Infection of Mammalian Erythrocytes by the Avian Malaria Parasite,Plasmodium lophurae . ∗

Abstract

Reports concerning attempted infection of mammals with avian malaria parasites are limited, although recently Beckman obtained negative results following introduction of Plasmodium cathemerium parasites into man 1 and the guinea pig. 2 In a series of experiments unrelated to the immediate problem, the author noted that guinea pig erythrocytes injected into normal 10 day chick embryos survived for a period of 4 days. As a result of this finding, it was decided to investigate the possibility of securing infection of mammalian cells in chick embryos infected with P. lopkurae, a parasite to which chick embryos have been found to be highly susceptible. 3

White leghorn embryos of 10 days′ incubation were given intravenous injections of 3 × 10⁷ parasites, representing the 24th passage of P. lopkurae in embryos. Two tenths cc each of twice washed erythrocytes of mouse, rat, rabbit, dog, sheep, and man were injected intravenously into embryos on the 2nd day after parasite introduction, at which time the infections averaged about 1100 per 10,000 avian erythrocytes. Blood films were usually made twice daily thereafter, although in certain embryos 4 or 5 smears were made in a 24 hour period. Giemsa's stain was used. Only cells agreeing in size, morphology, and staining reactions with the mammalian cell introduced were considered in determination of infection, since during the later stages of embryo infection artifacts arose which might have led to false identification.

Dog and rabbit erythrocytes were not well adapted to survival in chick embryos, the former killing the embryo in a period of 12 hours, the latter disintegrating rapidly. Sheep and rat red blood cells were well preserved even after 3 days but were uninfected. Guinea pig cells, although surviving better than those of the rabbit, disintegrated to the point that they were difficult to separate from abnormal avian erythrocytes.