''Trypanosoma'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of kinetoplastids (class Trypanosomatidae), a

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group of unicellular parasitic

flagellate A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and the ...

protozoa Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...

. Trypanosoma is part of the phylum Euglenozoa. The name is derived from the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''trypano-'' (borer) and ''soma'' (body) because of their corkscrew-like motion. Most trypanosomes are

heteroxenous Heteroxeny, or heteroxenous development, characterizes a parasite whose development involves several host species. Heteroxeny has been used as the basis for splitting genera. When there are two or three hosts, the development cycle is named d ...

(requiring more than one obligatory host to complete life cycle) and most are transmitted via a

vector Vector most often refers to: * Euclidean vector, a quantity with a magnitude and a direction * Disease vector, an agent that carries and transmits an infectious pathogen into another living organism Vector may also refer to: Mathematics a ...

. The majority of species are transmitted by blood-feeding

invertebrates Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...

, but there are different mechanisms among the varying species. '' Trypanosoma equiperdum'' is spread between horses and other equine species by sexual contact. They are generally found in the intestine of their invertebrate host, but normally occupy the bloodstream or an

intracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

environment in the vertebrate host. Trypanosomes infect a variety of hosts and cause various diseases, including the fatal human diseases

sleeping sickness African trypanosomiasis is an insect-borne parasitic infection of humans and other animals. Human African trypanosomiasis (HAT), also known as African sleeping sickness or simply sleeping sickness, is caused by the species '' Trypanosoma b ...

, caused by '' Trypanosoma brucei'', and Chagas disease, caused by '' Trypanosoma cruzi.'' The mitochondrial genome of the ''Trypanosoma'', as well as of other kinetoplastids, known as the

kinetoplast A kinetoplast is a network of circular DNA (called kDNA) inside a mitochondrion that contains many copies of the mitochondrial genome. The most common kinetoplast structure is a disk, but they have been observed in other arrangements. Kinetoplasts ...

, is made up of a highly complex series of catenated circles and minicircles and requires a cohort of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s for organisation during

cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...

History

In 1841, Gabriel Valentin found flagellates that today are included in '' Trypanoplasma'' in the blood of trout. The genus (''T. sanguinis'') was named by Gruby in 1843, after parasites in the blood of frogs. In 1903, David Bruce identified the protozoan parasite and the

tsetse fly Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies) are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Gloss ...

vector of

African trypanosomiasis African trypanosomiasis is an insect-borne parasitic infection of humans and other animals. Human African trypanosomiasis (HAT), also known as African sleeping sickness or simply sleeping sickness, is caused by the species ''Trypanosoma bru ...

Taxonomy

A number of different methods demonstrate that the traditional ''Trypanosoma'' genus is not monophyletic, with the biflagellate Bodonida nested within. The American and African trypanosomes constitute distinct clades, implying that the major human disease agents ''T. cruzi'' (cause of Chagas' disease) and ''T. brucei'' (cause of African sleeping sickness) are not closely related to each other. Phylogenetic analyses suggest an ancient split between a branch containing all Salivarian trypanosomes and a branch containing all non-Salivarian lineages. The latter branch in turn splits into a clade containing bird, reptilian and the Stercorarian trypanosomes infecting mammals, and a clade with a branch of fish trypanosomes and a branch of reptilian or amphibian lineages. Salivarians are trypanosomes of the subgenera of '' Duttonella'', '' Trypanozoon'', '' Pycnomonas'' and '' Nannomonas'', which are passed to the vertebrate recipient in the saliva of the tsetse fly (''Glossina spp.''). Antigenic variation is a characteristic shared by the Salivaria, which has been particularly well-studied in '' T. brucei''. The '' Trypanozoon'' subgenus contains the species '' Trypanosoma brucei'', '' T. rhodesiense'' and '' T. equiperdum''. The subgenus '' Duttonella'' contains the species '' T. vivax''. '' Nannomonas'' contains '' T. congolense''.Dihydrofolate reductases within the genus Trypanosoma. J.J. Jaffe, J.J. McCormack Jr and W.E. Gutteridge, Experimental Parasitology, 1969, Volume 25, Pages 311–318, Stercorians are trypanosomes passed to the recipient in the feces of insects from the subfamily '' Triatominae'' (most importantly '' Triatoma infestans''). This group includes '' Trypanosoma cruzi'', '' T. lewisi'', '' T. melophagium'', '' T. nabiasi'', '' T. rangeli'', '' T. theileri'', '' T. theodori''. The subgenus '' Herpetosoma'' contains the species '' T. lewisi''. The subgenus '' Schizotrypanum'' contains '' T. cruzi'' and a number of bat trypanosomes. The bat species include '' Trypanosoma cruzi marinkellei'', '' Trypanosoma dionisii'', '' Trypanosoma erneyi'', '' Trypanosoma livingstonei'' and ''

