disease vector

File:Adult deer tick(cropped).jpg, a vector for Lyme disease pathogens]]

Arthropods form a major group of pathogen vectors with mosquitoes, flies, sand flies, lice, fleas, ticks, and mites transmitting a huge number of pathogens. Many such vectors are haematophagous, 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.{{cite web|url=http://plpnemweb.ucdavis.edu/nemaplex/General/animpara.htm|title=Classification of Animal Parasites|website=plpnemweb.ucdavis.edu|access-date=2016-02-25|archive-date=2017-10-06|archive-url=https://web.archive.org/web/20171006152348/http://plpnemweb.ucdavis.edu/nemaplex/General/animpara.htm|url-status=dead}}{{Cite journal |last=Garcia |first=Lynne S. |date=August 15, 1999 |title=Classification of Human Parasites, Vectors, and Similar Organisms |journal=Clinical Infectious Diseases |volume=29 |issue=4 |pages=734–736 |doi=10.1086/520425 |pmid=10589879 |doi-access=free}}

The Anopheles mosquito, a vector for malaria, 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 its salivary glands (used by mosquitoes to anaesthetise the host). Therefore, the parasites are transmitted directly into the host's blood stream. Pool feeders such as the sand fly and black fly, vectors for pathogens causing leishmaniasis and onchocerciasis respectively, will chew a well in the host's skin, forming a small pool of blood from which they feed. Leishmania parasites then infect the host through the saliva of the sand fly. Onchocerca force their own way out of the insect's head into the pool of blood.{{cite web | url=https://bio.libretexts.org/Bookshelves/Microbiology/Book%3A_Microbiology_(Boundless)/8%3A_Microbial_Evolution_Phylogeny_and_Diversity/8.20%3A_Helminths/8.20D%3A_Arthropods_as_Vectors | title=8.20D: Arthropods as Vectors | date=23 June 2017 }}{{cite web | url=https://www.peoi.org/Courses/Coursesen/phfoundation/contents/frame4a.html | title=PEOI Foundations of Public Health }}

Triatomine bugs are responsible for the transmission of a trypanosome, Trypanosoma cruzi, which causes Chagas 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.{{cite web | url=https://www.cdc.gov/parasites/chagas/gen_info/detailed.html | title=CDC - Chagas Disease - Detailed Fact Sheet | date=11 April 2022 }}{{cite web | url=https://www.mayoclinic.org/coronavirus-covid-19 | title=Coronavirus disease 2019 (COVID-19) from Mayo Clinic - Mayo Clinic | website=Mayo Clinic }}{{cite web | url=https://www.cdc.gov/parasites/chagas/gen_info/vectors/index.html | title=CDC - Chagas Disease - General Information | date=13 April 2022 }}{{cite web | url=https://www.who.int/news-room/fact-sheets/detail/chagas-disease-(american-trypanosomiasis) | title=Chagas disease }}

There are several species of Thrips that act as vectors for over 20 viruses, especially Tospoviruses, and cause all sorts of plant diseases.{{cite book | url=https://www.sciencedirect.com/topics/immunology-and-microbiology/thripidae | title=Thripidae - an overview | ScienceDirect Topics | chapter=Insects as transport devices of plant viruses | date=2020 | pages=381–402 | publisher=Elsevier | isbn=978-0-12-818654-1 }}{{cite book | url=https://www.sciencedirect.com/topics/immunology-and-microbiology/thysanoptera | title=Thysanoptera - an overview | ScienceDirect Topics | chapter=Plant RNA virus vector interactions in epidemiology of plant viral diseases | date=2023 | pages=329–348 | publisher=Elsevier | isbn=978-0-323-95339-9 }}

Some plants and fungi act as vectors for various pathogens. For example, the big-vein disease of lettuce was long thought to be caused by a member of the fungal division Chytridiomycota, namely Olpidium brassicae. Eventually, however, the disease was shown to be viral. Later it transpired that the virus was transmitted by the zoospores of the fungus and also survived in the resting spores. Since then, many other fungi in Chytridiomycota have been shown to vector plant viruses.{{cite book|author=R. S. Mehrotra|title=Fundamentals of Plant Pathology|url=https://books.google.com/books?id=5h_ZAgAAQBAJ&pg=PA342|year=2013|publisher=Tata McGraw-Hill Education|isbn=978-1-259-02955-4|pages=342–}}

