Encephalitis

During August and September thousands of horses in fields and race tracks in many parts of the U.S. drooped their necks, banged their heads against the ground, tried to run on their sides, collapsed on the turf. In Massachusetts alone 200 horses died, victims of equine encephalomyelitis. Entirely different are the eastern and western varieties of this disease, although both are caused by viruses which attack the brain and spinal cord, produce inflammation, high fever, and in some localities 100% mortality. Last spring Dr. Ralph Walter Graystone Wyckoff of Lederle Laboratories at Pearl River, N.Y. and Dr. Joseph Willis Beard of Duke University prepared vaccines from chicken embryos which conferred immunity against both types of the disease, and this summer as many as 50,000 doses of the vaccine were shipped daily to all parts of the country.

More puzzling to physicians than the remarkable intensity of equine encephalomyelitis this year were a few scattered cases of encephalitis ("sleeping sickness") among children on farms in southwestern Massachusetts. Encephalitis, or inflammation of the brain, is ordinarily not widespread in the U. S. Its last large epidemic occurred in St. Louis in 1933. Cause of the disease is a virus of which little is known. Its most prominent symptoms are high fever, headache, delirium, restlessness or lethargy, double-vision, paralysis or involuntary jerking of fingers, arms, legs. Unpredictable are its after-effects which may include "parkinsonian mask," (complete absence of facial expression), insanity, sexual perversion, tremors and tics of all types.

Top-flight Boston physicians began at once to investigate the relation of human encephalitis to equine encephalomyelitis, and last week, in the New England Journal of Medicine, Dr. LeRoy Dryden Fothergill and associates* announced that, for the first time, from a case of human encephalitis, they had isolated a virus which was identical with the eastern strain of equine encephalomyelitis virus. A few days later, in Science, Pathologists Leslie Tillotson Webster and F. Howell Wright of Manhattan's Rockefeller Institute confirmed the findings of the Boston physicians and described four similar cases.

The method of identifying the virus was simple: suspensions of brain tissue taken from fatal human cases were injected into the brains of young Swiss mice. Two days later the mice showed "ruffled fur, slowing of activity, alternating with convulsive twitchings," and other symptoms similar to those of equine encephalomyelitis.

Some were killed and samples of their brain tissue were injected into other healthy mice, which fell sick in two days and died. The virus also worked on monkeys, guinea pigs, rabbits. Typical of eastern equine encephalomyelitis was the two-day incubation period, as well as the violent symptoms which are unique and completely different from those occurring in human beings. As a further check, however, they injected deadly doses of the virus into animals which had been immunized against eastern equine virus. All these remained "perfectly well."

Next experiments will probably test the power of Dr. Wyckoff's chick vaccine to confer immunity on human beings. Further research may also determine whether some equine virus is responsible for a large proportion of human encephalitis.

*John H. Dingle, Sc.D. and Drs. Sidney Farber and Marion Lee Connerley.

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