Wikipedia

Disease vector

Inepidemiology,adisease vectoris any living[1]agent that carries and transmits an infectiouspathogensuch as aparasiteor microbe, to another living organism.[2][3]Agents regarded as vectors are mostly blood-sucking insects such as mosquitoes. The first major discovery of a disease vector came fromRonald Rossin 1897, who discovered themalariapathogen when he dissected the stomach tissue of amosquito.[4][5][dead link‍]

Amosquitoshortly after obtaining blood from a human (note the droplet of blood plasma being expelled as the mosquito squeezes out excess water). Mosquitos are a vector for several diseases, includingmalaria.

Arthropods

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Thedeer tick,a vector forLyme diseasepathogens

Arthropodsform a major group of pathogen vectors withmosquitoes,flies,sand flies,lice,fleas,ticks,andmitestransmitting a huge number of pathogens. Many such vectors arehaematophagous,which feed on blood at some or all stages of their lives. When the insects feed on blood, the pathogen enters the blood stream of the host. This can happen in different ways.[6][7]

TheAnophelesmosquito, a vector formalaria,filariasis,and various arthropod-borne-viruses (arboviruses), inserts its delicate mouthpart under the skin and feeds on its host's blood. The parasites the mosquito carries are usually located in itssalivary glands(used by mosquitoes to anaesthetise the host). Therefore, the parasites are transmitted directly into the host's blood stream. Pool feeders such as thesand flyandblack fly,vectors for pathogens causingleishmaniasisandonchocerciasisrespectively, will chew a well in the host's skin, forming a small pool of blood from which they feed.Leishmaniaparasites then infect the host through the saliva of the sand fly.Onchocercaforce their own way out of the insect's head into the pool of blood.[8][9]

Triatomine bugsare responsible for the transmission of atrypanosome,Trypanosoma cruzi,which causesChagas disease.The Triatomine bugs defecate during feeding and the excrement contains the parasites, which are accidentally smeared into the open wound by the host responding to pain and irritation from the bite.[10][11][12][13]

There are several species ofThripsthat act as vectors for over 20 viruses, especiallyTospoviruses,and cause all sorts ofplant diseases.[14][15]

Plants and fungi

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Some plants and fungi act as vectors for various pathogens. For example, thebig-vein disease of lettucewas long thought to be caused by a member of the fungal divisionChytridiomycota,namelyOlpidium brassicae.Eventually, however, the disease was shown to be viral. Later it transpired that the virus was transmitted by thezoosporesof the fungus and also survived in the resting spores. Since then, many other fungi in Chytridiomycota have been shown to vector plant viruses.[16]

Many plant pests that seriously damage important crops depend on other plants, often weeds, to harbour or vector them; the distinction is not always clear. In the case ofPuccinia graminisfor example,Berberisand related genera act as alternate hosts in a cycle of infection of grain.[17]

More directly, when they twine from one plant to another, parasitic plants such asCuscutaandCassythahave been shown to conveyphytoplasmalandviral diseasesbetween plants.[18] [16]

Mammals

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Rabiesis transmitted through exposure to the saliva or brain tissue of an infected animal. Anywarm-bloodedanimal can carry rabies, but the most common vectors aredogs,skunks,raccoons,andbats.[19]

Vector-borne zoonotic disease and human activity

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This figure shows how theFlavivirusis carried bymosquitosin theWest Nile virusandDengue fever.The mosquito would be considered a disease vector.

Several articles, recent to early 2014, warn that human activities are spreading vector-bornezoonoticdiseases.[a]Several articles were published in the medical journalThe Lancet,and discuss how rapid changes inland use,trade globalization,climate changeand "social upheaval" are causing a resurgence in zoonotic disease across the world.[20]

Examples of vector-borne zoonotic diseases include:[21]

Many factors affect the incidence of vector-borne diseases. These factors include animals hosting the disease, vectors, and people.[21]

Humans can also be vectors for some diseases, such asTobacco mosaic virus,physically transmitting the virus with their hands from plant to plant.[citation needed]

Control and prevention

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Public health agencies educate people about many different disease vectors. This artwork, at theLondon School of Hygiene and Tropical Medicine,shows 10 different animal vectors.

