Theileria
Encyclopedia
Theileria is a genus of parasitic protozoa
n that belongs to the phylum
Apicomplexa
and is closely related to Plasmodium
. Two Theileria species, T. annulata and T. parva, are important cattle parasites. T. annulata causes tropical theileriosis
and T. parva causes East Coast fever
. Theileria are transmitted by ticks.
The genomes of T. annulata and T. parva have been sequenced and published.
Theileria equi is a known cause of equine piroplasmosis.
Vaccines against Theileria are in development. 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.
s, histiocyte
s, 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.
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
n that belongs to the phylum
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
Apicomplexa
Apicomplexa
The Apicomplexa are a large group of protists, most of which possess a unique organelle called apicoplast and an apical complex structure involved in penetrating a host's cell. They are unicellular, spore-forming, and exclusively parasites of animals. Motile structures such as flagella or...
and is closely related to Plasmodium
Plasmodium
Plasmodium is a genus of parasitic protists. Infection by these organisms is known as malaria. The genus Plasmodium was described in 1885 by Ettore Marchiafava and Angelo Celli. Currently over 200 species of this genus are recognized and new species continue to be described.Of the over 200 known...
. Two Theileria species, T. annulata and T. parva, are important cattle parasites. T. annulata causes tropical theileriosis
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....
and T. parva causes East Coast fever
East Coast fever
-Introduction:East Coast fever is a disease of cattle, sheep and goats caused by the protozoan parasite Theileria parva. The term excludes diseases caused by other Theileria, such as tropical theileriosis , caused by T. annulata, and human theileriosis, caused by T...
. Theileria are transmitted by ticks.
The genomes of T. annulata and T. parva have been sequenced and published.
Theileria equi is a known cause of equine piroplasmosis.
Vaccines against Theileria are in development. 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.
Description
Species in this genus undergo exoerythrocytic merogony in the lymphocyteLymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
s, histiocyte
Histiocyte
A histiocyte is a cell that is part of the mononuclear phagocyte system . The mononuclear phagocytic system is part of the organism's immune system...
s, 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
Rhipicephalus
Rhipicephalus is a genus of tick.-Species:* Rhipicephalus annulatus Say, 1821* Rhipicephalus appendiculatus Neumann 1901* Rhipicephalus aquatilis Walker, Keirans & Pegram, 1993* Rhipicephalus armatus Pocock, 1900...
, Dermacentor
Dermacentor
Dermacentor is a genus of hard-bodied ticks.-Species:* Dermacentor abaensis Teng, 1963* Dermacentor albipictus Packard, 1869* Dermacentor andersoni Stiles 1908* Dermacentor asper Arthur, 1960...
and Haemaphysalis
Haemaphysalis
Haemaphysalis is a genus of tick.-Species:* Haemaphysalis aborensis Warburton, 1913* Haemaphysalis aciculifer Warburton 1913* Haemaphysalis aculeata Lavarra, 1904* Haemaphysalis adleri Feldman-Muhsam, 1951...
. The organism reproduces in the tick as it progresses through its life stages.