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A Preliminary Study on The Effect of a Concurrent Infection
with Eperythrozoon wenyonii on The Development
of Theileria annulata in Calves1
M. S. Al-Khalifa, G. M. Khalil, H. S. Hussein and F. M. Diab
Zoology Department, College of Science P.O. Box 2455, King Saud University,
Riyadh 11451, Kingdom of Saudi Arabia
Abstract
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This work investigates the effect of concurrent calf infection with E.
wenyonii on T. annulata development. In group I, calves simultaneously were
inoculated with both parasites, E. wenyonii parasitaemia appeared 7 days
post-inoculation (PI), peaked (62 peryth./rbc) 21 days PI and disappeared 31
days PI. T. annulata parasitaemia appeared 28 days PI, peaked (87%) 35 days PI
and disappeared 50 days PI. T. annulata parasitaemia in calves infected only
with T. annulata (control) appeared 15 days PI and peaked (90%) 30-35 days PI
when the calves died. In group II calves, inoculated with E. wenyonii first,
parasitaemia appeared one week PI, peaked (65 eperyth./rbc) 21 days PI and
disappeared 35 days PI. Parasitaemia of T. annulata, inoculated 2 weeks later,
appeared 25 days PI, reached a low peak (27%) 45 days PI and disappeared 65 days
PI. After splenectomy (AS) of groups I and II calves, E. wenyonii parasitaemia
reappeared 15 days AS, peaked (52 eperyth./rbc) 29 days AS and disappeared 57
days AS. T. annulata parasitaemia reappeared 27 days AS, reached a low peak
(42%) 47 days AS and disappeared 87 days AS. Group I and II calves survived AS.
In group III, calves, inoculated with E. wenyonii 5 days after the appearance of
T. annulata parasitaemia (15%), T. annulata developed as in the control group
and all calves died before E. wenyonii development. Alteration of T. annulata
development may be attributed to modulation of the host immune system and/or
competition with E. wenyonii for a certain substrate.
Keywords: Concurrent infections, Eperythrozoon wenyonii, Theileria annulata,
blood parasites, calves.
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