Studies with an unclassified virus isolated from diarrheic calves

Abstract

A transmissible agent (Breda agent) was isolated from a calf with diarrhea and shown to be infectious by inoculation orally into gnotobiotic and conventionally reared calves. The "Breda" agent had the morphology of a virus and possessed a hemagglutinin. Antigenic studies showed the virus to be antigenically different from bovine coronavirus, parainfluenza 3 virus, bovine rotavirus, bovine parvovirus and bovine pestivirus (BVD). Attempts to culture the virus in cell or organ cultures or in embryonated eggs, were unsuccessful. The virus was either spherical or kidney shaped, with 7-9 nm peplomers on the surface. A few particles possessed coronavirus processes of 17-20 nm, but these were arranged irregularly and were thought to be tissue debris. Three out of eight experimental calves developed severe diarrhea and the lesions in the small and large intestines were similar to those reported for coronavirus. The virus replicated in the jejunal and ileal regions of the small intestine and in the spiral colon, as judged by immunofluorescence. The virus multiplied in all experimental calves and was excreted in the feces; excretion correlating with the onset of diarrhea or a change in the appearance of the feces. There was little or no malabsorption measured by the uptake of D-xylose and the fact that infection of both the crypt and villus epithelial cells was observed, suggests that the pathogenesis may be different from rotavirus and coronavirus. Fourteen of forty seven calves in the outbreak were infected with the virus, virus was not identified in other farm outbreaks of the disease.

A Morphological Study of the Replication of Breda Virus (Proposed Family Toroviridae) in Bovine Intestinal Cells

“…Cytoplasmic IF was generally scattered throughout the cell, with a few discrete areas of intense intracytoplasmic IF. The overall pattern of immunofluorescent staining in Breda virus-infected tissues was consistent with that in an earlier report (Woode et al, 1982).…”

“…Histopathological lesions in calves GC58 and GC63 were the same as those previously described for calves infected with Breda virus serotypes 1 and 2 (Mokresh, 1984;Pohlenz et aL, 1984;Woode et al, 1982Woode et al, , 1985. In the mid and posterior small intestine there was villous atrophy, and enteroabsorptive cells were squamous or cuboidal rather than columnar.…”

“…Virus was identified in diarrhoeic faeces of the infected calves by the haemagglutination methods and negative stain electron microscopy (EM) described previously (Woode et al, 1982).…”

“…Breda virus is a recently described agent causing diarrhoea in newborn calves (Woode et al, 1982). While Breda virus bears superficial similarities to coronaviruses, there are significant morphological and antigenic differences between the two (Woode et al, 1982).…”

“…While Breda virus bears superficial similarities to coronaviruses, there are significant morphological and antigenic differences between the two (Woode et al, 1982). Two serotypes of Breda virus have been described (Woode et al, 1985); both cause diarrhoea and infect the intestine from mid-jejunum posteriorly through the descending colon, causing villous atrophy and necrosis of villus and crypt epithelial cells.…”