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Mosquito

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Prior to and during blood feeding, they inject saliva into the bodies of their source(s) of blood. Female mosquitoes hunt their blood host by detecting carbon dioxide (CO2) and 1-octen-3-ol from a distance.

Aedes aegypti vector of dengue fever and yellow fever

Mosquitoes of the genus Toxorhynchites never drink blood.[1] This genus includes the largest extant mosquitoes, the larvae of which prey on the larvae of other mosquitoes. These mosquito eaters have been used in the past as mosquito control agents, with varying success.[2]

Contents

[edit] Saliva

In order for the mosquito to obtain a blood meal it must surmount the vertebrate physiological responses. The mosquito, as with all blood-feeding arthropods, has evolved mechanisms to effectively block the hemostasis system with their saliva, which contains a mixture of secreted proteins. Mosquito saliva affects vascular constriction, blood clotting, platelet aggregation, inflammation, immunity, and angiogenesis.[3] Universally, hematophagous arthropod saliva contains at least one anticlotting, one anti-platelet, and one vasodilatory substance. Mosquito saliva also contains enzymes that aid in sugar feeding[4] and antimicrobial agents to control bacterial growth in the sugar meal.[5] The composition of mosquito saliva is relatively simple as it usually contains fewer than 20 dominant proteins.[6] Despite the great strides in knowledge of these molecules and their role in bloodfeeding achieved recently, scientists still cannot ascribe functions to more than half of the molecules found in arthropod saliva.[6] One promising application is the development of anti-clotting drugs based on saliva molecules, which might be useful for approaching heart-related disease, because they are more user-friendly blood clotting inhibitors and capillary dilators.[7]

It is now well recognized that the feeding ticks, sandflies, and, more recently, mosquitoes have an ability to modulate the immune response of the animals (hosts) they feed on.[3] The presence of this activity in vector saliva is a reflection of the inherent overlapping and interconnected nature of the host hemostatic and inflammatory/immunological responses and the intrinsic need to prevent these host defenses from disrupting successful feeding. The mechanism for mosquito saliva-induced alteration of the host immune response is unclear, but the data has become increasingly convincing that such an effect occurs. Early work described a factor in saliva that directly suppresses TNF-α release, but not antigen-induced histamine secretion, from activated mast cells.[8] Experiments by Cross et al. (1994) demonstrated that the inclusion of Ae. aegypti mosquito saliva into naïve cultures led to a suppression of interleukin (IL)-2 and IFN-γ production, while the cytokines IL-4 and IL-5 are unaffected by mosquito saliva.[9] Cellular proliferation in response to IL-2 is clearly reduced by prior treatment of cells with SGE.[9] Correspondingly, activated splenocytes isolated from mice fed upon by either Ae. aegypti or Cx. pipiens mosquitoes produce markedly higher levels of IL-4 and IL-10 concurrent with suppressed IFN-γ production.[10] Unexpectedly, this shift in cytokine expression is observed in splenocytes up to 10 days after mosquito exposure, suggesting that natural feeding of mosquitoes can have a profound, enduring, and systemic effect on the immune response.[10]

T cell populations are decidedly susceptible to the suppressive effect of mosquito saliva, showing enhanced mortality and decreased division rates.[11] Parallel work by Wasserman et al. (2004) demonstrated that T- and B-cell proliferation was inhibited in a dose dependent manner with concentrations as low as 1/7th of the saliva in a single mosquito.[12] Depinay et al. (2005) observed a suppression of antibody-specific T cell responses mediated by mosquito saliva and dependent on mast cells and IL-10 expression.[13] A recent study suggests that mosquito saliva can also decrease expression of interferon−α/β during early mosquito-borne virus infection.[14] The contribution of type I interferons (IFN) in recovery from infection with viruses has been demonstrated in vivo by the therapeutic and prophylactic effects of administration of IFN-inducers or IFN,[15] and recent research suggests that mosquito saliva exacerbates West Nile virus infection,[16] as well as other mosquito-transmitted viruses.[17]

[edit] Egg development and blood digestion

Two important events in the life of female mosquitoes are egg development and blood digestion. After taking a blood meal the midgut of the female synthesizes proteolytic enzymes that hydrolyze the blood proteins into free amino acids. These are used as building blocks for the synthesis of egg yolk proteins.

