Disease vector

Agent that carries and transmits pathogens

A mosquito shortly 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, including malaria.

In epidemiology, a disease vector is any living[1] agent that carries and transmits an infectious pathogen such as a parasite or microbe, to another living organism.[2][3] Agents regarded as vectors are mostly blood-sucking (hematophagous) arthropods such as mosquitoes. The first major discovery of a disease vector came from Ronald Ross in 1897, who discovered the malaria pathogen when he dissected the stomach tissue of a mosquito.[4][5]

## Arthropods

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The deer tick, 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 and ticks feed on blood, the pathogen enters the blood stream of the host. This can happen in different ways.[6][7]

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 (mosquito saliva contains a cocktail of proteins that facilitate blood feeding by anaesthetizing the bite site, preventing blood clotting and modulating the host immune system among other things[8]). Therefore, the parasites are transmitted directly into the host's blood stream. Pool feeders such as the sand fly, tsetse and black fly, vectors for pathogens causing leishmaniasis, African trypanosomiasis and onchocerciasis respectively, will chew a well in the host's skin, forming a small pool of blood from which they feed. Leishmania and trypanosome parasites then infect the host through the saliva of the sandfly or tsetse, respectively. Onchocerca force their own way out of the insect's head into the pool of blood.[9][10]

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.[11][12][13][14]

There are several species of Thrips that act as vectors for over 20 viruses, especially Tospoviruses, and cause all sorts of plant diseases.[15][16]

## Plants and fungi

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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.[17]

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.[18]

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.[19] [17]

## Mammals

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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.[20]

## Vector-borne zoonotic disease and human activity

[edit]

This figure shows how the Flavivirus 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.[a] 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.[21] 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.[22] 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.[23]

Examples of vector-borne zoonotic diseases include:[24]

* 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.[24] 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.[25] 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.

## Control and prevention

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Public health agencies educate people about many different disease vectors. This artwork, at the London School of Hygiene and Tropical Medicine, 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)",[26] which is an approach that looks at the links between health and environment, optimizing benefits to both.[b][27]

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.[28] It is estimated that over 80% of the world's population resides in areas under threat of at least one vector borne disease.[1][29]

## See also

[edit]

* 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

## 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."[21]
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."[27]

## References

[edit]