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 of Puccinia graminis for example, Berberis and related genera act as alternate hosts in a cycle of infection of grain.{{cite book |author=Peter W. Price |url=https://books.google.com/books?id=rGO0QPfcFkMC&pg=PA61 |title=Evolutionary Biology of Parasites |publisher=Princeton University Press |year=1980 |isbn=0-691-08257-X |pages=61–}}

More directly, when they twine from one plant to another, parasitic plants such as Cuscuta and Cassytha have been shown to convey phytoplasmal and viral diseases between plants.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

Rabies is transmitted through exposure to the saliva or brain tissue of an infected animal. Any warm-blooded animal can carry rabies, but the most common vectors are dogs, skunks, raccoons, and bats.{{Cite web |title=Raccoons and public health |url=https://www.humanesociety.org/resources/raccoons-and-public-health |access-date=2022-04-01 |website=The Humane Society of the United States |language=en}}

File:Disease Vector.jpg is carried by mosquitos in the West Nile virus and Dengue fever. The mosquito would be considered a disease vector.]]

Several articles, recent to early 2014, warn that human activities are spreading vector-borne zoonotic diseases.{{efn|"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."{{cite news|last=Purlain|first=Ted|title=Lancet addresses emerging infectious vector-borne diseases|url=http://vaccinenewsdaily.com/medical_countermeasures/320968-lancet-addresses-emerging-infectious-vector-borne-diseases/|access-date=7 April 2014|newspaper=Vaccine News Daily|date=5 December 2012 |location=Chicago, Illinois}}}} Several articles published in the medical journal The Lancet, discussed how rapid changes in land use, trade globalization, climate change and "social upheaval" are causing a resurgence in zoonotic disease across the world. Displacement due to conflicts, migration, or population movements can create situations where people are more exposed to disease vectors. Additionally, human activities such as deforestation, agricultural expansion, urbanization, and increased trade and travel, are creating environments where vectors can thrive and spread diseases to humans more easily.{{Cite journal |last1=Esposito |first1=Michelle Marie |last2=Turku |first2=Sara |last3=Lehrfield |first3=Leora |last4=Shoman |first4=Ayat |date=2023-05-15 |title=The Impact of Human Activities on Zoonotic Infection Transmissions |journal=Animals |volume=13 |issue=10 |pages=1646 |doi=10.3390/ani13101646 |doi-access=free |issn=2076-2615 |pmc=10215220 |pmid=37238075}} Rising temperatures due to climate change create more favorable conditions for mosquitoes to expand their ranges and increase their populations. This can lead to higher rates of disease transmission in areas where these diseases were previously uncommon or nonexistent and the emergence of new diseases.{{Cite journal |last=Failloux |first=Anna-Bella |date=2019 |title=Human activities and climate change in the emergence of vector-borne diseases |url=https://comptes-rendus.academie-sciences.fr/biologies/articles/10.1016/j.crvi.2019.09.023/ |journal=Comptes Rendus. Biologies |language=fr |volume=342 |issue=7–8 |pages=269–270 |doi=10.1016/j.crvi.2019.09.023 |issn=1768-3238}}

Examples of vector-borne zoonotic diseases include:{{cite news |author=University of California - Santa Cruz |date=30 November 2012 |title=Emerging vector-borne diseases create new public health challenges |newspaper=Science Daily |location=Rockville, Maryland |url=https://www.sciencedaily.com/releases/2012/11/121130151653.htm |access-date=7 April 2014}}

• Lyme disease: Caused by the bacterium Borrelia burgdorferi, it is transmitted to humans by infected black-legged ticks, often found in wooded or grassy areas.
• Plague: Caused by the bacterium Yersinia pestis, it is primarily transmitted by fleas that infest rodents. The disease has had significant historical impacts, including the Black Death.
• West Nile virus: Transmitted by mosquitoes, it causes symptoms ranging from mild flu-like illness to severe neurological diseases, including encephalitis.

Several factors influence the incidence of vector-borne diseases, including environmental conditions, animal hosts, and the movement of people. The expansion of human settlements into previously undisturbed areas creates new habitats for vectors and animals that are potential hosts. Vector-borne zoonotic diseases are transmitted by a variety of vectors, including arthropods (mosquitoes, ticks, fleas) and rodents, with humans often acting as incidental hosts.

