''Theileria'' is a genus of parasites that belongs to the
phylum Apicomplexa
The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. Th ...
, 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 vecto ...
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 ap ...
. ''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 tic ...
.
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
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 i ...
in the lymphocyte
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...
s, 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
''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
''Dermacentor'' is a genus of ticks in the family Ixodidae, the hard ticks. The genus has a cosmopolitan distribution, with native species on all continents except Australia. Most occur in the Nearctic realm.
Hosts of ''Dermacentor'' ticks inc ...
'', and'' Haemaphysalis
''Haemaphysalis'' is a genus of ticks, containing these species:
*'' Haemaphysalis aborensis'' Warburton, 1913
*'' Haemaphysalis aciculifer'' Warburton, 1913
*'' Haemaphysalis aculeata'' Lavarra, 1904
*'' Haemaphysalis adleri'' Feldman-Muhsam, 1 ...
''. The organism reproduces in the tick as it progresses through its life stages.[Theileria]
reviewed and published by WikiVet
WikiVet is a wiki of veterinary content based on the MediaWiki platform. The website is a collaborative initiative between various veterinary schools, and its content covers the entire veterinary curriculum. WikiVet is part of the WikiVet Educatio ...
, accessed 11 October 2011. Both ''T. annulata'' and ''T. parva'' induce transformation of infected cells of lymphocyte
A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic adap ...
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'', 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).
Evolution
The genus is thought to have first appeared in ruminants during the Miocene. It is named for Gertrud Theiler, 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 ...
.
Transmission
''Theileria'' spp. can be transmitted to cattle through tick bites, including the brown ear tick, a ''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 ...
'' sp.
Important species
*''T. parva'' is the cause of bovine theileriosis and 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 ap ...
.
*''T. annulata'' also is a cause of bovine theileriosis.
*''T. equi'' causes 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 tic ...
. 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. Buparvaquone has been shown to have anti-leishmanial activity ''in vitro''. It can ...
is a promising compound for the therapy and prophylaxis of all forms of theileriosis.
References
External links
''Theileria annulata'' sequencing project
''Theileria parva'' sequencing project
PiroplasmaDB
— 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 ''Bab ...
{{Taxonbar, from=Q5233857
Piroplasmida
Apicomplexa genera