1. ^ a b "Vector-borne diseases". WHO.
2. ^ "Vector". WordNet Search 3.1. Princeton University. Retrieved 7 April 2014.
3. ^ Porta, Miquel, ed. (2014). "Vector-Borne Infection". A Dictionary of Epidemiology. doi:10.1093/acref/9780199976720.001.0001. ISBN 978-0-19-997672-0.
4. ^ Muacevic, Alexander (2024-08-02). "The Legacy of Sir Ronald Ross: From Malaria Research to Multifaceted Achievements". Cureus. 16 (8): e65999. doi:10.7759/cureus.65999. PMC 11366213. PMID 39221355.
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. Archived from the original on May 19, 2017. Retrieved 2020-10-23.
6. ^ "Classification of Animal Parasites". plpnemweb.ucdavis.edu. Archived from the original on 2017-10-06. Retrieved 2016-02-25.
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. PMID 10589879.
8. ^ "[SEMINAR BLOG] THE BATTLE FOR BLOOD - HOW MOSQUITO SALIVARY PROTEINS FACILITATE BLOOD FEEDING". Department of Entomology. Retrieved 2025-05-29.
9. ^ "8.20D: Arthropods as Vectors". 23 June 2017.
10. ^ "PEOI Foundations of Public Health".
11. ^ "CDC - Chagas Disease - Detailed Fact Sheet". 11 April 2022.[dead link]
12. ^ "Coronavirus disease 2019 (COVID-19) - Symptoms and causes". Mayo Clinic.
13. ^ "CDC - Chagas Disease - General Information". 13 April 2022.
14. ^ "Chagas disease". WHO.
15. ^ Sarwar, Muhammad (2020). "Insects as transport devices of plant viruses". Applied Plant Virology. pp. 381–402\. doi:10.1016/B978-0-12-818654-1.00027-X. ISBN 978-0-12-818654-1.
16. ^ Jayasinghe, Wikum H.; Wagh, Sopan Ganpatrao; Bhor, Sachin Ashok; Akhter, Md Shamim (2023). "Plant RNA virus vector interactions in epidemiology of plant viral diseases". Plant RNA Viruses. pp. 329–348\. doi:10.1016/B978-0-323-95339-9.00023-5. ISBN 978-0-323-95339-9.
17. ^ a b R. S. Mehrotra (2013). Fundamentals of Plant Pathology. Tata McGraw-Hill Education. pp. 342–. ISBN 978-1-259-02955-4.
18. ^ Peter W. Price (1980). Evolutionary Biology of Parasites. Princeton University Press. pp. 61–. ISBN 0-691-08257-X.
19. ^ Haynes, Alan R; Coile, Nancy C; Schubert, Timothy S (1996). Comparison of Two Parasitic Vines: Dodder (Cuscuta) and Woe Vine (Cassytha) (PDF) (Report). Botany Circular No. 30. Florida Department of Agriculture and Consumer Services, the Division of Plant Industry.
20. ^ "Raccoons and public health". The Humane Society of the United States. Retrieved 2022-04-01.
21. ^ a b Purlain, Ted (5 December 2012). "Lancet addresses emerging infectious vector-borne diseases". Vaccine News Daily. Chicago, Illinois. Retrieved 7 April 2014.
22. ^ Esposito, Michelle Marie; Turku, Sara; Lehrfield, Leora; Shoman, Ayat (15 May 2023). "The Impact of Human Activities on Zoonotic Infection Transmissions". Animals. 13 (10): 1646. doi:10.3390/ani13101646. PMC 10215220. PMID 37238075.
23. ^ Failloux, Anna-Bella (September 2019). "Human activities and climate change in the emergence of vector-borne diseases". Comptes Rendus. Biologies. 342 (7–8): 269–270\. doi:10.1016/j.crvi.2019.09.023.7–8&rft.pages=269-270&rft.date=2019-09&rft_id=info:doi/10.1016/j.crvi.2019.09.023&rft.aulast=Failloux&rft.aufirst=Anna-Bella&rfr_id=info:sid/en.wikipedia.org:Disease+vector" class="Z3988">
24. ^ a b "Emerging vector-borne diseases create new public health challenges". ScienceDaily (Press release). University of California - Santa Cruz. 30 November 2012.
25. ^ "THE TRANSMISSION AND MANAGEMENT OF TOBACCO MOSAIC VIRUS IN A GREENHOUSE ENVIRONMENT | International Society for Horticultural Science". www.ishs.org. Archived from the original on 2022-06-30. Retrieved 2025-03-21.
26. ^ Handbook for integrated vector management. World Health Organization. 2012. hdl:10665/44768. ISBN 978-92-4-150280-1.[page needed]
27. ^ a b "Vector-borne disease". The Health and Environment Linkages Initiative (HELI). Geneva, Switzerland: World Health Organization. Retrieved 7 April 2014.
28. ^ Parrish, Ryan (7 April 2014). "WHO focuses on vector-borne diseases for World Health Day 2014". Vaccine News Daily. Chicago, Illinois. Retrieved 7 April 2014.
29. ^ Qureshi, Yasser M.; Voloshin, Vitaly; Facchinelli, Luca; McCall, Philip J.; Chervova, Olga; Towers, Cathy E.; Covington, James A.; Towers, David P. (24 March 2023). "Finding a Husband: Using Explainable AI to Define Male Mosquito Flight Differences". Biology. 12 (4): 496. doi:10.3390/biology12040496. PMC 10135534. PMID 37106697.

## External links

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* WHO page on vector-borne diseases

Wikimedia Commons has media related to Disease vectors.

* Biological mosquito eradication in Monte Verde, Honduras
* The National Center for Biotechnology Information, Vector-borne Diseases: Understanding the Environmental, Human Health, and Ecological Connections
* CDC Diseases Carried by Vectors
* UK's One Health Vector-Borne Diseases Hub

* v
* t
* e

Concepts in infectious disease (Outline)

Determinants|

| Agent|

* Biofilm
* Germ theory of disease
* Infectivity
* Infectious dose
* Pathogenicity
* Attack rate
* Quorum sensing
* Virulence
* Endotoxin
* Exotoxin
* Case fatality rate
* factors
* Antimicrobial resistance
* Drug resistance
* Horizontal gene transfer
* Multidrug-resistant bacteria
* Host tropism

|

Host|

* Burn
* Comorbidity
* Diabetes
* Host–pathogen interaction
* Immune response
* Immunodeficiency
* Immunosuppression
* Microbiome health
* Opportunistic infection
* Risk of infection
* Susceptible individual
* Age
* Gender
* Nutrition status
* Vaccination status
* Genetic predisposition
* Behavioral/lifestyle factors
* Smoking
* Pregnancy
* Stress levels

Environment|

* Access to water, sanitation, and hygiene
* Air quality
* Biodiversity loss
* Climate change
* Climate zones
* El Niño
* Tropical diseases
* Commerce
* Deforestation
* Ecology
* Humidity
* Injection drug use
* Natural disaster
* Flood
* Poultry and livestock
* Poverty
* Travel
* Urbanization
* Vector control
* War and conflict

