A Preliminary Study on The Effect of a Concurrent Infection with Eperythrozoon wenyonii on The Development of Theileria annulata in Calves1

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