In order to discover the nutritional requirements of an intracellular parasite one must grow it axenically, apart from all other living cells, in a medium susceptible ultimately to chemical analysis. Such cultivation has not yet been achieved for any intracellular parasite, but some progress has been made with the erythrocytic stages of the bird malaria parasite Plasmodium lophurae.
Methods. The organism is maintained in 2- to 3-week-old ducklings by the passage once weekly of appropriate amounts of infected blood. For passage ducklings the dosage is such as to produce high parasitemia on the 6th to 7th days with death usually on the 8th day. Ducklings to be used as donors for the cultivation experiments receive a higher dosage so that they show a parasitemia of around 80–100 parasites per 100 red blood cells on the 4th day after inoculation.
The Rockefeller Institute, New York 21, New York. Supported in part by grant E-3550 from the National Institute of Allergy and Infectious Diseases.