Theileria

Theileria is a genus of parasites 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 species are transmitted by ticks.[2] The genomes of T. orientalis Shintoku[3], Theileria equi WA,[4] Theileria annulata Ankara[5] and Theileria parva Muguga[6] have been sequenced and published.

Theileria
Kinete stage of Theileria parva in the transmitting tick Rhipicephalus appendiculatus
Scientific classification
(unranked): Diaphoretickes
Clade: TSAR
Clade: SAR
Infrakingdom: Alveolata
Phylum: Apicomplexa
Class: Aconoidasida
Order: Piroplasmida
Family: Theileriidae
Genus: Theileria
Species

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

Theileria equi is a known cause of equine piroplasmosis.[7]

Vaccines against Theileria are in development.[1][8] In May 2010, a vaccine that was reported to protect cattle against East Coast fever had been approved and registered by the governments of Kenya, Malawi, and Tanzania.[9]

Description

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 elongated 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.[10] 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.

Genomics

The genomes of T. orientalis Shintoku[3], Theileria equi WA,[4] Theileria annulata Ankara[5] and Theileria parva Muguga[6] have been sequenced. Genomic data can be accessed PiroplasmaDB which is part of the Eukaryotic Pathogen Bioinformatic Resource (EuPathDB).[11]

Evolution

The genus is thought to have first appeared in ruminants during the Miocene. It is named for Gertrud Theiler, daughter of Arnold Theiler.

Transmission

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

Important species

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

References
  1. 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. 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): e00204–12. doi:10.1128/mBio.00204-12. PMC 3445966. PMID 22951932.
  4. Kappmeyer, Lowell S.; Thiagarajan, Mathangi; Herndon, David R.; Ramsay, Joshua D.; Caler, Elisabet; Djikeng, Appolinaire; Gillespie, Joseph J.; Lau, Audrey OT; Roalson, Eric H. (2012-01-01). "Comparative genomic analysis and phylogenetic position of Theileria equi". BMC Genomics. 13: 603. doi:10.1186/1471-2164-13-603. PMC 3505731. PMID 23137308.
  5. Pain, Arnab; Renauld, Hubert; Berriman, Matthew; Murphy, Lee; Yeats, Corin A.; Weir, William; Kerhornou, Arnaud; Aslett, Martin; Bishop, Richard (2005-07-01). "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.
  6. Gardner, Malcolm J.; Bishop, Richard; Shah, Trushar; de Villiers, Etienne P.; Carlton, Jane M.; Hall, Neil; Ren, Qinghu; Paulsen, Ian T.; Pain, Arnab (2005-07-01). "Genome sequence of Theileria parva, a bovine pathogen that transforms lymphocytes". Science. 309 (5731): 134–7. doi:10.1126/science.1110439. PMID 15994558.
  7. 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.
  8. 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.
  9. "Cattle disease vaccine launched 30 years after invention". 2010-05-07. SciDev.net (7 May 2010).
  11. Harb, Omar S.; Roos, David S. (2015-01-01). The Eukaryotic Pathogen Databases: a functional genomic resource integrating data from human and veterinary parasites. Methods in Molecular Biology. 1201. pp. 1–18. doi:10.1007/978-1-4939-1438-8_1. ISBN 978-1-4939-1437-1. PMC 6157018. PMID 25388105.
  12. Mehlhorn, Heinz; Schein, Eberhard (1998). "Redescription of Babesia equi Laveran, 1901 as Theileria equi Mehlhorn, Schein 1998". Parasitology Research. 84: 467–475. Retrieved June 19, 2020.
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