1.Three hundred and thirty-five South American opossums, belonging to seven different species, were tested against several strains of yellow fever virus.
2.Didelphis marsupialis, Didelphis paraguayensis, and Metachirops opossum were found to be resistant to all of the virus strains used; very few opossums circulated virus, and, in general, the immunity response was poor. In addition, M. opossum was found to be resistant to intracerebral inoculation of French neurotropic virus.
3.Metachirus nudicaudatus and Marmosa incana were found to be susceptible to the virus strains employed. A great majority of the inoculated animals circulated virus, and nearly all of these developed a humoral immunity. However, M. nudicaudatus did not show any symptoms of encephalitis when inoculated intracerebrally with French neurotropic virus.
4.Marmosa cinerea and Caluromys philander were found to be partially susceptible to the virus strains used. Both species were resistant to the inoculation of the J.Z. virus strain but were found to be fully susceptible to the O.C. virus strain. C. philander, which failed to show circulating virus after injection of the J.Z. virus strain, promptly circulated virus when reinoculated with either the O.C. or the Asibi strain of virus.
5.Not only was it found that the individual species responded differently to the various virus strains employed, but also indviduals of the same species re acted in different ways to the strains of virus used.
From the Laboratory of the Serviço de Estudos e Pesquisas sôbre a Febre Amarela, Rio de Janeiro, Brazil.