Monitoring West Nile virus (WNV) infection in wild birds in Serbia during 2012: first isolation and characterisation of WNV strains from Serbia

T Petrović,E Escribano-Romero,D Lupulović,M Kapetanov,S Lazić,D Fabijan,J C Saiz,A B Blázquez,G Lazić

doi:10.2807/1560-7917.es2013.18.44.20622

Abstract

West Nile virus (WNV), a neurovirulent mosquito-transmissible zoonotic virus, has caused recent outbreaks in Europe, including Serbia from August until October 2012. Although humans can be infected, birds are the main natural WNV reservoir. To assess WNV circulation in northern Serbia, 133 wild birds were investigated. These comprised resident and migratory birds, collected between January and September 2012 in the Vojvodina province. The birds belonged to 45 species within 27 families. Blood sera (n=92) and pooled tissues from respective birds (n=81) were tested by enzyme-linked immunosorbent assay (ELISA), plaque reduction neutralisation test (PRNT) and real-time reverse transcription-polymerase chain reaction (RT-qPCR). WNV antibodies were detected in seven (8%) sera: four from Mute Swans (Cygnus olor), two from White-tailed Eagles (Haliaeetus albicillas), and one from a Common Pheasant (Phasianus colchicus). Five sera neutralised WNV but not Usutu virus. For the first time in Serbia, WNV RNA was detected by RT-qPCR in pooled tissue samples of eight respective birds. WNV RNA was also derived from an additional bird, after a serum sample resulted infective in cell culture. The total nine WNV RNA positive birds included three Northern Goshawks (Accipiter gentilis), two White-tailed Eagles, one Legged Gull (Larus michahelis), one Hooded Crow (Corvus cornix), one Bearded Parrot-bill (Panarus biramicus), and one Common Pheasant. Phylogenetic analysis of partial E region sequences showed the presence of, at least, two lineage 2 Serbian clusters closely related to those responsible for recent human and animal outbreaks in Greece, Hungary and Italy. Full genomic sequence from a goshawk isolate corroborated this data. These results confirm WNV circulation in Serbia and highlight the risk of infection for humans and horses, pointing to the need for implementing WNV surveillance programmes.

Highlights

West Nile virus (WNV) a neurovirulent mosquito-transmissible Flavivirus is maintained in nature in an enzootic transmission cycle between birds and mosquitoes
Of 92 wild bird sera tested, seven (8%) were IgG enzyme-linked immunosorbent assay (ELISA) positive (Table). They belonged to three species: four Mute Swans; two White-tailed Eagles (Haliaeetus albicilla; Accipitriformes); and one Common Pheasant (Phasianus colchicus; Galliformes)
Table West Nile virus surveillance results on wild migratory and resident birds sampled in the province of Vojvodina, northern Serbia, January–September 2012

Summary

Introduction

West Nile virus (WNV) a neurovirulent mosquito-transmissible Flavivirus is maintained in nature in an enzootic transmission cycle between birds and mosquitoes. WNV infections have been described in a wide variety of vertebrates, birds are the main natural reservoir. In Europe, the reported seroprevalence in birds has been generally low, 1 to 10%, being usually higher among migratory than resident birds [2,3,4,5,6,7,8]. This leads to suggest that migratory birds may play a pivotal role in spreading WNV infection. Some studies pointed to resident birds as important in maintaining WNV circulation in nature [9,10]

Objectives

Methods

Results

Conclusion