Negative contrast electron microscopic techniques for diagnosis of viruses of veterinary importance.

Negative contrast electron microscopy (NCEM) was utilized as a routine tool in the diagnosis of viral infections of domestic and wild animals. Viruses identified by this technique were observed in infected culture systems or clinical specimens from several species including horses, cattle, sheep, dogs, cats, pigs, deer, Rocky Mountain bighorn sheep, antelope, and several avian species. Viruses were identified by NCEM based on their size, morphology, and symmetry and consisted of adenoviruses, herpesviruses, paramyxoviruses, myxoviruses, picornaviruses, parvoviruses, coronaviruses, reoviruses, rotaviruses, and poxviruses. Mixed populations were also readily demonstrable by this technique: the most common mixed infections consisted of coronaviruses and rotaviruses, and picorna- or parvo-viruses with coronaviruses, rotaviruses, herpesviruses, or adenoviruses. Immunoelectron microscopy was also used to serotype viral agents present in the specimens examined. Viruses identified by this technique were bovine rotaviruses, coronaviruses, and herpesviruses, and bovine and equine adenoviruses.