Humans can act as mechanical vectors for some diseases, such as Tobacco mosaic virus. TMV is a single-stranded RNA virus spread spread through physical contact. Humans physically transmit the virus with their hands or tools from plant to plant.{{Cite web |title=THE TRANSMISSION AND MANAGEMENT OF TOBACCO MOSAIC VIRUS IN A GREENHOUSE ENVIRONMENT {{!}} International Society for Horticultural Science |url=https://www.ishs.org/ishs-article/937_9 |archive-url=http://web.archive.org/web/20220630095130/https://www.ishs.org/ishs-article/937_9 |archive-date=2022-06-30 |access-date=2025-03-21 |website=www.ishs.org |language=en-US}} The concept of humans acting as a vector for TMV requires understanding the transmission dynamics and how human activity can play a role in spreading the virus among plants. Humans do not usually act as primary vectors for zoonotic diseases; however, they contribute to indirect transmission via human travel or trade aiding the spread of vector-borne diseases.

File:Gilded_Vectors_of_Disease_-_Horizontal.jpg, shows 10 different animal vectors.]]

The World Health Organization (WHO) states that control and prevention of vector-borne diseases are emphasizing "Integrated Vector Management (IVM)",{{cite web |title=Handbook for Integrated Vector Management |url=http://apps.who.int/iris/bitstream/10665/44768/1/9789241502801_eng.pdf |access-date=3 December 2015 |publisher=World Health Organization}} which is an approach that looks at the links between health and environment, optimizing benefits to both.{{efn|"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."{{cite web|title=Vector-borne disease|url=https://www.who.int/heli/risks/vectors/vector/en/|work=The Health and Environment Linkages Initiative (HELI)|publisher=World Health Organization|access-date=7 April 2014|location=Geneva, Switzerland}}}}

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.{{cite news |last=Parrish |first=Ryan |date=7 April 2014 |title=WHO focuses on vector-borne diseases for World Health Day 2014 |newspaper=Vaccine News Daily |location=Chicago, Illinois |url=http://vaccinenewsdaily.com/world_health_organization/330449-who-focuses-on-vector-borne-diseases-for-world-health-day-2014/ |access-date=7 April 2014}} It is estimated that over 80% of the world's population resides in areas under threat of at least one vector borne disease.{{Cite web |title=Vector-borne diseases |url=https://www.who.int/news-room/fact-sheets/detail/vector-borne-diseases |access-date=2023-03-31 |website=www.who.int |language=en}}{{Cite journal |last1=Qureshi |first1=Yasser M. |last2=Voloshin |first2=Vitaly |last3=Facchinelli |first3=Luca |last4=McCall |first4=Philip J. |last5=Chervova |first5=Olga |last6=Towers |first6=Cathy E. |last7=Covington |first7=James A. |last8=Towers |first8=David P. |date=2023-03-21 |title=Finding a Husband: Using Explainable AI to Define Male Mosquito Flight Differences |journal=Biology |language=en |volume=12 |issue=4 |pages=496 |doi=10.3390/biology12040496 |issn=2079-7737 |pmc=10135534 |pmid=37106697 |doi-access=free}}

• Airborne disease
• Asymptomatic carrier
• Fomite
• Globalization and disease
• Insect vectors of human pathogens
• Insect vectors of plant pathogens
• VectorBase: genomic database of invertebrate vectors of human pathogens
• List of diseases caused by insects
• Natural reservoir
• Waterborne disease
• 2007 Yap Islands Zika virus outbreak

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{{Reflist|30em}}

• [https://www.who.int/en/news-room/fact-sheets/detail/vector-borne-diseases WHO page on vector-borne diseases]

{{Commons category|Disease vectors}}

• [http://ecotippingpoints.org/our-stories/indepth/honduras-community-eradication-aedes-aegypti-dengue-zika.html Biological mosquito eradication in Monte Verde, Honduras]
• [https://www.ncbi.nlm.nih.gov/books/NBK52939/ The National Center for Biotechnology Information, Vector-borne Diseases: Understanding the Environmental, Human Health, and Ecological Connections]
• [https://www.sciencedirect.com/journal/current-research-in-parasitology-and-vector-borne-diseases Science Direct, Current Research in Parasitology and Vector-borne Diseases]
• [https://www.cdc.gov/climateandhealth/effects/vectors.htm CDC Diseases Carried by Vectors]

{{Concepts in infectious disease}}

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Category:Epidemiology

Category:Parasitology

Category:Disease transmission

Category:Infectious diseases