Pathologic and immunohistochemical findings in eyes of flavivirus infected game birds

Abstract

[Introduction]: Flaviviruses such as West Nile virus (WNV) and Bagaza virus (BagV) have shown to be pathogenic for game birds such as red-legged partridges (Alectoris rufa) and common pheasants (Phasianus colchicus). WNV frequently produces photophobia in raptors and BagV infected birds show apparent blindness. Using immunohistochemistry and histology we studied ocular lesions and antigen distribution in red-legged partridges experimentally infected with WNV and in red-legged partridges and common pheasants naturally infected with BagV. [Material and methods]: Cross sections of eyes from euthanized or dead birds were examined microscopically. A polyclonal antibody against the envelope protein of WNV was used for antigen detection. [Results]: In both infections, inflammatory infiltrates were present in different parts of the eye, although pectenitis was only present in birds infected with BagV. In WNV infected partridges, viral antigen was detected in endothelial cells throughout the eye and in the rods and cones layer of the retina. BagV antigen was present in the endothelial cells of the pecten (only in partridges) and in different cells of the retina. [Discussion & Conclusion]: This is the first time that ocular lesions caused by WNV are described in gallinaceous birds. Detection of BagV antigen in the retina may be responsible for the apparent blindness observed.