PROGRESS IN PROTOZOOLOGY

2.32 I. CUNNINGHAM
Large scale cultures grown by the method of T r a g e r and Jensen
(1980) can produce sufficient yields of parasites for biochemical
and immunological studies. Microcultures, on the other hand, have been
used to screen for drug sensitivity and to test for growth inhibiting
antibodies.
The asexual erythrocytic forms of malarial parasites cannot transmit
the infection in nature; when ingested by a mosquito they are killed
and digested. However, certain merozoites can develop within erythrocytes
into male and female gametocytes. On ingestion by an appropriate
mosquito, they form male and female gametes which unite and initiate
the sporogenic cycle of development in the vector. Remarkable progress
has been made in the in vitro production of gametocytes infective to
mosquitoes (T r a g e r and Jensen 1978, Jensen 1979) making
available for experimental use the sporozoites and the entire sporogenic
cycle of P. falciparum.
In mammalian malaria, the sporozoites ingested by the mosquito give
rise to a single cycle of development in hepatic cells of the liver. The
merozoites formed in this pre-erythrocytic cycle seem to be capable only
of initiating the erythrocytic cycle. Recently the pre-erythrocytic cycle
of rodent malaria, P. berghei, has been obtained in vitro by inoculation
of sporozoites into various types of tissue culture (Strorae et al.
1979). The most successful cultures were obtained in a human embryonic
lung cell line (H o 11 i n g d a 1 e et al. 1981) in which large schizonts
formed 48 h postinoculation with sporozoites, and the merozoites infective
to mice were present at 72 h.
Conclusions
The presentations at this Symposium have demonstrated the continued
progress in the cultivation of parasitic protozoa. Methods are
now available to cultivate most of the forms found in the mammalian
hosts and vectors, but gaps remain to be filled with regard to culture
methods for some stages and species of Malaria, Piroplasmida and salivarian
trypanosomes. It is likely that before the next Congress this goal
will be achieved and thus lead to a better understanding of the parasites.
REFERENCES
Anderson S. J. and Krassner S. M. 1975: Axenic culture of Trypanosoma
cruzi in a chemically defined medium. Exp, Parasitol., 61, 144-145.
Aila J. L., Bretana A., Casanova M. A., Avila A. and Rodriguez F.
1979: Trypanosoma cruzi: Defined medium for continuous cultivation of
virulent parasites. Exp. Parasitol., 48, 27-35.
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