In the mosquito Anopheles stephensi Liston, trypsin activity is restricted entirely to the posterior midgut lumen. No trypsin activity occurs before the blood meal, but activity increases continuously up to 30 hours after feeding, and subsequently returns to baseline levels by 60 hours. Aminopeptidase is active in the anterior and posterior midgut regions before and after feeding. In the whole midgut, activity rises from a baseline of approximately 3 enzyme units (EU) per midgut to a maximum of 12 EU at 30 hours after the blood meal, subsequently falling to baseline levels by 60 hours. A similar cycle of activity occurs in the posterior midgut and posterior midgut lumen, whereas aminopeptidase in the posterior midgut epithelium decreases in activity during digestion. Aminopeptidase in the anterior midgut is maintained at a constant low level, showing no significant variation with time after feeding. alpha-glucosidase is active in anterior and posterior midguts before and at all times after feeding. In whole midgut homogenates, alpha-glucosidase activity increases slowly up to 18 hours after the blood meal, then rises rapidly to a maximum at 30 hours after the blood meal, whereas the subsequent decline in activity is less predictable. All posterior midgut activity is restricted to the posterior midgut lumen. Depending upon the time after feeding, greater than 25% of the total midgut activity of alpha-glucosidase is located in the anterior midgut. After blood meal ingestion, proteases are active only in the posterior midgut. Trypsin is the major primary hydrolytic protease and is secreted into the posterior midgut lumen without activation in the posterior midgut epithelium. Aminopeptidase activity is also luminal in the posterior midgut, but cellular aminopeptidases are required for peptide processing in both anterior and posterior midguts. Alpha-glucosidase activity is elevated in the posterior midgut after feeding in response to the blood meal, whereas activity in the anterior midgut is consistent with a nectar-processing role for this midgut region.[18]

[edit] Distribution

A mosquito inside a home in Victoria, Australia

While many species are native to tropical and subtropical regions, some such as Aedes have successfully adapted themselves to cooler regions. In the warm and humid tropical regions, they are active the entire year long; however, in temperate regions they hibernate over winter. Eggs from strains in the temperate zones are more tolerant to the cold than ones from warmer regions.[19][20] They can even tolerate snow and temperatures under freezing. In addition, adults can survive throughout winter in suitable microhabitats.[21]

[edit] Means of dispersal

Over large distances the worldwide distribution is carried out primarily through sea routes, in which the eggs, larvae, and pupae in combination with water-filled used tires and cut flowers are transported around. As with sea transport, the transport of mosquitoes in personal vehicles, delivery trucks, and trains plays an important role.

[edit] Disease

Main article: mosquito-borne disease

Mosquitoes are a vector agent that carries disease-causing viruses and parasites from person to person without catching the disease themselves.

Anopheles albimanus mosquito feeding on a human arm. This mosquito is a vector of malaria and mosquito control is a very effective way of reducing the incidence of malaria.

The principal mosquito borne diseases are the viral diseases yellow fever and dengue fever, transmitted mostly by the Aedes aegypti, and malaria carried by the genus Anopheles. Though originally a public health concern, HIV is now thought to be almost impossible for mosquitoes to transmit[citation needed].

Mosquitoes are estimated to transmit disease to more than 700 million people annually in Africa, South America, Central America, Mexico and much of Asia with millions of resulting deaths.

Methods used to prevent the spread of disease, or to protect individuals in areas where disease is endemic include Vector control aimed at mosquito eradication, disease prevention, using prophylactic drugs and developing vaccines and prevention of mosquito bites, with insecticides, nets and repellents. Since most such diseases are carried by "elderly" females, scientists have suggested focusing on these to avoid the evolution of resistance[22]

[edit] Control

 This section may require cleanup to meet Wikipedia's quality standards. Please improve this section if you can. (December 2008)
Main article: Mosquito control
Larvae in stagnant water
Mosquito killed by hand swatting

There are many methods used for mosquito control. Depending on the situation, source reduction, biocontrol, larviciding (control of larvae), or adulticiding (control of adults) may be used to manage mosquito populations.

These techniques are accomplished using habitat modification, such as removing stagnant water and other breeding areas, pesticide like DDT, natural predators, (eg Dragonflies, larvae-eating fish), and trapping. Garlic Oil concentrate will repel mosquitos for up to 4 weeks.

[edit] Natural predators

Dragonflies are natural predators of mosquitoes.

