Development of Theileria parva (Theiler, 1904) in the gut of Rhipicephalus appendiculatus (Neumann, 1901)

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Abstract
The life-cycle of Theileria parva in the gut of the tick Rhipicephalus appendiculatus was investigated in Giemsa-stained smears and in wet preparations under the phase-contrast microscope. The different developmental stages of T. parva were seen in a large proportion of specially-selected R. appendiculatus tickes. After the intra-erythorcytic merozoites were engorged by the ticks during a blood meal, the following development was observed. (1) In the lumen of the gut of infected nymphs, spindle-shaped microgamonts developed out of the ring-forms. These broke up into several thread-like microgameters after nuclear division and development of thread-like cytoplasmic projections. The ring-froms developed into round-forms of 3–4 μm in diameter which are considered to be macrogametes. (2) From the 6th day after repletion, zygotes with a clear zone in the centre appeared in the epithelial cells of the tick's gut. A steady increase in size and a progressively denser cytoplasm were observed up to the 3rd day after moulting to adult ticks. (3) Subsequently a slightly angular, retort-like stage developed by invagination inside the rounded zygotes, and from the 5th day after moulting this stage developed further into a club-shaped kinete. The kinetes propelled themselves in the gut by active gliding movements.