was confirmed in a 38-year-old man from Trapani, by serological evaluation on serum and liquor. The subject, recovered from illness, referred to have spent his holiday in Santo Domingo in August 2016. The authors describe the application of the integrated plan in this human WND case. Methods & Materials: According to the surveillance plan, sera and blood samples from 11 horses, 271 chickens and two dogs were collected around the residency of the human clinical case. The entomological monitoring was performed on mosquitos collected in 8 selected sites, within 1 km from the same residency. IgM and IgG ELISA assays were performed on sera. Blood and mosquito samples were tested by Real-Time RT PCR to detect the presence of WNV lineage 1 and 2. Results: The most of the mosquitoes caught belonged to Aedes albopictus, Culex pipiens, Culex hortensis, and Culiseta langiareolata. Two dogs and two horses showed positivity for WNV IgG. The other samples were negative by serological and molecular assays. Conclusion: The results of the animal and entomological surveillance did not show any active WNV circulation during the period object of this study. The IgG seropositivity in a few samples suggested a remote WNV presence. Integration of surveillance and monitoring activities was important to indicate that human case was not autochthonous and the man could have been infected abroad, during the holiday spent in the Caribbean.