The dragonfly eats mosquitoes at all stages of development and is quite effective in controlling populations.[23] Although bats and Purple Martins can be prodigious consumers of insects, many of which are pests, less than 1% of their diet typically consists of mosquitoes. Neither bats nor Purple Martins are known to control or even significantly reduce mosquito populations.[24] Some cyclopoid copepods are predators on 1st instar larvae, killing up to 40 Aedes larvae per day.[25] Larval Toxorhynchites mosquitoes are known as natural predators of other Culicidae. Each larva can eat an average of 10 to 20 mosquito larvae per day. During its entire development, a Toxorhynchites larva can consume an equivalent of 5,000 larvae of the first instar (L1) or 300 fourth instar larvae (L4) (Steffan & Evenhuis, 1981; Focks, 1982). However, Toxorhynchites can consume all types of prey, organic debris (Steffan & Evenhuis, 1981), or even exhibit cannibalistic behavior. A number of fish are also known to consume mosquito larvae, including bass, bluegill, catfish, fathead minnows, the western mosquitofish (Gambusia affinis), goldfish, guppies, and killifish.

Also, Bacillus thuringiensis israelensis has been used to control them as a biological agent.[citation needed]

[edit] Treatment of mosquito bites

Visible, irritating bites are due to an immune response from the binding of IgG and IgE antibodies to antigens in the mosquito's saliva. Some of the sensitizing antigens are common to all mosquito species, whereas others are specific to certain species. There are both immediate hypersensitivity reactions (Types I & III) and delayed hypersensitivity reactions (Type IV) to mosquito bites (see Clements, 2000).

There are several commercially available anti-itch medications, including those taken orally, such as Benadryl, or topically applied antihistamines and, for more severe cases, corticosteroids such as hydrocortisone and triamcinolone. Many home remedies exist, including calamine lotion. Ammonia has been clinically demonstrated to be an effective treatment.[26] Both using a brush to scratch the area surrounding the bite and running scalding hot water (around 49 °C) over it can alleviate itching for several hours by reducing histamine-induced skin blood flow.[27] On the other hand, excessive scratching can irritate the bite and break the skin, leading to prolonged recovery and the possibility of infection or scarring.[citation needed]

[edit] Cultural views

A mosquito in Baltic amber

According to the “Mosquitoes” chapter in Kwaidan: Stories and Studies of Strange Things, by Lafcadio Hearn (1850–1904), mosquitoes are seen as reincarnations of the dead, condemned by the errors of their former lives to the condition of Jiki-ketsu-gaki, or "blood-drinking pretas".[28]

[edit] Evolution

The Culicinae and Anopheles clades are believed to have diverged about 150 million years ago.[29] The Old and New World Anopheles species are believed to have subsequently diverged about 95 million years ago.[29]

[edit] Systematics

Main article: List of mosquito genera

There are approximately 3,500 species of mosquitoes grouped into 41 genera. Human malaria is transmitted only by females of the genus Anopheles. Of the approximately 430 Anopheles species, while over 100 are known to be able to transmit malaria to humans only 30-40 commonly do so in nature. Since breeding and biting habit differ considerably between species, species identification is important for control programmes.

