Relationship Between Epidemic Keratoconjunctivitis and St. Louis Encephalitis Viruses

Summary It is impossible at present to distinguish epidemic keratoconjunctivitis virus from St. Louis encephalitis virus by means of the intracerebral neutralization test in mice. The sera from convalescent epidemic keratoconjunctivitis animals and from convalescent or hyperimmune St. Louis encephalitis animals neutralized epidemic keratoconjunctivitis and St. Louis encephalitis viruses to an equal extent. No differences could be elicited by performing neutralization tests with the keratoconjunctivitis virus that had been through 3 successive rabbit passages. Neutralization tests in which serum dilutions were used against a constant amount of virus also failed to show any differences between the 2 viruses. Considerable cross-neutralization was obtained with the related Japanese B and West Nile viruses. Infectivity tests in animals revealed that rabbits and guinea pigs were susceptible to intracerebral inoculation with keratoconjunctivitis virus but not to St. Louis virus.