Theileria is a genus of parasites that belongs to thephylumApicomplexa, and is closely related toPlasmodium. TwoTheileria species,T. annulata andT. parva, are important cattle parasites.[1]T. annulata causestropical theileriosis andT. parva causesEast Coast fever.Theileria species are transmitted by ticks.[2]Thegenomes ofT. orientalis Shintoku[3], Theileria equi WA,[4]Theileria annulata Ankara[5] andTheileria parva Muguga[6] have been sequenced and published.
Vaccines againstTheileria 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]
Species in this genus undergo exoerythrocyticmerogony in thelymphocytes,histiocytes,erythroblasts, and other cells of the internal organs. This is followed by invasion of the erythrocytes by themerozoites, 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, includingRhipicephalus,Dermacentor, andHaemaphysalis. The organism reproduces in the tick as it progresses through its life stages.[10] BothT. annulata andT. parva induce transformation of infected cells oflymphocyte ormacrophage/monocyte lineages.T. orientalis does not induce uncontrolled proliferation of infected leukocytes and instead multiplies predominantly within infected erythrocytes.
The genomes ofT. orientalis Shintoku[3], Theileria equi WA,[4]Theileria annulata Ankara[5] andTheileria parva Muguga[6] have been sequenced. Genomic data can be accessed thoughPiroplasmaDB which is part of theEukaryotic Pathogen Database).[11]
^abPain, 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.PMID15994557.S2CID34556923.
^abGardner, 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.PMID15994558.S2CID37769438.
^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.ISSN0065-1699.PMID16429803.
^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.ISSN0264-410X.PMID19178892.
^Harb, Omar S.; Roos, David S. (2015-01-01). "The Eukaryotic Pathogen Databases: A Functional Genomic Resource Integrating Data from Human and Veterinary Parasites".Parasite Genomics Protocols. Methods in Molecular Biology. Vol. 1201. pp. 1–18.doi:10.1007/978-1-4939-1438-8_1.ISBN978-1-4939-1437-1.PMC6157018.PMID25388105.
