Trypanosoma vivax
| Trypanosoma vivax | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Trypanosoma vivax | ||||||||||||
| Ziemann , 1905 |
Trypanosoma vivax is a type of unicellular parasite within the genus of the trypanosomes , which occurs as a pathogen of the Nagana , an animal disease in ruminants , in Africa and in South America. The parasite is mostlytransmittedby tsetse flies ; it can reproduce in mammals as well as in tsetse flies. However, mechanical transmission through other blood-sucking insects in which no reproduction takes place is also important. In South America, the parasite is only transmitted mechanically without reproducing in the insect.
Discovery and Description
Trypanosoma vivax was described in 1905 by the German marine doctor Hans Ziemann (1865-1939), who was active as a medical consultant in Cameroon . The species was called vivax because the parasites move quickly in fresh blood drops under the microscope.
The protozoa has a single flagellum in all cell forms , which runs on the cell surface under an undulating membrane to the front end of the cell and there becomes a free-swinging flagellum. The cells also have a large kinetoplast, a collection of deoxyribonucleic acid within a large mitochondrion . The parasite occurs in mammals in a trypomastigote cell shape up to 26 µm long with a pear-shaped rear end. Besides trypomastigotes, epimastigotes are also observed in insects; these differ in the position of the flagellum base relative to the beginning of the cell.
Within the genus Trypanosoma , Trypanosoma vivax is classified in the subgenus Duttonella . In addition to the species, a subspecies is recognized; Trypanosoma vivax viennei occurs in South America and is microscopically indistinguishable from Trypanosoma vivax . The subspecies cannot reproduce in tsetse flies; the molecular cause for this is not known.
Distribution and host animals
Trypanosoma vivax occurs in sub-Saharan Africa in the distribution area of the tsetse fly, but also in neighboring countries outside the tsetse area, as well as on Mauritius, some Caribbean islands and South America. The species is the main pathogen of the Nagana in West Africa; in East Africa, other parasite species dominate, especially Trypanosoma congolense . In Africa the tsetse fly is by far the most important vector; outside the tsetse area, horseflies and calf sticks are likely carriers.
The import to South America was probably carried out by infected cattle from West Africa; the first reliable evidence in French Guiana dates from 1919, the date of import is probably in the 19th century. There are no tsetse flies in South America that could serve as a vector. A transmission through brakes and calf sticks has been proven experimentally; medical instruments or mother-to-calf transmission may also play a role. A vector in which the parasite can multiply could not be identified in South America.
Infections by Trypanosoma vivax mainly affect cattle, sheep and goats; Trypanosoma vivax is not known to affect humans . In addition to domestic animals, wild animals, including horses and antelopes, are considered reservoir hosts . In South America the capybara and the white-tailed deer can be infected, but the epidemiological significance as a reservoir is unclear.
Life cycle
Trypanosoma vivax has a complex life cycle with host changes between mammals and insects. In mammals, the trypomastigote parasite reproduces mainly in the blood, but it is also regularly found in lymph nodes, sometimes in the heart tissue and in the central nervous system. Tsetse flies ingest procyclic trypomastigote parasites during a blood meal on an infected mammal; they attach themselves to the inner wall of the proboscis of the insect. There the trypomastigote cells transform into epimastigote forms that can multiply. Then metacyclic trypomastigote cells form again from the epimastigote cells, which in turn can infect a mammal. Propagation in the proboscis is a specialty of the subgenus Duttonella . The relatively simple reproduction in insects is considered to be the cause of a high infection rate in tsetse flies. Like Trypanosoma brucei , Trypanosoma vivax shows antigen variability through frequent exchange of variable surface glycoproteins on the cell surface.
Individual evidence
- ↑ Steverding D. The history of African trypanosomiasis. In: Parasite Vectors. 2008 Feb 12; 1 (1): 3. PMID 18275594
- ^ Jones TW, Dávila AM. Trypanosoma vivax - out of Africa. In: Trends Parasitol. 2001 Feb; 17 (2): 99-101. PMID 11228017
- ↑ a b Osório AL, Madruga CR, Desquesnes M, Soares CO, Ribeiro LR, Costa SC. Trypanosoma (Duttonella) vivax: its biology, epidemiology, pathogenesis, and introduction in the New World - a review. In: Mem Inst Oswaldo Cruz. 2008 Feb; 103 (1): 1-13. PMID 18368231
literature
- Ian Maudlin, PH Holmes, Michael A. Miles (Eds.): The Trypanosomiases . Wallingford: CABI Publishing 2004 ISBN 085199475X
- Gardiner PR. Recent studies of the biology of Trypanosoma vivax. In: Adv Parasitol. 1989; 28: 229-317. PMID 2683616