TheWorld Health Organization(WHO) states that control and prevention of vector-borne diseases are emphasizing "Integrated Vector Management (IVM)",[22]which is an approach that looks at the links between health and environment, optimizing benefits to both.[b][23]

In April 2014, WHO launched a campaign called "Small bite, big threat" to educate people about vector-borne illnesses. WHO issued reports indicating that vector-borne illnesses affect poor people, especially people living in areas that do not have adequate levels of sanitation, drinking water and housing.[24]It is estimated that over 80% of the world's population resides in areas under threat of at least one vector borne disease.[25][26]

See also

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Notes

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  1. ^"Vector-borne zoonotic diseases are those that naturally infect wildlife and are then transmitted to humans through carriers, or vectors, such as mosquitoes or ticks."[20]
  2. ^"IVM strategies are designed to achieve the greatest disease control benefit in the most cost-effective manner, while minimizing negative impacts on ecosystems (e.g. depletion of biodiversity) and adverse side-effects on public health from the excessive use of chemicals in vector control."[23]

References

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  1. ^"Vector-borne diseases".
  2. ^"Vector".WordNetSearch 3.1.Princeton University.Retrieved7 April2014.
  3. ^Last, James, ed. (2001).A Dictionary of Epidemiology.New York:Oxford University Press.p. 185.ISBN978-0-19-514169-6.OCLC207797812.
  4. ^Muacevic, Alexander (2024-08-02)."The Legacy of Sir Ronald Ross: From Malaria Research to Multifaceted Achievements".National Library of Medicine.Retrieved2024-11-22.
  5. ^Prevention, CDC-Centers for Disease Control and (2017-03-28)."CDC - Malaria - About Malaria - History - Ross and the Discovery that Mosquitoes Transmit Malaria Parasites".www.cdc.gov.Retrieved2020-10-23.
  6. ^"Classification of Animal Parasites".plpnemweb.ucdavis.edu.Archived fromthe originalon 2017-10-06.Retrieved2016-02-25.
  7. ^Garcia, Lynne S. (August 15, 1999)."Classification of Human Parasites, Vectors, and Similar Organisms".Clinical Infectious Diseases.29(4): 734–736.doi:10.1086/520425.PMID10589879.
  8. ^"8.20D: Arthropods as Vectors".23 June 2017.
  9. ^"PEOI Foundations of Public Health".
  10. ^"CDC - Chagas Disease - Detailed Fact Sheet".11 April 2022.
  11. ^"Coronavirus disease 2019 (COVID-19) from Mayo Clinic - Mayo Clinic".Mayo Clinic.
  12. ^"CDC - Chagas Disease - General Information".13 April 2022.
  13. ^"Chagas disease".
  14. ^"Thripidae - an overview | ScienceDirect Topics".
  15. ^"Thysanoptera - an overview | ScienceDirect Topics".
  16. ^abR. S. Mehrotra (2013).Fundamentals of Plant Pathology.Tata McGraw-Hill Education. pp. 342–.ISBN978-1-259-02955-4.
  17. ^Peter W. Price (1980).Evolutionary Biology of Parasites.Princeton University Press.pp. 61–.ISBN0-691-08257-X.
  18. ^Haynes, A R. et al. Comparison of two parasitic vines: Dodder (Cuscuta) and Woe vine(Cassytha). Florida Dept Agric & Consumer Services. Division of Plant Industry. Botany Circular No. 30. January/February 1996
  19. ^"Raccoons and public health".The Humane Society of the United States.Retrieved2022-04-01.
  20. ^abPurlain, Ted (5 December 2012)."Lancet addresses emerging infectious vector-borne diseases".Vaccine News Daily.Chicago, Illinois.Retrieved7 April2014.
  21. ^abUniversity of California - Santa Cruz (30 November 2012)."Emerging vector-borne diseases create new public health challenges".Science Daily.Rockville, Maryland.Retrieved7 April2014.
  22. ^"Handbook for Integrated Vector Management"(PDF).World Health Organization.Retrieved3 December2015.
  23. ^ab"Vector-borne disease".The Health and Environment Linkages Initiative (HELI).Geneva, Switzerland: World Health Organization.Retrieved7 April2014.
  24. ^Parrish, Ryan (7 April 2014)."WHO focuses on vector-borne diseases for World Health Day 2014".Vaccine News Daily.Chicago,Illinois.Retrieved7 April2014.
  25. ^"Vector-borne diseases".www.who.int.Retrieved2023-03-31.
  26. ^Qureshi, Yasser M.; Voloshin, Vitaly; Facchinelli, Luca; McCall, Philip J.; Chervova, Olga; Towers, Cathy E.; Covington, James A.; Towers, David P. (2023-03-21)."Finding a Husband: Using Explainable AI to Define Male Mosquito Flight Differences".Biology.12(4): 496.doi:10.3390/biology12040496.ISSN2079-7737.PMC10135534.PMID37106697.
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