Leishmania in the Chick Embryo. I. Multiplication of Amastigotes of L. donovani in the Liver*

SYNOPSIS. On the 14th day of incubation chick embryos were inoculated intravenously with approximately 4 × 104 amastigotes of Leishmania donovani in ground, infected hamster spleen. Embryos were then incubated at 28, 33, or 37 C. At 1 hr and at 2, 4, and 6 days postinfection embryos were killed, and parasite burdens in the liver and spleen estimated by the method of Stauber. The spleen played a relatively minor role in clearance of amastigotes from the bloodstream and parasites did not survive beyond the 2nd day. In each experiment ∼20% of the injected amastigotes were found in the liver after 1 hr. Numbers of amastigotes declined in embryos incubated at 37 C and were not observed later than 2 days postinfection. At 33 C the amastigotes multiplied at a rapid rate, and at 28 C they not only multiplied but, in some instances, transformed to the promastigote form.