Trichinae
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Larva released from the capsule |
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| Trichinella | ||||||||||||
| Railliet , 1895 | ||||||||||||
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Trichinae ( Trichinella ) are a genus of tiny roundworms (strain Nematoda ) with a parasitic way of life. Mammals , including humans , and birds serve as intermediate and final hosts . The main vector for humans are pigs or their raw, z. B. Meat consumed as mince or insufficiently cooked meat. Trichinae are killed by cooking, curing or freezing, but not by smoking.
The clinical picture caused by trichinae is called trichinella , whereby humans are usually a false host , since they are not eaten by potential final hosts and thus do not contribute to the further reproduction of the trichinae. Acute infections in humans with Trichinella spiralis are notifiable in Germany . The trichinae test is a compulsory test of meat for human consumption. A quick analysis is possible using MALDI-TOF .
distribution
The trichinae are distributed worldwide by several species.
In western countries they occur predominantly in the " silvatic cycle " in which foxes and rodents spread the worms by eating infected animals. In more northerly areas, bears, sled dogs and seals can also serve as intermediate hosts. An “urban cycle” is also pronounced, in which the pathogens are mainly spread by rats and pigs.
features
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The adult animals reach a length of up to 4 mm (females) or 1.5 mm (males). One can clearly see the thickened rear end that houses the intestine. The larvae develop in the muscle tissue and form a "nurse cell nutrient complex" there, a capsule that is supplied with plenty of blood vessels and thus keeps the larva alive. It reaches a size of around one millimeter and is highly infectious. However, there are also variants that do not form a capsule, such as. B. Trichinella pseudospiralis .
Life cycle
In the case of trichinae, each host initially serves as an intermediate host , since the larvae first mature into worms in the intestine. Larvae encapsulated in the meat of infected animals are ingested when it is consumed. The capsules are dissolved in the small intestine and the larvae are released. The worms dig into the epithelium of the small intestine and develop into an adult animal within 30 hours, after which they mate. In the small intestine, the females give birth to up to 1500 larvae while giving birth. The larvae then drill through the small intestine and thus reach the lymph or the bloodstream . They drift through the body and mainly settle in the striated, well-perfused muscle tissue. The diaphragm , eyes and tongue are also affected . Where a larva settles, the formation of a nurse cell nutrient complex begins, which remains infectious as long as the parasite lives. From the fifth month onwards, calcification takes place in the human tissue, which causes nurse cells and larvae to die, although the encysted muscle trichinae will probably remain viable for another 5 to 10 years.
Effect on humans
Adult trichinae in the intestine usually lead to dizziness, abdominal pain, vomiting and diarrhea in humans. If the larvae then spread in the body, further symptoms such as weakness, fever and edema in the facial area occur as a result of myositis . These symptoms are temporary and can last up to a year. After that, they mostly disappear again and have no consequences. A fatal course occurs especially when the heart muscles are more severely affected (parasitic myocarditis ).
Word origin
Made from hair by the Greek trichonos .
See also
Web links
Individual evidence
- ^ Anne Mayer-Scholl, J. Murugaiyan, J. Neumann, P. Bahn, S. Reckinger, Karsten Nöckler: Rapid identification of the foodborne pathogen Trichinella spp. by matrix-assisted laser desorption / ionization mass spectrometry. In: PLoS One. 11/2016, p. E0152062. doi: 10.1371 / journal.pone.0152062 .
- ↑ Ursus-Nikolaus Riede: Pocket Atlas of General Pathology: Pathological Principles - Associated Diseases - Subsequent Conditions . Thieme, Stuttgart a. a. 1998, ISBN 3-13-115451-9 .
- ↑ Trichina. In: True dictionary of origin. from: Wissen.de , accessed on May 22, 2014.
swell
- Occurrence of trichinella in wild boar in Germany and options for intervention. (PDF file; 201 kB). BfR report, July 6, 2007.
- J. Dönges: Parasitology. With special consideration of human pathogenic forms. Thieme, Stuttgart 1988, ISBN 3-13-579902-6 .
- H. Mehlhorn, G. Piekarski: Outline of parasite science. 6th edition. Heidelberg 2002, ISBN 3-8274-1158-0 .
- I. Remde: Investigations into the occurrence of the zoonotic pathogens Echinococcus multilocularis and Trichinella spp. with wild boar (Sus scrofa scrofa) in the Wartburg district. Dissertation . FU Berlin, 2008.