An Epidemic of a Severe Pneumonitis in the Bayou Region of Louisiana: VI. A Comparative Study of the Viruses of Lymphogranuloma Venereum, Psittacosis, and Louisiana Pneumonitis

Abstract

The virus of Louisiana pneumonitis was compared to psittacosis and meningopneumonitis viruses. Complement-fixation tests indicated that the agent belonged to the psittacosis-lymphogranuloma venereum group of viruses but could not be differentiated by this means from other members of the group. It was shown that 80% or more of mice injd. subcut. with the virus of Louisiana pneumonitis succumbed, while a much smaller proportion of mice infected by these routes with either psittacosis or meningopneumonitis virus developed fatal infections. Mice were equally susceptible to infection with the new agent when measured dilutions of the virus were administered either intracerebrally or intra-peritoneally. There was, however, a marked variation in tropism when the agents of psittacosis or meningopneumonitis were tested in mice. Guinea pigs developed a fatal febrile illness when inoculated intraperit. with Louisiana pneumonitis virus and a febrile, non-fetal illness when either psittacosis or meningopneumonitis virus were given by the same route. There was no evidence that the serum of humans recovered from infection caused by this agent or of animals inoculated with living or dead antigens prepd. from materials containing this agent possessed antibodies which could protect mice or guinea pigs from infection with the virus. Mice and guinea pigs immunized with formalin-killed vaccines prepd. from yolk sacs infected with Louisiana pneumonitis virus were subsequently found to be resistant to infection with Louisiana pneumonitis virus. Animals given similar vaccines prepared from yolk sacs infected with either psittacosis or meningopneumonitis virus failed to develop resistance against infection with Louisiana pneumonitis virus.