Blood-sucking insects

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The Asian tiger mosquito ( Stegomyia albopicta ), among other things a carrier of dengue fever and chikungunya .

Blood-sucking insects are around 14,000 species of haematophagous insects from very different orders and families , whose diet consists partly or exclusively of the blood of other living things. They do not form a systematic unit, but a group whose similarities are the result of a similar way of life ( convergence ). The food sacrifices include reptiles, birds and mammals and thus also humans; very rarely are amphibians host species , in one case, a fish species (the mosquito Uranotaenia lateralis during mudskippers ).

Affiliation

The blood-sucking insects include (sorted according to orders / subordinate orders and families ):

Ticks (Ixodida) also suck blood, but do not belong to the insects (Insecta), but to the arachnids (Arachnida).

features

Characteristic of all blood-sucking insects is either a proboscis with which the skin of the host is pierced and serves as a suction tube ( capillary suction device ) or a coarser mouth tool with which the skin of the host is torn open ( pool suction device ). The structure of the respective oral limbs involved is very different depending on the systematic affiliation. In addition to the mouthparts, bloodsuckers need a special repertoire of enzymes for blood absorption and digestion. A prerequisite, for example, are enzymes that prevent the blood from clotting. Blood as a nutritional substance has a number of difficulties, including the heme component of the blood pigment hemoglobin, if it occurs freely in high concentrations, is a cell poison.

Several ecologically distinct groups can be distinguished among the blood-sucking insects.

  • in a number of two-winged families ( mosquitoes , black flies , midges , sandflies , horseflies ) only the females suck blood in order to be able to lay their eggs with this high-energy supplement. These are flying species that visit their hosts only briefly during the stinging process (a few minutes). The host specificity is usually low, but there are widespread specializations in birds or mammals as a group. The sucking process and the laying of eggs are usually coordinated with one another in such a way that one blood meal is sufficient for one clutch ("gonotrophic cycle"). Depending on the species, food is also consumed at different times of the day, but mostly away from intense sunlight during dawn, dusk or at night.
  • Flat bugs , blood-sucking predatory bugs, and many species of fleas regularly inhabit their hosts' nests and burrows (including stables and human housing). They usually suckle their hosts more often, but leave them immediately after sucking. The specialization of these species usually takes place more on the structure and the microclimate of the nest than on the host species. Mammals living in burrows have z. B. often similar parasite species.
  • many louse flies and bat flies and other flea species are free living but remain more permanent on a host once they have found it. Some only leave him to pupate and lay eggs. The larvae have a different way of life and do not suck blood.
  • permanent ectoparasites such as louse , some louse flies and bats living bugs family polyctenidae spend their entire lives on the host and lay their eggs. Re-infection is only possible through direct physical contact, as the animals quickly starve to death away from their host (sometimes after 6 hours). Permanent ectoparasites are usually highly host specific. Human lice, for example, live exclusively on humans. They can only be transferred to other hosts (e.g. rabbits) in the laboratory. Many species feed on false hosts when hungry for a long time, but cannot develop here and sometimes perish after a meal.

Blood-sucking insects as vectors of disease

Blood-sucking insects as parasites are biological and mechanical carriers ( vectors ) of viruses , bacteria , unicellular and multicellular cells and are of particular importance due to the infectious diseases that are triggered .

The blood-sucking insects are often not the main host for these pathogens ; as vectors, intermediate hosts or transport hosts , they usually transmit the pathogens to the main hosts of the pathogen reservoir and to other secondary hosts .

As vectors, blood-sucking insects can transmit pathogens in two different ways:

Biological transmission

This specific path is epidemiologically significant and immediately noticeable.

A single, specific species of pathogen (sometimes several) survives after ingestion in an infected person only in a special insect species within the insect body in the active state, can possibly also multiply and / or transform and infects the next time the same insect ingests in the case of a person not yet infected, this new victim . As a rule, only those blood-sucking insects come into consideration as biological transmitters, in which the pathogen multiplies in their body, which then either after migration through the hemolymph into the saliva before the start of blood uptake during saliva release, or after development in the intestine be released into the victim to be aspirated by regurgitation before or during blood intake. Basically, in this way, blood-sucking insects can only transmit their specific pathogen.

Examples: Viruses transmitted by mosquito bites in Europe are the sand fly virus and the Sindbis virus . In North America the common mosquito (Culex pipiens) has been identified as a biological vector of the West Nile virus . In the tropics, however, different mosquitoes are known to be biological carriers of various pathogens and the diseases they cause in humans (and animals).

Mechanical transmission

This transmission path is usually very unspecific.

