''Trypanosoma vivax'' is a parasite species in the genus ''

Trypanosoma ''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Euglenozoa. The name is derived from the Ancient Greek ''trypano-'' (b ...

''. It causes the disease

nagana Animal trypanosomiasis, also known as nagana and nagana pest, or sleeping sickness, is a disease of non-human vertebrates. The disease is caused by trypanosomes of several species in the genus ''Trypanosoma'' such as '' T. brucei'' (which also ...

, affecting cattle or wild mammals. It is mainly occurs in

West Africa West Africa, also known as Western Africa, is the westernmost region of Africa. The United Nations geoscheme for Africa#Western Africa, United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Gha ...

, although it has spread to

South America 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 ...

Range

Historically restricted to

sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...

especially West Africa, it has spread to 13 countries of South America. This has been made easier by its mechanical transmission route, see below.

Hosts

Host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

s include,

cattle Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are calle ...

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 ...

sheep Sheep (: sheep) or domestic sheep (''Ovis aries'') are a domesticated, ruminant mammal typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to d ...

, and

camel A camel (from and () from Ancient Semitic: ''gāmāl'') is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provid ...

s. in South America it is an emerging pathogen of cattle, and sometimes horses and other

ruminant Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microb ...

s. The

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 ...

host is '' Glossina''.

Life cycle

Unusual for a trypanosome, ''T. vivax'' does not infect the '' Glossina'' vector

midgut The midgut is the portion of the human embryo from which almost all of the small intestine and approximately half of the large intestine develop. After it bends around the superior mesenteric artery, it is called the "midgut loop". It comprises ...

. Instead it infects and completes an abbreviated life cycle only in the vector's

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

. Thus it is entirely mechanically transmitted. For this reason it has had a relatively easy time jumping vectors, and thereby even jumping geographic ranges which do not have its customary vector.

Symptoms

Symptoms of ''T. vivax'' include "rapid weight loss, lethargy, weakness, clumsiness, pale mucosa, swelling of superficial lymph nodes, anemia, and fluctuating

pyrexia Fever or pyrexia in humans is a symptom of an anti-infection defense mechanism that appears with body temperature exceeding the normal range caused by an increase in the body's temperature set point in the hypothalamus. There is no single agre ...

, causing .. drop in animal productivity."

Enzymes

A novel proline racemase of medical and veterinary importance has been described in ''T. vivax'' (). It also produces vivapain, a

cysteine peptidase Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile. Cysteine is ...

Host immunity

The smallest

variable surface glycoprotein Variant surface glycoprotein (VSG) is a ~60kDa protein which densely packs the cell surface of protozoan parasites belonging to the genus ''Trypanosoma''. This genus is notable for their cell surface proteins. They were first isolated from ''Trypa ...

(40 kDa in size) to date has been found in ''T. vivax'', which bears little carbohydrate.

Economic impact

''Trypanosoma vivax'' is a significant drag on Africa's cattle production every year, and increasingly is a concern in South America: One outbreak in 1995 in the

Pantanal The Pantanal () is a natural region encompassing the world's largest tropical wetland area, and the world's largest Flooded grasslands and savannas, flooded grasslands. It is located mostly within the Brazilian state of Mato Grosso do Sul, but i ...

in Brazil and Bolivia cost the industry over US$160 million.

Trypanocide resistance

Some resistance to trypanocides has been observed: Some African countries have isometamidium-resistant populations, with some of these also being resistant to

diminazene Diminazene (INN; also known as diminazen) is an anti-infective medication for animals that is sold under a variety of brand names. It is effective against certain protozoa such as ''Babesia'', ''Trypanosoma'', and '' Cytauxzoon''. The drug may al ...

. (This has been ascribed variously to cross-resistance or to two separate events of acquisition of separate resistance genetics. Isometamidium and diminazene are not thought to be in the same trypanocide class.) Resistance to both is widespread in both West and

East Africa East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...

. Diminazene resistance has been observed in South America. Mechanisms of resistance are not necessarily shared across the genus, and this is especially true for this, the most genetically divergent species.

References

External links

{{Taxonbar, from=Q2456810 Trypanosomatida Parasites of mammals Parasitic excavates Euglenozoa species Protists described in 1905