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Scientific classification
Domain: Eukaryota
(unranked): SAR
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[edit]

Theileria parva[edit]

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

Theileria annulata[edit]

Also the cause of bovine Theileriosis.[8]

Theileria equi[edit]

Causing equine piroplasmosis.[8]


  • Buparvaquone is a promising compound for the therapy and prophylaxis of all forms of theileriosis.


  1. ^ a b Morrison W, McKeever D (2006). "Current status of vaccine development against Theileria parasites". Parasitology 133: S169–87. doi:10.1017/S0031182006001867. PMID 17274845. 
  2. ^ Florin-Christensen, M.; Schnittger, L. (Jan 2009). "Piroplasmids and ticks: a long-lasting intimate relationship". Frontiers in Bioscience 14 (14): 3064–3073. doi:10.2741/3435. ISSN 1093-9946. PMID 19273257. 
  3. ^ Pain A, et al. (2005). "Genome of the host-cell transforming parasite Theileria annulata compared with T. parva.". Science 309 (5731): 131–3. doi:10.1126/science.1110418. PMID 15994557. 
  4. ^ Gardner MJ, et al. (2005). "Genome sequence of Theileria parva, a bovine pathogen that transforms lymphocytes". Science 309 (5731): 134–7. doi:10.1126/science.1110439. PMID 15994558. 
  5. ^ Englund, L. P. (2003). "New diseases and increased risk of diseases in companion animals and horses due to transport". Acta veterinaria Scandinavica. Supplementum 100: 19–25. ISSN 0065-1699. PMID 16429803. 
  6. ^ Darghouth, A. (Dec 2008). "Review on the experience with live attenuated vaccines against tropical theileriosis in Tunisia: considerations for the present and implications for the future". Vaccine. 26. Suppl 6: G4–G10. doi:10.1016/j.vaccine.2008.09.065. ISSN 0264-410X. PMID 19178892. 
  7. ^ "Cattle disease vaccine launched 30 years after invention". 2010-05-07. (7 May 2010).
  8. ^ a b c d *Theileria reviewed and published by WikiVet, accessed 11 October 2011.
  9. ^ Hayashida K, Hara Y, Abe T, Yamasaki C, Toyoda A, Kosuge T, Suzuki Y, Sato Y, Kawashima S, Katayama T, Wakaguri H, Inoue N, Homma K, Tada-Umezaki M, Yagi Y, Fujii Y, Habara T, Kanehisa M, Watanabe H, Ito K, Gojobori T, Sugawara H, Imanishi T, Weir W, Gardner M, Pain A, Shiels B, Hattori M, Nene V, Sugimoto C (2012) Comparative genome analysis of three eukaryotic parasites with differing abilities to transform leukocytes reveals key mediators of theileria-induced leukocyte transformation. MBio 3(5). pii: e00204-12. doi: 10.1128/mBio.00204-12

External links[edit]