Abstract
Summary
Two-day-old chicks, after inoculation with St. Louis encephalitis virus, subdurally or by other routes, failed to show any clinical evidence of infection. Nevertheless, the brains of chicks which had been inoculated subdurally proved infectious for mice in a dilution of 10-2 for at least 6 days and sometimes in a dilution of 10-1 up to 20 days. Histological sections of such brains showed only slight changes, consisting at most of small areas of perivascular infiltrations.
The virus was carried through nine serial passages at 3- to 4-day intervals in the brains of 2- to 6-day-old chicks. Chick brains of the ninth serial passage showed areas of focal, diffuse and perivascular infiltration.
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