Abstract

Promastigotes of Panamanian strains of Leishmania mexicana and L. braziliensis were inoculated intravenously into 14-day chick embryos. The course of infection was followed by examination of liver impression smears prepared from embryos incubated at 28, 33, and 35°C for 1 hour and 1, 2, and 4 or 6 days post-infection. Parasites of each species declined in numbers rapidly at 35°C. Parasites multiplied more rapidly at 28 than at 33°C, and greater numbers of parasites were observed in the liver after 4 days of incubation at 28°C than after 6 days at 33°C. Multiplication of the two Leishmania species was similar at 28 and 33°C, respectively. Morphologically, L. braziliensis in the liver of chick embryos was more compact and stained more intensely than L. mexicana. Although L. mexicana was generally pale-staining and swollen in appearance, the parasites were viable as demonstrated in cultures initiated with infected liver. Promastigote and amastigote forms were observed in embryos incubated at 28°C, while no flagellum was seen on forms at 33°C.