Transmission|

| Basic
concepts|

* Asymptomatic carrier
* Chain of infection
* Fomite
* Host
* Incubation period
* Index case
* Infectious period
* Latent period
* Natural reservoir
* Opportunistic infection
* Silent/Subclinical infection
* Superinfection
* Super-spreader
* Viral load
* Window period

|

Modes|

| Endogenous|

* Endogenous overgrowth
* Normal flora overgrowth
* Endogenous reactivation
* Microbial translocation
* Endogenous seeding
* Biofilm formation

|

Exogenous|

| Cross-species|

* Spillover infection
* Vector
* Zoonosis
* Reverse zoonosis

|

Human-to-human
/Cross-infection|

* Contagious disease
* Source
* Nosocomial/Hospital
* Iatrogenic/Medical care
* Generational difference
* Vertical/Congenital
* Prenatal
* Perinatal
* Neonatal
* Horizontal
* Breakthrough infection

Environment-
to-human|

* Sapronosis

Routes|

| Respiratory|

* Air
* Bioaerosol
* Aerosol-generating procedure
* Dental aerosol
* Respiratory droplet

|

Linked to
Vascular system|

* Blood-borne disease
* Percutaneous inoculation
* Injection site
* Intravenous line
* Insect bite
* Animal bite
* Surgical intervention
* Postoperative wound
* Surgical site infection
* Vector-borne
* Mosquito
* Tick

Gastrointestinal|

* Food
* Contamination
* Breastmilk
* Water
* Feces

Cutaneous|

* Burn
* Fomite
* Soil
* Open wound

Genitourinary|

* Sex

Trans-placental|

* Prenatal

Cervico-vaginal|

* Perinatal

Other|

* Ocular (Eye) mucosal membrane

Modelling|

* Agent-based model
* Animal disease model
* Attack rate
* Basic reproduction number
* Compartmental models in epidemiology
* Critical community size
* Force of infection
* Herd immunity
* Infection rate
* Machine learning
* Multiplicity of infection
* Serial interval
* WAIFW matrix

Occurrence
in population|

* Cluster
* Endemic
* Epidemic
* Curve
* Farr's laws
* Holoendemic
* Hyperendemic
* Incidence
* Inequality
* Mesoendemic
* Outbreak
* Pandemic
* Prevalence
* Seasonality
* Geographic distribution
* Sporadic
* Syndemic
* Twindemic

Anatomical
location|

* Respiratory
* Ear-Nose-Throat/Upper respiratory tract
* Chest/Lower respiratory tract
* Gastrointestinal
* Intestinal
* Genitourinary
* Nervous system
* Skin
* Soft tissue
* Bone
* Joint
* Cardiovascular
* Systemic/Generalized
* Blood
* Tooth
* Mouth
* Fetus
* Eye

Prevention
and Control
measures|

| Pharmaceutical|

* Antibiotic
* prophylactic
* Antifungal
* Anthelmintic
* Ascaricide
* Antimicrobial
* Antimicrobial stewardship
* Antiseptic
* Antiviral
* Asepsis
* Combination
* Drug safety
* Immunization
* Immunotherapy
* Monoclonal antibody therapy
* Inoculation
* Phage therapy
* Pre-exposure prophylaxis
* Post-exposure prophylaxis
* Repurposed drugs
* Vaccination
* efficacy/effectiveness
* booster
* resistance
* Vaccine-preventable disease
* Ring vaccination

|

Non-
pharmaceutical|

* Contact tracing
* Cordon sanitaire
* Disease surveillance
* Disinfection
* Flattening the curve
* Hygiene
* Food hygiene
* Hand washing
* Gloves
* Isolation
* Barrier nursing
* Lockdown
* Notification
* list
* Protective sequestration
* Public health
* Community health services
* Health communication
* Health education
* Outbreak response
* Quarantine
* Respiratory source control
* N95 respirator
* Surgical mask
* PPE
* Safe sex
* Sanitation
* Screening
* Social distancing
* Sterilization
* Transmission-based precautions
* Travel restrictions
* Universal precautions
* Vector control
* Wastewater surveillance
* Zoning

Emerging
infections|

* Antigenic drift
* Antigenic shift
* Antimicrobial resistance surveillance
* EARS-Net
* Biosecurity
* CRISPR
* Disease X
* Emergent virus
* Evolutionary epidemiology
* Genetic epidemiology
* Global Health Initiatives
* Microbial phylogenetics
* One Health Model
* Genomic reassortment
* Re-emerging disease
* Reverse zoonosis
* Selection pressure
* Synthetic biology
* Viral phylodynamics

Other|

* Discovery
* Eradication
* Economics of Infectious Diseases
* Infectious disease (medical specialty)
* Infectious disease informatics
* Microbial bioterrorism
* Pandemic prevention
* Tropical disease
* Tropical medicine

Authority control databases

National|

* Germany
* Czech Republic

Other|

* Yale LUX

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