A mechanical transmission of all possible excitation here through the outer and inner potentially, as with all vectors, contamination of the proboscis (of the piercing, proboscis bloodsucking) Insect possible if the insect is disturbed during the food intake in an infected person and immediately on another uninfected person continues to suckle. According to the current state of knowledge, it is to be expected that this possibility of transmission can only occasionally occur, if at all, in populations with a very high spread of the pathogen.

This transmission path corresponds to that of infection by needle stick injuries or injection cannulas used several times in a row without sterilization in between , 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. Whether this minimum amount z. B. can be achieved in a contamination of the mosquito bugs alone is questionable.

The nocturnal, blood-sucking butterfly and moth species Calyptra eustrigata , Calyptra labilis , Calyptra minuticornis , Calyptra orthograpta and Calyptra thalictri of the family Noctuidae and order Lepidoptera from South-East Asia are sufficient for a mechanical transmission of various pathogens . With its proboscis, transformed from a suction proboscis into a proboscis , these moths penetrate up to seven millimeters into the skin of mammals, including humans, and then suck the blood for a maximum of one hour. In the event of defensive movements, they are always ready to leave their victim before they have reached satiety , so that they can continue to eat as soon as a new one is received. Other butterfly species such as Lobocraspis griseifulva , Arcyophora spp. and Filodes fulvidorsalis of the families Pyralidae , Noctuidae and Geometridae from Africa, Brazil and South-East Asia ingest tear fluid in mammals and humans. With their suction problems, which are rough on the outside, they rub the eyeball to cause an increase in tear production and can also cause minor injuries to the eyeball. All these types of butterflies are thus clearly recognized as mechanical carriers of various pathogens. Even the possibility of HIV transmission is being discussed.

Furthermore, as early as 1965, Luedke et al. a purely mechanical transmission of the bluetongue virus by arthropods such. B. detected by the sheep louse fly ( Melophagus ovinus ).

Kenneth Gage et al. from the National Center for Infectious Diseases have shown the occasional mechanical transmission of the bubonic plague pathogen , the bacterium Yersinia pestis , in human fleas ( Pulex irritans ) .

It is not only in Africa that brakes are responsible for the mechanical transmission of anthrax , Weil's disease and tularemia to humans. Since in particular, horseflies ( Tabanus sudeticus ) and stable flies (Stomoxys) arriving at the lentiviruses belonging EIA virus can be transferred to mechanical way, there is a theoretical possibility that through this large blood-sucking insects which also at the same genus belonging HI-virus in this Paths can be transmitted. The suction pipe of this insect species is large enough, each of these type of virus in a sufficient amount of an infection in an injection s cannula to store temporarily the inside and outside. However, no such cases of transmission have been reported with the HI virus.

See also

Parasites of humans

Individual evidence

  1. ↑ JM Ribeiro: Blood-feeding arthropods: live syringes or invertebrate pharmacologists? In: Infectious agents and disease. Vol. 4, No. 3, 1995, pp. 143-152, PMID 8548192 .
  2. ↑ see for example. Gholamreza Darai, Michaela Handermann, Hans-Günther Sonntag u. a .: Lexicon of infectious diseases in humans: pathogens, symptoms, diagnosis, therapy and prophylaxis; with 43 tables. 3rd edition, Springer Science & Business Media, Heidelberg 2009, ISBN 978-3-540-39005-3 , p. 256: Transmission / vectors. ( at google books )
  3. ^ H. Bänziger: Skin-piercing blood-sucking moths I: ecological and ethological studies on Calpe eustrigata (Lepid., Noctuidae). In: Acta tropica. Volume 32, Number 2, 1975, pp. 125-144, ISSN  0001-706X , PMID 240258 .
  4. ^ H. Bänziger: Skin-piercing blood-sucking moths II: Studies on a further 3 adult Calyptra [Calpe] sp. (Lepid., Noctuidae). In: Acta tropica. Volume 36, Number 1, March 1979, pp. 23-37, ISSN  0001-706X , PMID 35931 .
  5. ^ Sylvia Koslowsky: Bluetongue Disease in Germany? Dissertation, FU Berlin 2002 urn : nbn: de: kobv: 188-2002002336 .
  6. ^ Gage KL .: Factors affecting the spread and maintenance of plague. In: Adv Exp Med Biol. 2012, No. 954, pp. 79-94, PMID 22782750 .
  7. ↑ Steven W. Luger: Lyme Disease Transmitted by a Biting Fly. In: The New England Journal of Medicine June 14, 1990, Vol. 322, No. 24, p. 1752, p. 1752 (Correspondence), doi : 10.1056 / NEJM199006143222415 .
  8. ↑ Equine infectious anemia / transmission. On: fli.bund.de from May 31, 2007 ( Memento from June 10, 2007 in the Internet Archive )