Propagation of Variola Virus in the Developing Egg

Since the early reports of Goodpasture and his coworkers 1 , 2 , 3 the chorio-allantoic membrane of the developing chick has been used for the propagation of a number of filterable viruses. This paper reports the propagation of the virus of variola major isolated directly from the pustular content of an active case. It is now in the forty-fifth consecutive passage on the chorio-allantoic membrane of the developing egg. The propagation of alastrim 4 has been attempted only after 2 passages through Macacus rhesus monkeys.

The patient, an unvaccinated white woman aged 32, developed a typical case of confluent smallpox shortly after a visit to Mexico City. The material for propagation was removed from lesions on the lower leg and soles of the feet on the seventeenth day after the onset of the disease. The abdominal and back lesions were starting to peel at this time. The material was obtained from 4 or 5 vesicles by means of a 1 cc. tuberculin syringe and consisted of 0.3 cc. of slightly turbid fluid and some swabs moistened with vesicle fluid. Growth was first obtained in one egg inoculated with 0.1 cc. of the vesicle fluid. Four days after inoculation, about 20 discrete yellowish white lesions were observed on the membrane. Impression smears showed typical Paschen bodies with Morosow's stain. 5 The same findings were noted in the second egg, 5 days after inoculation with 0.1 cc. of a saline suspension of the swab material. The usual shell-flap method of Goodpasture was used throughout. Passage was made every 4 to 5 days by transferring a piece of membrane about 1 mm. in diameter, containing 2 or more lesions, to the exposed membrane of a 11–13 day egg.