anopheles

from Wikipedia, the free encyclopedia
anopheles
Anopheles sucking blood

Anopheles sucking blood

Systematics
Class : Insects (Insecta)
Order : Fly (Diptera)
Subordination : Mosquitoes (Nematocera)
Family : Mosquitoes (Culicidae)
Subfamily : Anophelinae
Genre : anopheles
Scientific name
anopheles
Meigen , 1818
Subgenera

Anopheles ( ancient Greek ανοφελός anophelós , German 'useless, arduous, harmful' ), also called malaria , fork or fever mosquito , is a genus in the mosquito family(Culicidae) and gives its name to the subfamily Anophelinae . The genus comprises around 420 species, of which around 40 species can be carriers of malaria worldwide. At around six millimeters, malaria mosquitoes are relatively small and have a slim build, but they can still be easily recognized by their posture: the body is usually at an angle of around 30 to 45 ° to the ground. There are numerous species and subspecies, some of which can only be distinguished by specialists due to their great similarity.

Occurrence

Representatives of the genus Anopheles can be found worldwide in tropical and subtropical locations as well as in areas of moderate temperatures. This excludes most of the islands in the Pacific (including New Zealand , Fiji, and New Caledonia ) as well as some isolated islands in the Atlantic .

features

Adult Anopheles species can usually be recognized by their characteristic posture, in which they place their bodies largely straight and usually at an angle of 30 to 45 ° to the ground. Mosquitoes of the genus Anopheles can also be distinguished from other mosquito species on the basis of their entire, evenly round back shield ( scutellum ). The back label is provided with a continuous row of bristles. Anopheles females have long buttons ( palps ) and a one-piece seed capsule ( receptaculum seminis or spermatheke).

Development cycle

Anopheles larva from a southern German garden pond.
Larva turning head.

In almost all species, the development cycle of the Anopheles mosquitoes is tied to stagnant water of all sizes - the smallest ponds, knotholes or hoof prints that carry water for 5 to 14 days (development time of the larvae, depending on the species and temperature) are enough for some species. A female lays between 50 and 200 small, black-colored eggs. They have floats that prevent them from sinking. If the water dries up, the eggs also die. In warm weather the larvae hatch after 2–3 days, in cold weather it can take 2–3 weeks.

The larvae do not have a breathing tube . Instead, there is a breathing opening on the 8th segment of the body. The larvae adhere to the water surface with water-repellent hairs (palm hairs) and thus hang parallel to the water surface (like Dixa ) - a distinguishing feature from the mosquitoes of the subfamily Culicinae . They submerge in danger, but have to return to the surface to breathe. The larvae feed on microorganisms and algae, which they filter from the water. The larvae can turn their head by 180 ° in order to take up food particles on the surface of the water (see film opposite). The larva goes through 4 moltings before it turns into a pupa. After a few days as a doll , the transformation is complete and a new mosquito hatches.

The males gather in shoals, which are sought by the females in search of a partner.

nutrition

Male and female Anopheles mosquitoes feed on plant saps. However, after fertilization by males, females also need at least one human or animal blood meal to take in protein so that ovaries can develop. Two to three days after hatching, the female anopheles usually looks for a victim for the first blood meal after dark or in the early morning hours in the house or in the great outdoors and then lays the eggs after another two to three days.

Their stings are usually accompanied by swelling and severe itching . They itch more than, for example, the common mosquito that is most common in Germany .

However, the habits of the individual Anopheles species are very different, so that there are also species that generally disdain human blood:

  • Anopheles atroparvus : endophilous (stings in buildings and outdoors), but prefers livestock, but also sucks on humans, especially at high temperatures and low relative humidity
  • Anopheles maculipennis : endophilous (stings in buildings and outdoors), pets are the preferred source of food
  • Anopheles plumbeus : exophil (stings outdoors), especially in forests and parks, blood donors are wild animals and domestic animals, only rarely humans

The Anopheles mosquito as a disease vector

Before the Anopheles mosquito, like all other blood-sucking insects , picks up her food, injected them with their proboscis ( proboscis ) a glandular secretion (in general, saliva ) in their victim into it. This secretion mainly contains an active ingredient that is supposed to prevent possible blood clotting in your trunk while you are eating. In addition, the blood flow to the puncture site is increased. For the "victim" (e.g. human) the injected mosquito saliva is a foreign body, the immune system reacts to it, it itches and burns for more or less long at the point of the bite and a wheal forms . This saliva can also contain pathogens ( viruses , bacteria , unicellular or multicellular parasites ) that the mosquito ingested with the blood of an infected victim when it was previously ingested. If these pathogens not only survive in the mosquito, but also multiply and / or change in it, then the mosquito is a host or intermediate host for these pathogens and infects their next food victim in the manner already described. As a vector, the Anopheles mosquito is therefore the biological carrier of tropical diseases ( malaria , filariasis and viral diseases such as O'nyong-nyong fever ). For the transmission of malaria, caused by spore animals of the genus Plasmodium parasitizing in the red blood cells , a minimum temperature over a longer period is required (16 ° C summer isotherm for Plasmodium vivax , the most insensitive to cold plasmodium species).

