Persistence of Brunhilde Poliomyelitis Virus in Rodent Brain without Evidence of Adaptation. ∗

Summary

Adaptation of Brunhilde virus to cotton rats or hamsters was not achieved by the method of alternation of passage between these animals and rhesus monkeys.

Brunhilde virus was found present in the brains of symptomless hamsters up to 5 days after intracerebral inoculation and up to 10 days after intracerebral inoculation of cotton rats and Swiss albino mice (no tests at longer intervals were made). There was no evidence of the virus persisting after more than one cotton rat or hamster passage, and there was no histological evidence of virus proliferation. This is highly suggestive that no multiplication had occurred in the brains of these animals. This persistence of virus in symptomless animals is similar to that observed by Smith (6) in attempts to establish St. Louis encephalitis in rats and guinea pigs.