First neuroinvasive human case of West Nile Disease in Southern Italy: Results of the 'One Health' approach

Background West Nile Disease (WND) is a zoonotic mosquito-borne infection involving viral pathogens, human and animal hosts, vectors and environment. Cooperation among medical, veterinary and entomological fields has been promoted by the Italian Public Health Authorities, and an integrated West Nile Virus (WNV) Surveillance Plan has been in force in Italy since 2016 to prevent the transmission risk of WND to humans through an early detection of viral circulation by animal and entomological surveillance. This managing model is unique in Europe. Objectives This survey aimed at presenting the 'One Health' approach applied in 2016 to the first autochthonous human case of West Nile Neuroinvasive Disease (WNND) in Sicily (Southern Italy). Methods Serological (anti-WNV IgM and IgG ELISA, anti-WNV neutralizing antibodies) and molecular tests were conducted on blood, liquor and urine of a 38-year-old man with encephalitis and meningitis. Overall, 2704 adult culicides from 160 mosquito catches were morphologically identified. Female mosquitoes were analysed in pools for WNV RNA detection. Serological (anti-WNV IgM and IgG ELISA) and molecular analyses for WNV were carried out in 11 horses, 271 chickens and two dogs sampled in farms around the man's residence. Results and conclusions WNND was confirmed by serological analysis on patient's liquor and serum. Collected mosquito species included Culex pipiens (93.56%, CI95% 92.64%-94.49%), Aedes albopictus (5.25%, CI95% 4.41%-6.09%), Culex hortensis (0.59%, CI95% 0.30%-0.88%), Culiseta longiareolata (0.55%, CI95% 0.27%-0.83%) and Anopheles maculipennis s.l. (0.04%, CI95% -0.04% to 0.11%). Mosquito pools were negative for WNV RNA. Two dogs (100%) and two horses (18.18%, CI95% -4.61 to 40.97%) resulted positive for anti-WNV specific antibodies. The 'One Health' approach allowed to report the first human neuroinvasive WND in Sicily and to confirm the local circulation of WNV in animals of the same area where the clinical case occurred, defining the autochthonous origin of the infection.