Plasmodium brasilianum in the common marmoset Callithrix jacchus.

Chronic quartan malarial infection has been established in the common marmoset (Callithrix jacchus). Plasmodium brasilianum from a douroucouli monkey (Aotus trivirgatus) was used to infect splenectomized twin animals, passed to an intact animal, and then to 4 other intact adults, 2 pairs of twins. In 2 of the 4 latter animals there was continuing patency with parasitaemias of less than or equal to 0.5% parasitized erythrocytes for 30 weeks. The other 2 had lower initial levels of parasitaemia; in 1 of these parasitaemias remained low or subpatent. All marmosets developed lymphocytosis. One animal became ill 30 weeks after infection with anaemia, weight loss and mild proteinurea, the other 3 remained well. Histological examination showed minor changes in the kidneys; spleens of infected animals showed marked follicular hyperplasia and phagocytosis of pigment. The livers showed sinusoidal hypercellularity and pigment deposition and in splenectomized animals, a marked lymphoid follicular hyperplasia in the portal tracts.