Electron microscopy and histopathological examination of canine papilomavirus

Abstract

Diagnosis of canine papillomavirus (CPV) infection by histopathology, transmission and scanning electron microscopy is presented. The study is based on data obtained by examining nonregressing papillomas (warts) from naturally infected dogs with clinical manifestations of CPV infection. Papules on the mouth and lips were common bilaterally in all dogs. Confirmatory diagnosis of sick dogs was made by clinical findings, histopathology, transmission and scanning electron microscopy. Histopathological examination of hematoxylin and eosin stained papillomas revealed lymphoplasmocytic cell infiltration and fibrosis, parakeratosis in the dermis, papillary proliferation and intranuclear vacuole degeneration in the stratum spinosum. Electron microscopy demonstrated viral icosahedral capsid formation and non-enveloped viral structure of CPV. Transmission electron microscopy demonstrated viral particles and virions in the nuclei of infected cells, viral crystal mode formation in the nucleus. Scanning electron microscopy demonstrated virions and virus-like particles budding in the infected tissue. The findings of the study reveal that electron microscopy and histopathology are effective and sensitive methods in the diagnosis of CPV infection. Electron microscopy is the only imaging technique that allows direct visualization of viruses, along with affected tissues and cells, due to its nanometer-scale resolution. This study reveals the intracellular and extracellular viral pathogenesis, viral ultra structure and structural components of CPV. Present findings indicate canine papillomavirus causes canine papillomatosis, inclusion bodies are common in nonregressive infection, papillomavirus induces cytopathic effect and pathogenesis, viral particles located in the cell and forms crystal mode in nuclear space.