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Title: Theileria  
Author: World Heritage Encyclopedia
Language: English
Subject: Apicomplexa, Alveolate, Nyala, Hartebeest, Operation Flood, Elaeophora elaphi
Publisher: World Heritage Encyclopedia


Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Superphylum: Alveolata
Phylum: Apicomplexa
Class: Aconoidasida
Order: Piroplasmida
Family: Theileriidae
Genus: Theileria

Theileria annulata
Theileria electrophori
Theileria equi
Theileria microti
Theileria orientalis
Theileria parva

Theileria is a genus of parasitic protozoan that belongs to the phylum Apicomplexa and is closely related to Plasmodium. Two Theileria species, T. annulata and T. parva, are important cattle parasites.[1] T. annulata causes tropical theileriosis and T. parva causes East Coast fever. Theileria are transmitted by ticks.[2] The genomes of T. annulata and T. parva have been sequenced and published.[3][4]

Theileria equi is a known cause of equine piroplasmosis.[5]

Vaccines against Theileria are in development.[1][6] In May 2010, it was reported that a vaccine to protect cattle against East Coast fever had been approved and registered by the governments of Kenya, Malawi and Tanzania.[7]


Species in this genus undergo exoerythrocytic merogony in the lymphocytes, histiocytes, erythroblasts and other cells of the internal organs.

This is followed by invasion of the erythrocytes by the merozoites, which may or may not reproduce.

When merogony does occur no more than four daughter cells are produced.

The frequent occurrence of elongate bacillary or "bayonet" forms within the erythrocyte is considered as characteristic of this genus.

The organism is transmitted by various tick species including Rhipicephalus, Dermacentor and Haemaphysalis. The organism reproduces in the tick as it progresses through its life stages.[8]

Both T annulata and T parva induce transformation of infected cells of lymphocyte or macrophage/monocyte lineages. T orientalis does not induce uncontrolled proliferation of infected leukocytes and instead multiplies predominantly within infected erythrocytes.


The genome of T orientalis has been sequenced.[9]


The genus is thought to have first appeared in ruminants during the Miocene.


Theileria can be transmitted to cattle through tick bites, including the brown ear tick Rhipicephalus spp.

Important species

Theileria parva

The cause of bovine Theileriosis and East Coast fever.[8]

Theileria annulata

Also the cause of bovine Theileriosis.[8]

Theileria equi

Causing equine piroplasmosis.[8]


External links

  • sequencing project
  • sequencing project
  • Tropical theileriosis - Wellcome Trust project
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