Potentially, as with all vectors, also a mechanical transmission of all possible excitation here through the outer and inner contamination of the proboscis (of the piercing, proboscis ) of the Anopheles possible if the insect is disturbed during the food intake in an infected person and immediately on another uninfected person continues to suckle. Based on current knowledge, it is to be expected that this possibility of transmission, if at all, can only occur occasionally in populations with a very high spread of the pathogen. This transmission path corresponds to that of infection by needle stick injury or injection cannulas used several times in succession without intervening sterilization , but on a different scale. Theoretically, the transmission of a single pathogen can cause infection in this way. In practice, however, a sufficient minimum amount of pathogens is required for infection. It is questionable whether this minimum amount can be achieved on its own, for example in the case of contamination of the Anophelesproboscis. Epidemiologically, there are no clear signs of this type of transmission, at least in Anopheles, as in all other mosquitoes .

Spread of malaria

According to some scientists, the spread of Anopheles in some regions is promoted by deforestation and certain types of agriculture.

In Kenya , malaria has a basic multiplication rate of around 1900. A person who is infected with malaria theoretically infects 1900 other people there, if no one is immunized. However, in Punjab , a region of India , the exact same malaria pathogen Plasmodium falciparum has a basic reproduction rate of only 1.4. There are several reasons for this.

In Kenya, the species Anopheles gambiae has a survival probability of 95%, the Indian mosquito Anopheles culicifacies only 75%. In India, half of the infected mosquitoes died after around 2.5 days, and in Kenya only after 12 days. In both cases, the stages of the pathogen living in the mosquito need 12 days at 24-25 ° C to be ripe for the next infection.

Another difference is that Anopheles gambiae has to suck blood every two days and 100 percent stings people. On. culicifacies only sting every three days, and only ten percent people. Although mosquitoes are far more numerous in Indian endemic areas (by a factor of 20), malaria in Punjab is a relatively easy problem to control.

species

The following six Anopheles species are native to Germany:

The last three named species belong to the " Anopheles maculipennis group".

Other types:

See also

Web links

Wiktionary: Malaria mosquito  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Erwin J. Hentschel, Günther H. Wagner: Zoological dictionary . Gustav Fischer, Jena 1996, ISBN 3-334-60960-X .
  2. ↑ RE Harbach: genus Anopheles Meigen, 1818 , access on 10 June 2012 found.
  3. ↑ Heinz-Werner Baer: Anopheles and Malaria in Thuringia. Gustav Fischer, Jena 1960.
  4. ^ Centers for Disease Control and Prevention: Anopheles Mosquitoes . On: cdc.gov of October 21, 2015; last accessed on August 30, 2016.
  5. ↑ Wolf-Dieter Müller-Jahncke : Anopheles mosquito. In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 66 f.
  6. ↑ vu-wien.ac.at ( Memento from March 28, 2010 in the Internet Archive )
  7. ↑ vu-wien.ac.at ( Memento from June 18, 2009 in the Internet Archive )
  8. ^ Verena Winiwarter, Martin Knoll: Environmental history. An introduction (= UTB. Volume 2521). Böhlau, Cologne 2007, ISBN 978-3-8252-2521-6 , p. 247.
  9. ↑ Parasitology and Parasitism - 6. How are parasites distributed in different host populations and how do they spread in them? 6.14 answer . On: infektionsbiologie.ch ; last accessed on August 30, 2016.
  10. ↑ Parasitology and Parasitism - How are parasites distributed in different host populations and how do they spread in them? 6.12 Transmission and spread of malaria . On: infektionsbiologie.ch ; last accessed on August 30, 2016.
  11. ↑ Parasitology and Parasitism - 6. How are parasites distributed in different host populations and how do they spread in them? 6.13 Exercise: Comparison of malaria in two endemic areas . On: infektionsbiologie.ch ; last accessed on August 30, 2016.