[edit] See also

[edit] References

  1. ^ The carnivores, Toxorhynchites
  2. ^ http://www.pestscience.com/PDF/BNIra56.PDF
  3. ^ a b Ribeiro JM, Francischetti IM (2003). "Role of arthropod saliva in blood feeding: sialome and post-sialome perspectives". Annu. Rev. Entomol. 48: 73–88. doi:10.1146/annurev.ento.48.060402.102812. PMID 12194906. 
  4. ^ Grossman GL, James AA (1993). "The salivary glands of the vector mosquito, Aedes aegypti, express a novel member of the amylase gene family". Insect Mol. Biol. 1 (4): 223–32. doi:10.1111/j.1365-2583.1993.tb00095.x. PMID 7505701. 
  5. ^ Rossignol PA, Lueders AM (1986). "Bacteriolytic factor in the salivary glands of Aedes aegypti". Comp. Biochem. Physiol., B 83 (4): 819–22. doi:10.1016/0305-0491(86)90153-7. PMID 3519067. 
  6. ^ a b Valenzuela JG, Pham VM, Garfield MK, Francischetti IM, Ribeiro JM (2002). "Toward a description of the sialome of the adult female mosquito Aedes aegypti". Insect Biochem. Mol. Biol. 32 (9): 1101–22. doi:10.1016/S0965-1748(02)00047-4. PMID 12213246. 
  7. ^ Dr. Nigel Beebe, University of Technology, Sidney, Australia
  8. ^ Bissonnette EY, Rossignol PA, Befus AD (1993). "Extracts of mosquito salivary gland inhibit tumour necrosis factor alpha release from mast cells". Parasite Immunol. 15 (1): 27–33. doi:10.1111/j.1365-3024.1993.tb00569.x. PMID 7679483. 
  9. ^ a b Cross ML, Cupp EW, Enriquez FJ (1994). "Differential modulation of murine cellular immune responses by salivary gland extract of Aedes aegypti". Am. J. Trop. Med. Hyg. 51 (5): 690–6. PMID 7985763. 
  10. ^ a b Zeidner NS, Higgs S, Happ CM, Beaty BJ, Miller BR (1999). "Mosquito feeding modulates Th1 and Th2 cytokines in flavivirus susceptible mice: an effect mimicked by injection of sialokinins, but not demonstrated in flavivirus resistant mice". Parasite Immunol. 21 (1): 35–44. doi:10.1046/j.1365-3024.1999.00199.x. PMID 10081770. 
  11. ^ Wanasen N, Nussenzveig RH, Champagne DE, Soong L, Higgs S (2004). "Differential modulation of murine host immune response by salivary gland extracts from the mosquitoes Aedes aegypti and Culex quinquefasciatus". Med. Vet. Entomol. 18 (2): 191–9. doi:10.1111/j.1365-2915.2004.00498.x. PMID 15189245. 
  12. ^ Wasserman HA, Singh S, Champagne DE (2004). "Saliva of the Yellow Fever mosquito, Aedes aegypti, modulates murine lymphocyte function". Parasite Immunol. 26 (6-7): 295–306. doi:10.1111/j.0141-9838.2004.00712.x. PMID 15541033. 
  13. ^ Depinay N, Hacini F, Beghdadi W, Peronet R, Mécheri S (2006). "Mast cell-dependent down-regulation of antigen-specific immune responses by mosquito bites". J. Immunol. 176 (7): 4141–6. PMID 16547250. 
  14. ^ Schneider BS, Soong L, Zeidner NS, Higgs S (2004). "Aedes aegypti salivary gland extracts modulate anti-viral and TH1/TH2 cytokine responses to sindbis virus infection". Viral Immunol. 17 (4): 565–73. doi:10.1089/vim.2004.17.565. PMID 15671753. 
  15. ^ Taylor JL, Schoenherr C, Grossberg SE (1980). "Protection against Japanese encephalitis virus in mice and hamsters by treatment with carboxymethylacridanone, a potent interferon inducer". J. Infect. Dis. 142 (3): 394–9. PMID 6255036. 
  16. ^ Schneider BS, Soong L, Girard YA, Campbell G, Mason P, Higgs S (2006). "Potentiation of West Nile encephalitis by mosquito feeding". Viral Immunol. 19 (1): 74–82. doi:10.1089/vim.2006.19.74. PMID 16553552. 
  17. ^ Schneider BS, Higgs S (May 2008). "The enhancement of arbovirus transmission and disease by mosquito saliva is associated with modulation of the host immune response". Trans. R. Soc. Trop. Med. Hyg. 102 (5): 400–8. doi:10.1016/j.trstmh.2008.01.024. PMID 18342898. http://linkinghub.elsevier.com/retrieve/pii/S0035-9203(08)00053-9. 
  18. ^ Billingsley PF, Hecker H (1991). "Blood digestion in the mosquito, Anopheles stephensi Liston (Diptera: Culicidae): activity and distribution of trypsin, aminopeptidase, and alpha-glucosidase in the midgut". J Med Entomol. 28 (6): 865–71. PMID 1770523. 