Trypanosoma wauwau ''Trypanosoma'' is a genus of Kinetoplastida, kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasite, parasitic flagellate protozoa. Trypanosoma is part of the phylum Euglenozoa. The name is derived from the Ancien ...

''. Other related species include '' Trypanosoma conorhini'' and '' Trypanosoma rangeli''.

Evolution

The ancestor of modern trypanosomes absorbed a

green alga The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( ...

around one billion years ago and co-opted some of its genetic material. This has resulted in modern trypanosomes such as ''T. brucei'' containing essential genes for the breakdown of sugars that are most closely related to plants. This difference may be used as the target of therapies. The relationships between the species have not been worked out to date. It has been suggested that ''T. evansi'' arose from a clone of ''T. equiperdum'' which lost its maxicircles.Brun R, Hecker H, Lun ZR (1998) ''Trypanosoma evansi'' and ''T. equiperdum'': distribution, biology, treatment and phylogenetic relationship (a review). Vet Parasitol 79(2):95-107 It has also been proposed that ''T. evansi'' should be classified as a subspecies of ''T. brucei''.Carnes J, Anupama A, Balmer O, Jackson A, Lewis M, Brown R, Cestari I, Desquesnes M, Gendrin C, Hertz-Fowler C, Imamura H, Ivens A, Kořený L, Lai DH, MacLeod A, McDermott SM, Merritt C, Monnerat S, Moon W, Myler P, Phan I, Ramasamy G, Sivam D, Lun ZR, Lukeš J, Stuart K, Schnaufer A (2015) Genome and phylogenetic analyses of ''Trypanosoma evansi'' reveal extensive similarity to ''T. brucei'' and multiple independent origins for dyskinetoplasty. PLoS Negl Trop Dis 9(1):e3404. doi: 10.1371/journal.pntd.0003404 It has been shown that ''T. equiperdum'' has emerged at least once in Eastern Africa and ''T. evansi'' at two independent occasions in Western Africa.Cuypers B, Van den Broeck F, Van Reet N, Meehan CJ, Cauchard J, Wilkes JM, Claes F, Goddeeris B, Birhanu H, Dujardin JC, Laukens K, Büscher P, Deborggraeve S (2017) Genome-wide SNP analysis reveals distinct origins of ''Trypanosoma evansi'' and ''Trypanosoma equiperdum''. Genome Biol Evol doi: 10.1093/gbe/evx102

Selected species

Species of ''Trypanosoma'' include the following: * '' T. ambystomae''. in

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

s * '' T. antiquus'', extinct (Fossil in Miocene amber) * '' T. avium'', which infects birds and blackflies * '' T. bennetti'', which infects birds and biting midges * '' T. boissoni'', in elasmobranch * '' T. brucei'', which causes

in humans and nagana in cattle * '' T. cruzi'', which causes Chagas disease in humans * '' Trypanosoma culicavium'', which infects birds and mosquitoes * '' T. congolense'', which causes nagana in ruminant livestock, horses and a wide range of wildlife * '' T. equinum'', in

South American South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

horses, transmitted via Tabanidae, * '' T. equiperdum'', which causes dourine or covering sickness in

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

s and other

Equidae Equidae (commonly known as the horse family) is the Taxonomy (biology), taxonomic Family (biology), family of Wild horse, horses and related animals, including Asinus, asses, zebra, zebras, and many extinct species known only from fossils. The fa ...

