The horse, according to a recent report by Tyzzer and his co-workers1 of the Harvard Medical School, has only a minor part in the spread of equine encephalomyelitis; they suggest that the main proliferation and dissemination are by migratory birds.
Last September numerous pheasants and other wild birds were found dead or in a helpless paralytic condition in certain rural sections of Connecticut. Four moribund pheasants were sent to the Harvard Medical School for diagnosis. On account of the history of paralysis in these birds and the absence of gross lesions, brain emulsions were prepared and injected intracerebrally into Swiss mice. All mice thus injected died in from four to five days with symptoms similar to those observed in mice injected with the eastern type of horse encephalomyelitis. At necropsy the brain tissues of the mice were found to be bacteriologically sterile. Serial passage of the pheasant virus in
EQUINE ENCEPHALOMYELITIS IN BIRDS. JAMA. 1938;111(27):2493–2494. doi:10.1001/jama.1938.02790530047015