Immunohistological evaluation of feline herpesvirus-1 infection in feline eosinophilic dermatoses or stomatitis

This study used immunohistochemistry (IHC) and histopathology to evaluate the presence of feline herpesvirus-1 (FHV-1) in feline cases of 'eosinophilic granuloma complex' (EGC) or other eosinophilic dermatoses or stomatitis, diagnosed at the Veterinary Pathology Diagnostic Service, University of Sydney between January 1996 and June 2008. Two of the 30 cases (6.6%) examined showed positive immunoreactivity to FHV-1 using IHC. Intranuclear inclusion bodies were also detected on histopathological examination of haematoxylin and eosin stained sections of both cases but were very difficult to find. Therefore, FHV-1 is uncommonly associated with EGC or other eosinophilic dermatoses or stomatitis in Sydney. However, misdiagnosis as an EGC lesion or other eosinophilic dermatoses may occur if inclusion bodies are overlooked or absent on histopathology and this may significantly decrease the chance of a favourable treatment outcome. FHV-1 should be considered in cats with severe ulcerative cutaneous or oral lesions, unresponsive to corticosteroid treatment, with or without concurrent or historical signs of upper respiratory tract or ocular disease more typical of FHV-1. IHC may be helpful in differentiating FHV-1 dermatitis or stomatitis from other eosinophilic lesions, which is of vital clinical and therapeutic importance.