, it can be spread through coitus. * '' T. evansi'', which causes one form of the disease surra in certain animals including camels Article Number 21. p.2 (a single case report of human infection in 2005 in India was successfully treated with suramin) * '' T. everetti'', in birds * '' T. hosei'', in

s * '' T. irwini'', in

koala The koala (''Phascolarctos cinereus''), sometimes inaccurately called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only Extant taxon, extant representative of the Family (biology), family ''Phascolar ...

s * '' T. lewisi'', in rats * '' T. melophagium'', in sheep, transmitted via '' Melophagus ovinus'' * '' T. parroti'', in amphibians * '' T. percae'', in the species '' Perca fluviatilis'' * '' T. phedinae'' * '' T. rangeli'', believed to be nonpathogenic to humans * '' T. rotatorium'', in amphibians * '' T. rugosae'', in amphibians * '' T. sergenti'', in amphibians * '' T. simiae'', which causes nagana in pigs. Its main reservoirs are warthogs and bush pigs * '' T. sinipercae'', in fishes * '' T. suis'', which causes a different form of surra * '' T. theileri'', a large trypanosome infecting ruminants and transmitted by a variety of vectors including tabanids and mosquitoes * '' T. thomasbancrofti'', an avian trypanosome with culicine mosquito vector * '' T. triglae'', in marine

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

s * '' T. tungarae'', in frogs * '' T. vivax'', which causes the disease nagana, mainly in West Africa, although it has spread to South America

Hosts, life cycle and morphologies

Two different types of trypanosomes exist, and their life cycles are different, the salivarian species and the stercorarian species. Stercorarian trypanosomes infect insects, most often the triatomid kissing bug, by developing in the posterior gut followed by release into the feces and subsequent depositing on the skin of the vertebrate host. The organism then penetrates and can disseminate throughout the body. Insects become infected when taking a blood meal. Salivarian trypanosomes develop in the anterior gut of insects, most importantly the

Tsetse fly Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies) are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Gloss ...

, and infective organisms are inoculated into the host by the insect bite before it feeds. As trypanosomes progress through their life cycle they undergo a series of morphological changes as is typical of trypanosomatids. The life cycle often consists of the trypomastigote form in the vertebrate host and the trypomastigote or promastigote form in the gut of the invertebrate host. Intracellular lifecycle stages are normally found in the amastigote form. The trypomastigote morphology is unique to species in the genus ''Trypanosoma''.

Meiosis

Evidence has been obtained for meiosis in '' T. cruzi'', and for genetic exchange. '' T. brucei'' is able to undergo

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

within the

salivary gland The salivary glands in many vertebrates including mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands ( parotid, submandibular, and sublingual), as well as hundreds of min ...

s of its

host, and meiosis is considered to be an intrinsic part of the ''T. brucei'' developmental cycle. An adaptive benefit of meiosis for ''T. crucei'' and ''T. brucei'' may be the recombinational repair of DNA damages that are acquired in the hostile environment of their respective hosts.Bernstein H, Bernstein C, Michod RE (2018). Sex in microbial pathogens. ''Infection, Genetics and Evolution'' volume 57, pages 8-25. https://doi.org/10.1016/j.meegid.2017.10.024

References

External links

Trypanosoma
reviewed and published by Wikivet, accessed 08/10/2011.
Trykipedia
Trypanosomatid specific ontologies
Tree of Life: Trypanosoma
{{Authority control Trypanosomatida Fish diseases Euglenozoa genera pl:Świdrowce