The viruses of both the Eastern and and Western strains of equine encephalomyelitis have definitely been proven to be pathogenic to animals other than horses. White mice, guinea pigs, pigeons, white rats, rabbits, monkeys, sheep, goats, ducks, dogs, pigs, cats, hens and the European hedgehog have all been infected with Eastern strain, whereas Western strain virus failed to infect sheep, pigs, dogs, cats, and the European hedgehog, but it did produce the disease in the other animals mentioned. The infection was artificially started by means of intracerebral inoculation of infected brain tissue. Both strains have been found to produce encephalitis in man through natural infection.