Electron microscopy of equine respiratory viruses in organ cultures of equine fetal respiratory tract epithelium.

: Organ cultures of equine fetal tracheal and nasal turbinate epithelium were inoculated with equine influenza virus-A1 (EIV-A1), equine herpesvirus-1 (EHV-1), or equine rhinovirus-1 (ERV-1). Infected organ cultures were processed for scanning and transmission electron microscopy at various intervals and were compared with noninfected controls. Organ cultures inoculated with ERV-1 appeared normal with the exception of rare island-like lesions in infected nasal turbinate. Virus particles were not seen in thin sections of organ cultures infected with ERV-1. The EHV-1 caused extensive loss of the epithelial layer in tracheal and nasal turbinate organ cultures. The classic stages of herpesvirus morphogenesis were seen in thin sections of organ cultures infected with EHV-1. The EIV-A1 caused a scattered loss of cilia that was only apparent in infected tracheal organ cultures. Cilia were also seen bound in bundles. In thin sections, EIV-A1 particles were seen budding from the bases of microvilli.