Drosophila C virus: experimental study of infectious yields and underlying pathology in Drosophila melanogaster laboratory populations.

The underlying pathology of a nonhereditary virus, the Drosophila C virus, was studied. This study was related to the contamination routes (ingestion or contact) and developmental timing. When oral contamination occurred at the first larval instar: (1) the flies were contaminated, (2) the flies which had developed the most rapidly were the most infected, (3) in newly emerged females, the level of virus was higher than in newly emerged males, (4) when infected flies were reared on virus-free medium only males lost their virus. Moreover, oral contamination of adults was very efficient, but the highest virus yield was obtained when both larvae and imagos grew on virus-contaminated medium. About 30 to 50% of the flies died on the sixth day. They were as DCVC invaded as DCVC-injected flies. It seemed that when the virus yield was higher than a given threshold, all flies died, whatever had been the contamination routes. When contaminated adult females and virus-free males were reared together on a virus-free medium, females could infect males. In contrast, contaminated males were not able to infect virus-free females. Thus, only females were able to contaminate a rearing medium or other flies.