Experimental Herpetic Encephalitis Produced by Feeding Herpes Virus to Guinea Pigs.

Herpetic encephalitis may be produced in rabbits by inoculating such animals either subdurally, intravenously, subcutaneously, or intraperitoneally. The possibility of inducing herpetic encephalitis in guinea pigs by feeding occurred to us. While there is little evidence to support the view that epidemic encephalitis in man is caused by the herpes virus, any evidence regarding the portals of entry of this virus into the animal body is important. Nothing is known concerning the portal of entry of the true virus of epidemic encephalitis and epidemiological control of the disease is based largely upon speculation. It is known that paralysis follows the inoculation of the virus of poliomyelitis into the stomach and intestines of monkeys and it seemed probable to us that infection might be produced in this way with the herpes virus.

Four guinea pigs were fed by catheter 3 cc. of a freshly prepared emulsion of herpetic (Beckley) rabbit brain. One guinea pig received 4 cc. while a 6th received 5 cc. Of the 6 guinea pigs so treated 3 died. The animals which had received 4 cc. and 5 cc. of herpes emulsion respectively died on the 8th day following feeding. One of the guinea pigs which had received 3 cc. of the herpes emulsion by mouth died on the 10th day. The other 3 guinea pigs remained unaffected.

The brains of the 3 guinea pigs which died were removed and emulsions were prepared. Rabbits inoculated with these emulsions subdurally developed typical symptoms of herpetic encephalitis and died of the disease. Cultures prepared from the brains of the guinea pigs and inoculated rabbits were without growth. The herpes virus passed through guinea pigs by way of the gastrointestinal tract and then passed back to rabbits appears to be some-what attenuated at first but quickly regains its virulence. For example the virus recovered from the brain of the guinea pig which had received 5 cc. of herpes emulsion by mouth required 9 days to produce a fatal encephalitis in the first rabbit tested.