Theileria parva life cycle. In the animal host, the sporozoites attach to and enter lymphocytes, and develop into forms
called schizonts, which infects, multiplies and transforms the white blood cells (lymphocytes or macrophages, for T. parva and
T. annulata respectively) becoming blastoid cells (or lymphoblasts), responsible for disease pathology. Some of the schizonts
develop into merozoite forms, which are released from the lymphoblasts into the bloodstream, where they invade erythrocytes
and develop into forms called piroplasms. As Rhipicephalus appendiculatus ticks feed on animals infected with the parasite,
they ingest erythrocytes containing the piroplasms, which are able to infect ticks. Once in the tick gut, the parasites
differentiate into male and female gametocytes, which fuse to form zygotes. The zygotes differentiate into kinetes, which
move to the salivary gland and enter a particular cell type. The sporozoites are introduced into a mammalian host along with
tick saliva when the tick feeds, initiating a new cycle of parasite development. Transmission of T. parva is strictly trans-stadial
as the parasite is transmitted only by the nymphal and adult stages after acquiring infections as feeding larvae or nymphs.
Although T. annulata has a similar life cycle, it is exclusively transmitted by Hyalomma spp. adult ticks and infects
macrophages in the mammalian host.