Isolation of a Virus from Infectious Bovine Kerato-Conjunctivitis

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Abstract
A virus has been isolated from biopsy material from eyes of cattle with acute infectious bovine keratoconjunctivitis. No serum samples from these animals were available for testing against the virus. The virus is cytopathogenic for cells of bovine and human origin; ether resistant; relatively heat labile; does not hemagglutinate red blood cells from chickens, mice, hamsters, guinea pigs, rabbits, bovines, sheep, or man. Fluorescence microscopy of infected cells stained with Coriphosphine O and studies on the influence of 5-BUDR, 5-FUDR, and 5-FU on virus multiplication indicate that it is a DNA virus. Antisera (bovine or rabbit) against enteric, respiratory and other bovine viruses have failed to neutralize cytopathogenic activity of the virus. Per-nasal instillation of virus-containing tissue culture fluids has induced classical infectious bovine kerato-conjunctivitis of varying degrees of severity in 8 out of 18 inoculated cattle. It is of interest that 7 out of 12 heifers have failed to respond clinically and immunologically to inoculation of the virus which may be due to failure of inoculation rather than to immunity as pre-inoculation serum samples had no neutralizing antibodies. Sera from animals with experimentally induced acute kerato-conjunctivitis have neutralized the cytopathic effect of the virus. Electron microscope studies have demonstrated that the virus induces nuclear changes of a type not previously described in tissue culture cells infected with any known virus. Recent electron microscope studies(9) of infectious pustular vulvovaginitis virus (IPV) and IBR virus in tissue culture have confirmed previously published studies on IBR virus (10,11). There appears to be a similarity in particle size and structure between these viruses and the agent isolated from eyes of cattle with IBKC. However, there appears to be a difference between nuclear changes observed in cells infected with the agent isolated in the present study (formation of whorls, see Fig. 7) and those observed in cells infected with IBR (10,11) and IPV (9). The findings indicate that this virus might be causatively related to acute infectious bovine kerato-conjunctivitis (“pinkeye”), should further animal inoculation studies confirm these preliminary observations.