Filaria

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Filaria
Wuchereria bancrofti

Wuchereria bancrofti

Systematics
without rank: Bilateria
Over trunk : Molting animals (Ecdysozoa)
Trunk : Roundworms (Nematoda)
Class : Secernentea
Order : Spirurida (Spirurida)
Superfamily : Filaria
Scientific name
Filarioidea
Wine Country , 1858
Familys

The filaria (Filarioidea, from Latin filum , "thread") are a superfamily of roundworms (nematodes), which includes the two families Filariidae and Onchocercidae . The species are endoparasitic and some species of these groups are important as causative agents of parasitoses in humans or in domestic animals, the so-called filariasis .

features

Filaria are slender and thread-like worms whose body length varies between 2 and 50 centimeters, depending on the species. They have a rounded front end with no pronounced lips. The larval stages of the filariae, known as microfilariae, are smaller than a millimeter.

Way of life

The filariae live mainly in the blood and lymph vessels of vertebrates and in crevices of connective tissue .

Life cycle

The filariae are for the most part viviparous and deposit their larvae, the microfilariae, or embryonated eggs directly into the vessels or tissue in which they reside. They appear in the skin or in the blood, from where they are ingested by blood-sucking insects such as mosquitoes or horseflies , which act as intermediate hosts and vectors . In these they develop from the first larval stage to the infectious larva over two moults. The infectious larvae return to a definitive host (including humans) when stung and migrate to their final location. The insects ingest the larvae of the filariae, the microfilariae, with the blood of their host and at the same time release the developed filariae into the blood and lymphatic system. Here, after two further moults, they become what is known as an adult filament.

Black fly with Onchocerca filament emerging on the left antennae

Mosquitoes play a central role in the transmission of the pathogen causing lymphatic filariasis. Thus Mangifera by mosquitoes of the genus Aedes and Culex transmit Brugia malayi of species of the genus Anopheles and Mansonia . Vectors of the Loiasis are brakes of the genus Chrysops and Onchocercas volvulus is only of individual species of black flies of the genus Simulium transmitted. Blood-sucking mites or ticks can also play a role in filariae pathogenic to animals, for example in Litomosoides carinii , which infects rats.

Filariasis

Various diseases that go back to infection with filariasis are named as filariasis . Accordingly, they belong to the worm diseases. Filariasis manifests itself, depending on the species, primarily in the lymphatic system or in the superficial and deeper connective tissue. Filariasis are differentiated according to the different lifestyles of the filariae and the associated symptoms of the disease.

Lymphatic forms, triggered by species living in the lymphatic system, are regarded as filariasis in the strict sense of the word. They are mainly caused by the filariae Wuchereria bancrofti , Brugia malayi and Brugia timori .

  • Elephantiasis of the leg caused by microfilariae

  • Elephantiasis of the leg caused by microfilariae

  • Africans with genital elephantiasis, 1906

Another filariasis is the loiasis of the tropical rainforest areas of Africa, which is triggered by loa loa . In contrast to lymphatic filariasis, the filariae migrate in the subcutaneous tissue (wandering filariasis), in the connective tissue under the skin and below the conjunctiva of the eye (subconjunctival). If loa loa occurs in the eye, it is referred to as an "eye worm".

The Onchocerciasis , also known as knotenfilariose, is caused by infection with volvulus Onchocercas triggered. As with loiasis, the adult worms also live in the subcutaneous connective tissue in this infection. However, they do not migrate, but stay locally in nodes and release their larvae into the adjacent connective tissue. The larvae destroy the elastic fibers here and lead to chronic itching , skin inflammation ( dermatitis ), lichenification , atrophy of the affected tissue, depigmentation of the skin and detachment of skin folds in the connective tissue ( presbyteria ). In the epidemic areas, infestation of the eyes with microfilariae leads to blindness, known as river blindness, in up to 10% of cases of infection.

Pathogens in humans

  • Wuchereria bancrofti

  • Brugia malayi

  • Microfilariae of Loa loa (right) and Mansonella perstans (left) in the same blood smear

  • Onchocerca volvulus

Pathogens of farm animals / pets (selection)

supporting documents

  1. ^ MeSH Library of Medicine - Medical Subject Headings. Filarioidea filaria
  2. ↑ www.ncbi.nlm.nih.gov . Retrieved May 21, 2009.
  3. ↑ a b Gerhard Hartwich : Tribe Nemathelminthes or Aschelminthes - tubular worms. Urania Tierreich, Volume Invertebrates 1, Urania Verlag Berlin 2000; P. 353 ff. ISBN 3-332-01174-X
  4. ↑ a b c Keyword "Filariasis" in Pschyrembel Dictionary Sexuality. Walter de Gruyter, Berlin 2006; P. 473. ISBN 3-11-016965-7 .
  5. ^ Keyword "Filariasis" in Heinz Mehlhorn (Ed.): Encyclopedic Reference of Parasitology. Biology, Structure, Function Springer Verlag, Berlin, Heidelberg, New York 2001. ISBN 3-540-66239-1 .
  6. ^ Keyword "Loiasis" in the Pschyrembel Dictionary Sexuality. Walter de Gruyter, Berlin 2006; Pp. 893-894. ISBN 3-11-016965-7 .
  7. ↑ a b Keyword "Ochozercose" in Pschyrembel Dictionary Sexuality. Walter de Gruyter, Berlin 2006; P. 1104. ISBN 3-11-016965-7 .

literature

  • Gerhard Hartwich : Tribe Nemathelminthes or Aschelminthes - tube worms. Urania Tierreich, Volume Invertebrates 1, Urania Verlag Berlin 2000; P. 353 ff. ISBN 3-332-01174-X

Web links

Commons : Filarioidea  - collection of images, videos and audio files