''Theileria'' is a genus of parasites that belongs to the

phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...

Apicomplexa, and is closely related to '' Plasmodium''. Two ''Theileria'' species, ''T. annulata'' and ''T. parva'', are important cattle parasites. ''T. annulata'' causes

tropical theileriosis Tropical theileriosis or Mediterranean theileriosis is a theileriosis of cattle from the Mediterranean and Middle East area, from Morocco to Western parts of India and China. It is a tick-borne disease, caused by ''Theileria annulata''. The vect ...

and ''T. parva'' causes

East Coast fever East Coast fever, also known as theileriosis, is a disease of cattle which occurs in Africa and is caused by the protozoan parasite ''Theileria parva''. The primary vector which spreads ''T. parva'' between cattle is a tick, ''Rhipicephalus appe ...

. ''Theileria'' species are transmitted by ticks. The genomes of ''T. orientalis'' Shintoku'', Theileria equi'' WA, ''Theileria annulata'' Ankara and ''Theileria parva'' Muguga have been sequenced and published. ''Theileria equi'' is a known cause of

equine piroplasmosis Babesiosis or piroplasmosis is a malaria-like parasitic disease caused by infection with a eukaryotic parasite in the order Piroplasmida, typically a ''Babesia'' or ''Theileria'', in the phylum Apicomplexa. Human babesiosis transmission via ti ...

. Vaccines against ''Theileria'' are in development. 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.

Description

Species in this genus undergo exoerythrocytic merogony in the lymphocytes, histiocytes,

erythroblast A nucleated red blood cell (NRBC), also known by several other names, is a red blood cell that contains a cell nucleus. Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of the ...

s, and other cells of the internal organs. This is followed by invasion of the erythrocytes by the

merozoite Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism is ...

s, 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 ''Rhipicephalus'' is a genus of ticks in the family Ixodidae, the hard ticks, consisting of about 74 or 75 species. Most are native to tropical Africa.Olwoch, J. M., et al. (2007)Climate change and the genus ''Rhipicephalus'' (Acari: Ixodidae) in ...

, Dermacentor'', and'' Haemaphysalis''. The organism reproduces in the tick as it progresses through its life stages.Theileria
reviewed and published by WikiVet, accessed 11 October 2011. Both ''T. annulata'' and ''T. parva'' induce transformation of infected cells of lymphocyte or

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

/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'', Theileria equi'' WA, ''Theileria annulata'' Ankara and ''Theileria parva'' Muguga have been sequenced. Genomic data can be accesse
PiroplasmaDB
which is part of the Eukaryotic Pathogen Bioinformatic Resource (

EuPathDB The Eukaryotic Pathgen Database, or EuPathDB, is a database of bioinformatic and experimental data related to a variety of eukaryotic pathogens. It was established in 2006 under a National Institutes of Health program to create Bioinformatics Reso ...

Evolution

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

Gertrud Theiler Gertrud Theiler (11 September 1897 – 2 May 1986) was a South African parasitologist and teacher most noted for her work with nematodes and ticks. Early life Born on 11 September 1897 in Pretoria, South Africa, Theiler graduated from Pretori ...

, daughter of

Arnold Theiler Sir Arnold Theiler KCMG (26 March 1867 – 24 July 1936) Pour le Mérite is considered to be the father of veterinary science in South Africa. He was born in Frick, Canton Aargau, Switzerland. He received his higher education, and later qu ...

Transmission

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

'' sp.

Important species

*''T. parva'' is the cause of bovine theileriosis and

. *''T. annulata'' also is a cause of bovine theileriosis. *''T. equi'' causes

. It was originally classified as ''Babesia equi'' in 1901 by

Charles Louis Alphonse Laveran Charles Louis Alphonse Laveran (18 June 1845 – 18 May 1922) was a French physician who won the Nobel Prize in Physiology or Medicine in 1907 for his discoveries of parasitic protozoans as causative agents of infectious diseases such as malaria ...

, but was reclassified as ''T. equi'' in 1998 by Heinz Mehlhorn and Eberhard Schein.

Treatment

Buparvaquone Buparvaquone is a naphthoquinone antiprotozoal drug related to atovaquone. It is a promising compound for the therapy and prophylaxis of all forms of theileriosis (disambiguation), theileriosis. Buparvaquone has been shown to have anti-leishmanial ...

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

References

External links

''Theileria annulata'' sequencing project''Theileria parva'' sequencing projectPiroplasmaDB
— genomic and functional genomic resource for

piroplasmida Piroplasmida is an order of parasites in the phylum Apicomplexa. They divide by binary fission and as sporozoan parasites they possess sexual and asexual phases (sexual reproduction occurs in the tick gut). They include the tick parasites ''Ba ...

{{Taxonbar, from=Q5233857 Piroplasmida Apicomplexa genera