| dc.description.abstract | Studies were conducted on the haemoprotozoal parasites Theileria
annulata, Theileria parva and Babesia bovis-maintained in stationary
cultures of bovine erythrocytes.
The effect of different factors on the growth in vitro of T.
annulata was evaluated. These factors included concentrations and
methods for the preparation of bovine erythrocyte suspensions, reduced
oxygen tensions, complex tissue culture media, sera, medium
supplements and bovine aortic endothelial, monolayers. In repeated
experiments with two strains of T., armulatag intraerythrocytic multiplication
occurred by division into quadruplet forms. Transmission
electron microscopic studies showed that quadruplet forms resulted
from schizogony and that these parasites had the ultra structural features
of merozoites.
The number of erythrocytes with four T. annulata merozoites,
identical to the quadruplet form seen in cultures, increased during
the initial parasitaemic rise in two splenectomized carrier calves
and in two splenectomized calves that had been inoculated with parasitized
erythrocytes. Analysis of the incidence and distribution of
parasitized erythrocytes in the calves indicated that intraerythrocytic
division into four was the primary mode of multiplication for T. annulata.
A simple technique for the in vitro isolation of peripheral
blood lymphocytes was tested and proved to be more sensitive than
standard diagnostic techniques for detecting the persistence of the
intralymphocytic schizonts of T. annulata in chronic carrier cattle.
Light and transmission electron microscopic studies showed that
in stationary erythrocyte cultures, j. parva multiplied by the same
schizogonous process as T. annulata, to form four intraerythrocytio
merozoites. In T. parva, cultures a maximum of 20-3(y/o of the parasitized
erythrocytes contained quadruplet, forms by day 6-10 in vitro
whereas an incidence of 40-600% was seen in comparable cultures of
T. annulata. Failure of T. parva, and T., annulata merozoites to reinvade
erythrocytes in vitro prevented the establishment of continuous
cultures.
Continuous cultures of two B. bovis isolates, from Mexico and
South Africa, were established and the. effect on, parasite growth of
different complex media and concentrations of sera was evaluated.
An invasion assay was used, to compare the in vitro infectivity for
fluorescein-stained erythrocytes of B. bovis,. Z. axmulata and T. Parva
merozoites.
Studies on the incorporation of tritiated nucleic acid precursors
by B. bovis in vitro showed that the purines, hypoxanthinev adenosine,
adenine and gmanosine were incorporated to a greater extent than the
pyrimidines, uridine and cytidine. There was no apparent uptake of
thymidine by either of the two B. bovis isolates in vitro. | en |