  19. ^ Hawley WA, Pumpuni CB, Brady RH, Craig GB (March 1989). "Overwintering survival of Aedes albopictus (Diptera: Culicidae) eggs in Indiana". J. Med. Entomol. 26 (2): 122–9. PMID 2709388. 
  20. ^ Hanson SM, Craig GB (September 1995). "Aedes albopictus (Diptera: Culicidae) eggs: field survivorship during northern Indiana winters". J. Med. Entomol. 32 (5): 599–604. PMID 7473614. 
  21. ^ Romi R, Severini F, Toma L (March 2006). "Cold acclimation and overwintering of female Aedes albopictus in Roma". J. Am. Mosq. Control Assoc. 22 (1): 149–51. doi:10.2987/8756-971X(2006)22[149:CAAOOF]2.0.CO;2. PMID 16646341. 
  22. ^ Resistance is Useless The Economist 8-April-2009
  23. ^ Singh RK, Dhiman RC, Singh SP (June 2003). "Laboratory studies on the predatory potential of dragon-fly nymphs on mosquito larvae". J Commun Dis 35 (2): 96–101. PMID 15562955. 
  24. ^ Fradin MS (01 June 1998). "Mosquitoes and mosquito repellents: a clinician's guide". Ann. Intern. Med. 128 (11): 931–40. PMID 9634433. http://www.annals.org/cgi/pmidlookup?view=long&pmid=9634433. 
  25. ^ Marten GG, Reid JW (2007). "Cyclopoid copepods". J. Am. Mosq. Control Assoc. 23 (2 Suppl): 65–92. doi:10.2987/8756-971X(2007)23[65:CC]2.0.CO;2. PMID 17853599. 
  26. ^ Maibach, Howard I. "Mosquito Bite Therapy: Evidenced-Based". Exogenous Dermatology 3 (6): 332–338. doi:10.1159/000093650. http://karger.yakeworld.ddns.info/ProdukteDB/produkte.asp?Aktion=ShowPDF&ProduktNr=227090&Ausgabe=231745&ArtikelNr=93650&filename=93650.pdf. Retrieved on 2007-10-08. 
  27. ^ Yosipovitch, Gil; Katherine Fast, Jeffrey D. Bernhard. "Noxious Heat and Scratching Decrease Histamine-Induced Itch and Skin Blood Flow". Journal of Investigative Dermatology 2005 (125): 1268–1272. doi:10.1111/j.0022-202X.2005.23942.x. http://www.nature.com/jid/journal/v125/n6/pdf/5603667a.pdf. Retrieved on 2009-05-30. 
  28. ^ Hearn, Lafcadio. Kwaidan: Stories and Studies of Strange Things. Dover Publications, Inc., 1968 (ISBN 0-486-21901-1)
  29. ^ a b Calvo E, Pham VM, Marinotti O, Andersen JF, Ribeiro JM (2009). "The salivary gland transcriptome of the neotropical malaria vector Anopheles darlingi is thought to reveal accelerated evolution of genes relevant to hematophagy" (PDF). BMC Genomics 10 (1): 57. doi:10.1186/1471-2164-10-57. http://www.biomedcentral.com/content/pdf/1471-2164-10-57.pdf. Retrieved on 2009-06-21. 
  • Clements, Alan (1992). The biology of mosquitoes. 1: Development, Nutrition and Reproduction. London: Chapman & Hall. ISBN 0-85199-374-5. 
  • Davidson, Elizabeth W. (1981). Pathogenesis of invertebrate microbial diseases. Montclair, N.J: Allanheld, Osmun. ISBN 0-86598-014-4. 
  • Jahn GC, Hall DW, Zam SG (1986). "A comparison of the life cycles of two Amblyospora (Microspora: Amblyosporidae) in the mosquitoes Culex salinarius and Culex tarsalis". Coquillett. J. Florida Anti-Mosquito Assoc. 57: 24–7. 
  • Kale, H.W., II. (1968). "The relationship of purple martins to mosquito control". The Auk 85: 654–61. 

[edit] Identification

  • Brunhes, J.; Rhaim, A.; Geoffroy, B. Angel G. Hervy P. Les Moustiques de l'Afrique mediterranéenne French/English. Interactive identification guide to mosquitoes of North Africa, with database of information on morphology, ecology, epidemiology, and control. Mac/PC Numerous illustrations. IRD/IPT [12640] 2000 CD-ROM. ISBN 2-7099-1446-8 Mosquito species can also be identified through their DNA, however this is relatively expensive so it is not commonly performed. See the Use of DNA in forensic entomology.

[edit] External links

 This article's external links may not follow Wikipedia's content policies or guidelines. Please improve this article by removing excessive or inappropriate external links. (June 2009)
Search Wikimedia Commons Wikimedia Commons has media related to: Culicidae
Search Wikispecies Wikispecies has information related to: Culicidae

[1]

[edit] References

  1. ^ vector
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