Abstract
It was reported previously 1 that hamsters, when allowed to feed upon St. Louis encephalitis virus, either die with encephalitis, or develop an immunity as evidenced by appearance of serum antibody and resistance to intracerebral inoculation. Subsequent tests have indicated that hamsters, fed Japanese encephalitis virus react in. much the same way. The present report describes the extent of the infection in hamsters following feeding with St. Louis (Hubbard strain) and with Japanese (Nakayama strain) encephalitis viruses, as determined by subinoculation of mice with various tissues.
The possibility of infection by way of the alimentary tract with neurotropic viruses, other than those of poliomyelitis and encephalomyelitis of mice, has received some attention. Infection of mice by introduction of St. Louis virus into the alimentary tract has been described by 2 groups of investigators, 2 , 3 and both report development of immunity in survivors. The latter group also fed 2 hamsters with St. Louis virus and found neutralizing antibody some days later. 4
In our experiments hamsters were induced to eat virus by starving them overnight, and offering them the heads of infected mice. Tissues to be tested for virus were carefully removed from exsanguinated animals with separate sets of instruments, emulsified in a minimum quantity of broth to which 10% normal sheep serum had been added, centrifuged, and the supernatant inoculated into 3 or 4 mice each. In the case of bacterially contaminated tissues such as the intestine, the specimens were washed repeatedly in sterile physiological saline and were thereby rendered sufficiently free of bacteria to allow intracerebral inoculation.
In most of the experiments a second intracerebral passage to mice was made with the brain tissue of any mouse found ill or dead, in which there was doubt concerning the cause.
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