Plasmodium paranucleophilum n. sp. from a South American Tanager *

SYNOPSIS. The avian malaria parasite described in this paper was isolated from a South American tanager of uncertain species, somewhat tentatively identified as belonging to the genus Tachyphonus. It is believed to have come from northern Brazil. Because the erythrocytic stages are, except for minor differences, similar to those of Plasmodium nucleophilum it is proposed to call it P. paranucleophilum. The chief difference separating the 2 species is the appearance of phanerozoites of the new species in lymphocytes of the circulating blood; these are characteristically vacuolated and give rise to moderate numbers of merozoites, probably in most cases 50 or less. Strains of P. nucleophilum isolated from other passerine birds also produce phanerozoites parasitizing lymphocytes, but such cells have never been observed in the blood stream. A subspecies, P. nucleophilum toucani , which we isolated from a Swainson's toucan Ramphastos swainsonii , also produces phanerozoites invading lymphocytes but it is less selective; endothelial cells of the brain are heavily attacked. It is also very lethal to canaries, whereas passerine strains of P. nucleophilum are usually quite benign. P. paranucleophilum , if the strain we have isolated is typical, lies between the 2 in pathogenicity, causing marked anemia but seldom death.