PROGRESS IN PROTOZOOLOGY

2.32 I. CUNNINGHAM
throcytic schizogony in cells of the lymphoid system; Babesia multiply
exclusively in their intraerythrocytic piroplasm form.
The cultivation of Theileria spp. dates from 1945 when Tchernom
o r e t z reported the growth of Koch bodies (schizonts) of T. annulata
in explants of infected calf spleen placed in drops of calf plasma clots
in chick embryo extract and Tyrode's salt solution enriched with various
growth-promoting compounds. About twenty years lapsed before the
next step of major significance in Theilerial cultivation was recorded.
Using Theileria-iniected cells growing on monolayers of baby hamster
kidney cells (B.H.K.), Hulliger et al. (1964) observed the mode of
multiplication of the macroschizont in the host cell and demonstrated
that parasite and host cell division was interdependent. A few years
later successful cultivation of T. parva which causes East Coast Fever
of cattle in East Africa, was described by Malmquist et al. (1970).
Using the techniques developed for the cultivation of T. annulata
and T. parva, it is now possible to isolate and grow lymphoblastoid cell
lines infected with most of the Theilerial species in which schizonts
have been described. These include T. lawrenci grown in the cells of
buffalo and cattle, T. taurotragi in eland and bovine lymphoid cells and
T. hirci in ovine lymphocytes. Cultures of these parasites can be initiated
from either schizont-infected lymphoid cells or by in vitro infection
and transformation of normal lymphocytes by sporozoites of
Theileria obtained from infected ticks. Establishment of successful cultures
in which 90-100% of the lymphoid cells contain theilerial macroschizonts
provides an excellent model of parasite-host cell interdependence.
These cultures are handled in a manner similar to that used for
human lymphoblastoid cell lines isolated from patients suffering from
benign or malignant lymphoproliferative disorders.
Methods for the cultivation of Babesia, on the other hand, confined
to the piroplasm stage within the erythrocyte have only recently been
developed. The efforts were undoubtedly stimulated by the reports
of the successful cultivation of the erythrocytic stages of human malaria
(T r a g e r and Jensen 1976). More recently significant progress
has been achieved in the cultivation of Babesia bovis. In two distinct,
yet related approaches, piroplasms of this important parasite have been
grown in bovine erythrocytes in spinner flasks (Erp et al. 1978) and in
microaerophilous stationary culture (Levy and Ristic 1980).
Although it is 35 years since the first isolation of Theileria in culture,
only one stage in its complex life cycle can be grown predictably
in vitro. It is hoped that the impetus provided by the cultivation of
malaria and Babesia will produce a system able to support the propagation
of the intraerythrocytic piroplasm forms. This perhaps might lead
to the production of gametocytes and thus the completion of the verte-
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