In vitro and in vivo Cultivation of the Virus of Rift Valley Fever

That viruses may be cultivated successfully through many generations is being increasingly found as new ones are being submitted to the process of cultivation. The method now widely employed for securing cultures in vitro is that devised by Li and Rivers 1 for vaccine virus. A similar device introduced by Goodpasture, 2 of the chorio-allantoic membrane of the developing chick, may be regarded as an example of cultivation in vivo quite distinct from the ordinary multiplication which occurs in the course of usual infection in developed, susceptible animal species. Just as it had previously been shown that herpes virus grown in tissue culture and in chick embryo may be titrated in the brain of mice, 3 it has now been shown that it is possible to cultivate and titrate, in the ways indicated, the virus of Rift Valley fever of sheep.

Dr. G. M. Findlay kindly supplied the material with which the cultivations were begun. It consisted of the liver of a mouse in the 86th passage. We owe indeed to Dr. Daubney and Dr. Findlay 4 the discovery of the virus nature of Rift Valley fever.

In vitro Cultures. The medium employed consisted of Tyrode solution to which minced 10-day-old chick embryo was added. The Rivers' flasks contained 4.5 cc. of this medium, and to each was added 0.2 cc. of a Berkefeld filtrate of a 10% phosphate buffer emulsion of infected mouse liver. The titration was made by inoculating 0.2 cc. of a dilution of a culture intraperitoneally into mice. Two series of cultures, I and II, were run. Series I was carried through 11 and Series II through 12 generations.