Preliminary report on the observation of a coronavirus in the intestine of the laboratory rabbit.

Intestinal infections are a major cause of mortality in domestic rabbits. Although a few pathogenic organisms have been associated with this type of infection, it is often impossible to demonstrate the presence of any etiologic agents. Recently viral particles were observed in the intestine of diseased rabbits submitted to our laboratory for diagnosis. A study was then initiated to evaluate the presence of viral agents in the intestine of rabbits showing clinical signs of enteritis. Viral particles with morphological characteristics of the Coronaviridae family were observed by electron microscopy in most specimens of fecal material obtained from sick rabbits. Such particles were not seen in the feces of healthy animals. These particles, which have a density of 1.07-1.18g/cm3 on sucrose gradient, hemagglutinate rabbit red blood cells. Furthermore this virus has some antigenic relationship with the human coronavirus 229-E since immune serum to this virus blocks the hemagglutination of the rabbit erythrocytes. Antibody titers to this virus were detected in rabbit sera obtained from colonies with a high incidence of intestinal infections. When fecal material containing coronavirus particles were inoculated on various tissue culture systems, no cytopathic effects were observed.