Experiments with the Virus of Yellow Fever in Marsupials, with Special Reference to Brown and Grey Masked Opossums

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  • Villavicencio Field Laboratory, Villavicencio, Colombia


  1. 1.The virus of a Colombian strain of yellow fever was maintained in the brown masked opossum (Metachirus nudicaudatus) for 10 consecutive passes by the intramuscular inoculation of serum.
  2. 2.There was no apparent increase in virulence or infectiousness of the virus for the brown masked opossum or for the related grey masked opossum in the course of these passes. The virus seemed equally infectious for Saimiri monkeys both before and after serial passage in the brown masked opossum.
  3. 3.The grey masked opossum (Metachirops opossum) was found to be resistant to infection with the strains of yellow fever virus tested; circulating virus was recovered from only 1 of 28 animals.
  4. 4.Brown masked opossums which failed to show circulating virus after inoculation with small but demonstrable doses of virus sometimes circulated virus after a 2nd inoculation with the same or different strains of virus. Animals that had circulated virus once failed to show a 2nd circulation of virus on reinoculation.
  5. 5.Antibody response, as measured by the intracerebral protection test, was usually regular in the brown masked opossum, but a few sera seemed to give “false reactions” and a somewhat larger number of sera failed to show protective power even though taken from animals that had circulated virus.
  6. 6.The results of the intracerebral protection tests with sera of the grey masked opossum seemed to be completely unrelated to exposure of the animals to the virus of yellow fever.
  7. 7.Serum of the grey masked opossum was found to be highly toxic for mice on intracerebral inoculation, killing about 40 per cent of the mice; serum of the brown masked opossum did not show this toxic property.
  8. 8.The evidence available with regard to the possible role of these marsupials in the epidemiology of jungle yellow fever is inconclusive.