Trypanosoma cruzi
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Trypanosoma cruzi Trypomastigote in the blood |
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| Trypanosoma cruzi | ||||||||||||
| Chagas , 1909 |
Trypanosoma cruzi is a unicellular parasite that is ofgreat medical importancein Latin America as the causative agent of Chagas disease ( American trypanosomiasis ). In endemic areas, the parasite circulates between blood-sucking predatory bugs and a wide variety of mammal species, including domestic animals.
Discovery and Description
Trypanosoma cruzi was first described in 1909 by the Brazilian doctor Carlos Chagas and named after the doctor Oswaldo Cruz . The unicellular organism has a single flagellum and a large kinetoplast . The parasite comes in several forms, which differ morphologically:
- The trypomastigote (elongated, convoluted) shape with a flagellum base near the nucleus is on average 20 micrometers long, has a long flagellum and a pointed rear end.
- The amastigote shape is up to 4 micrometers long, the flagellum is almost invisible.
- The epimastigote shape is similar to the trypomastigote, but the flagellum base is in a different position.
The kinetoplast, which is characteristic of the species of Kinetoplastea , is a collection of DNA within a large mitochondrion .
Due to biochemical differences, a distinction is made between two subtypes of T. cruzi , the relatively homogeneous type I and type II, which was further subdivided into IIa-e after molecular genetic analyzes. The types that currently have no taxonomic rank differ not only in molecular terms, but also in their typical host species, among other things. The name Trypanosoma cruzi cruzi as a subspecies for all isolates pathogenic to humans is no longer in use. The subspecies Trypanosoma cruzi marinkellei was isolated from South American bats .
Distribution and host animals
Trypanosoma cruzi is common in South and Central America from Mexico to southern Argentina, particularly poor, rural areas are affected. Infected animals are also found in the USA.
Among the insects, predatory bugs of the subfamily Triatominae are intermediate hosts, especially species of the genera Rhodnius and Triatoma . The most important vector in human infection is Triatoma infestans . Among the mammals, domestic animals such as dogs and cats, but also rodents living close to the house, are important hosts, while among the wild animals opossums (for T. cruzi type I) and armadillos (for T. cruzi type II) are the most important reservoirs.
Life cycle
In the intestines of the predatory bugs, the parasite ingested during a blood meal changes from a trypomastigote to an epimastigote; these can multiply in the bug's digestive tract by dividing. In the rectum of the bedbugs, the epimastigotes turn into new trypomastigotes, which are excreted with the faeces and can infect mammalian hosts through skin injuries or mucous membranes.
In mammals, the parasites occur as trypomastigotes in the bloodstream or as amastigotes inside body cells. After infection, macrophages in the skin are usually the first target. The intracellular amastigotes can multiply in the cytoplasm of the host cell by division and, after being converted again into trypomastigotes, destroy the host cell. They get back into the bloodstream and can infect other body cells of the vertebrate host, including heart muscle cells, or a new blood-sucking predatory bug.
Trypomastigotes can also be transmitted from person to person through blood transfusions and organ transplants, as well as through the placenta from the mother to the fetus.
Molecular Properties
The complete genome - the DNA sequence of Trypanosoma cruzi was published in 2005; the 60 mega base pair genome is highly repetitive and contains around 12,000 different genes. The parasite has a glycocalyx on the cell surface with a complex range of surface antigens , including many glycoconjugates . Accordingly, trans-sialidases are particularly well represented in the genome, as are other gene families that are important for the cell surface, such as mucins and mucin-associated surface proteins ; all of these gene families are represented with several hundred genes each. They obviously play an important role in bypassing the mammalian host's immune system.
There are only two drugs that are used in medicines for Chagas disease, nifurtimox and benznidazole . Both work through the formation of free radicals during metabolism; the parasite is unable to break them down because it lacks the appropriate enzymes or has only low activity. Due to the genome sequence, however, there are now a number of new targets that can be used for the development of new drugs.
therapy
Infections with Trypanosoma cruzi that require treatment are treated with benznidazole or nifurtimox after consultation with a center experienced in therapy.
Individual evidence
- ↑ C. Chagas: New Trypanosomes. Preliminary communication. In: Archives for ship and tropical hyg. 13, 1909, pp. 120-122. online ( Memento from April 13, 2007 in the Internet Archive )
- ↑ C. Chagas: About a new trypanosomiasis in humans. In: Archives for ship and tropical hyg. 13, 1909, pp. 351-353. online ( Memento from April 12, 2007 in the Internet Archive )
- ^ S. Brisse, C. Barnabé, M. Tibayrenc: Identification of six Trypanosoma cruzi phylogenetic lineages by random amplified polymorphic DNA and multilocus enzyme electrophoresis. In: Int J Parasitol. 30 (1), Jan 2000, pp. 35-44. PMID 10675742
- ↑ dpd.cdc.gov Information from the American Centers for Disease Control (CDC) on Chagas disease
- ↑ M. Yeo, N. Acosta, M. Llewellyn, H. Sánchez, S. Adamson, GA Miles, E. López, N. González, JS Patterson, MW Gaunt, AR de Arias, MA Miles: Origins of Chagas disease: Didelphis species are natural hosts of Trypanosoma cruzi I and armadillos hosts of Trypanosoma cruzi II, including hybrids. In: Int J Parasitol. 35 (2), Feb 2005, pp. 225-233. PMID 15710443
- ↑ Emile Santos Barrias, Tecia Maria Ulisses de Carvalho, Wanderley De Souza: Trypanosoma cruzi: Entry into Mammalian Host Cells and Parasitophorous Vacuole Formation. In: Frontiers in Immunology. 4, 2013, p. 186. doi: 10.3389 / fimmu.2013.00186 . (Review)
- ↑ a b El-Sayed et al.: The genome sequence of Trypanosoma cruzi. etiological agent of Chagas disease. In: Science. 309 (5733), Jul 15, 2005, pp. 409-415. PMID 16020725
- ↑ Maya et al.: Mode of action of natural and synthetic drugs against Trypanosoma cruzi and their interaction with the mammalian host. In: Comp Biochem Physiol A Mol Integr Physiol . 146 (4), Apr 2007, pp. 601-620. PMID 16626984
- ^ Marianne Abele-Horn: Antimicrobial Therapy. Decision support for the treatment and prophylaxis of infectious diseases. With the collaboration of Werner Heinz, Hartwig Klinker, Johann Schurz and August Stich, 2nd, revised and expanded edition. Peter Wiehl, Marburg 2009, ISBN 978-3-927219-14-4 , p. 295.