Armstrong – Table of Contents

failed to convey the disease to monkeys by means of nasopharyngeal washings, spinal
fluid and blood; however, he thought this was not surprising, suggesting not the absence
of virus from these fluids, but that the susceptibility of monkeys to the infectious agent
was low.
Armstrong’s group tried to transmit the disease to other laboratory animals but
was able to accomplish this only in white mice. Dr. Leslie T. Webster (9) of the
Rockefeller Institute for Medical Research had spent many years breeding special strains
of mice to use for virus isolation and transmission of neurotropic viruses. Using autopsy
tissue from the St. Louis encephalitis epidemic sent to him by Armstrong and colleagues,
Webster was able to establish infection by intracerebral inoculation in a strain of his
laboratory-bred mice. When he informed Armstrong and colleagues, they were able to
establish infection from second monkey passage brain emulsion regularly in stock white
mice by intracerebral inoculation. The two strains of virus isolated in the separate
laboratories were identical. The use of mice reduced the need for large numbers of
expensive and irascible monkeys, and it expedited the further investigation of the
infectious agent. Attempt to pass the agent to rabbits were unsuccessful.
The pathology of infection was similar in human cases, monkeys and mice. At autopsy
the brains were usually markedly congested (“blood shot”). Accumulation of round cells
around the blood vessels (perivascular cuffing), destruction of nerve cells in the brain and
upper spinal cord, and focal collection of inflammatory cells in the brain characterized
the histological features.
Since mice were more easily infected and susceptible to infection than monkeys,
subsequent studies made use of mice to investigate the characteristics of the virus (9, 10).