Ultrastructural Evidence for the Viral Etiology of Feline Infectious Peritonitis

Filtration studies indicate that the causative agent of feline infectious (fibrinous) peritonitis is less than 200 m μ in smallest dimension. Viral particles 94 m μ in diameter, within and budding into the endoplasmic reticulum of the mesothelial cells in areas of inflammation, were found by electron microscopy and may be the etiologic agent. No bacterium or mycoplasma was cultured from peritoneal exudate, nor identified in affected tissues.