As site of the bite. The incubation period

As mentioned in section 1.2.2, a characteristic of the pathogenic Theileria spp. parasites
is their ability to cause a cancer-like disease in the mammalian host, a unique feature among eukaryotic parasites. The species that transform host cells in to a cancer-like phenotype are T. parva, T. annulata, T. taurotragi, and T. lestoquardi. It has to be noted though, that Theileria transformed cells revert back to the apoptotic cell cycle once treated with anti-theilerial drugs. As ticks infected with T. parva feed they inject sporozoites into the host. These parasites, localize and multiply in the lymph node that drains the site of the bite. The incubation period is 8–12 days with schizonts spreading to other lymph nodes. They are similarities clinical signs of East Coast fever and tropical theileriosis and these include high fever sometimes up to 42 °C because of the formation on numerous schizonts inside the lymphocytes which rapture,
accompanied by heavy swellings of the lymph nodes and the spleen. During this phase high death rates may occur (Mizikar 2018). The other symptoms are depression, drooling, lacrimation, diarrhoea, anorexia, and weight loss, as well as decreased milk production. Petechiae and ecchymoses occur in the conjunctiva and oral mucous membranes. Blindness because of corneal opacity is also commonly observed. Severe pulmonary oedema with dyspnoea and a frothy nasal discharge is common and terminal in many animals, whereas others become prostrate and comatose. In T. parva infections erythrocytic schizogony is rare or absent but in the life cycle of T. annulata it is present. In tropical theileriosis since the parasites rapture the red blood cells, icterus, anaemia, and occasionally haemoglobinuria are observed. T parva and T. annnulata parasites cause impairment of capillaries in the CNS leading to a fatal condition called “turning sickness” cite. Sporozoites, of tick origin, invade and infect host lymphocytes and macrophages. Cell entry occurs through receptor mediated parasite-directed phagocytosis. Infected lymphocytes are transformed in vitro into lymphoblastic cells (Shaw 2003). Macroschizonts develop in the cytoplasm of the transformed cells and then divide synchronously with the host lymphocytes to infect their daughter cells.


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