Vector (disease)
Encyclopedia
In epidemiology
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...

, a vector is any agent (person, animal or microorganism
Microorganism
A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

) that carries and transmits an infectious pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...

 into another living organism.
Vectors are vehicles by which infections are transmitted from one host to another. Most commonly known vectors consist of arthropods, domestic animals or mammals that assist in transmitting parasitic organisms to humans or other mammals. A vector is not only required for part of the parasite's developmental cycle, but it also transmits the parasite directly to subsequent hosts
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...

.

Arthropods as vector

Arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

s form a major group of disease vectors with mosquitoes, flies, sand flies, lice, fleas, ticks and mites transmitting a huge number of diseases. Many such vectors are haematophagous, which feed on blood at some or all stages of their lives. When the insects blood feed, the parasite enters the blood stream of the host. This can happen in different ways.

The Anopheles
Anopheles
Anopheles is a genus of mosquito. There are approximately 460 recognized species: while over 100 can transmit human malaria, only 30–40 commonly transmit parasites of the genus Plasmodium, which cause malaria in humans in endemic areas...

mosquito, a vector for Malaria
Malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

, Filariasis
Filariasis
Filariasis is a parasitic disease and is considered an infectious tropical disease, that is caused by thread-like nematodes belonging to the superfamily Filarioidea, also known as "filariae"....

 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
Phlebotominae
Members of the subfamily Phlebotominae are known outside of the United States by the name sand fly. This subfamily includes numerous genera of blood-feeding flies, including the primary vectors of leishmaniasis, bartonellosis and pappataci fever...

 and black fly
Black fly
A black fly is any member of the family Simuliidae of the Culicomorpha infraorder. They are related to the Ceratopogonidae, Chironomidae, and Thaumaleidae. There are over 1,800 known species of black flies . Most species belong to the immense genus Simulium...

, vectors for Leishmaniasis
Leishmaniasis
Leishmaniasis is a disease caused by protozoan parasites that belong to the genus Leishmania and is transmitted by the bite of certain species of sand fly...

 and Onchocerciasis
Onchocerciasis
Onchocerciasis , also known as river blindness and Robles' disease, is a parasitic disease caused by infection by Onchocerca volvulus, a nematode . Onchocerciasis is the world's second-leading infectious cause of blindness. It is not the nematode, but its endosymbiont, Wolbachia pipientis, that...

 respectively, will chew a well in the host's skin, forming a small pool of blood from which they feed. Leishmania
Leishmania
Leishmania is a genus of Trypanosomatid protozoa, and is the parasite responsible for the disease leishmaniasis. It is spread through sandflies of the genus Phlebotomus in the Old World, and of the genus Lutzomyia in the New World. Their primary hosts are vertebrates; Leishmania commonly infects...

parasites then infect the host through the saliva of the sand fly. Onchocerca
Onchocerca
Onchocerca is a genus of roundworm. It contains one human parasite - Onchocerca volvulus - which is responsible for the neglected disease Onchocerciasis, also known as "River Blindness" because the infected humans tend to live near rivers where host black flies live...

 force their own way out of the insect's head into the pool of blood.

Triatomine bugs
Triatominae
The members of Triatominae , a subfamily of Reduviidae, are also known as conenose bugs, kissing bugs, assassin bugs or triatomines. Most of the 130 or more species of this subfamily are haematophagous, i.e. feed on vertebrate blood; a very few species feed on other invertebrates...

 are responsible for the transmission of a trypanosome
Trypanosoma
Trypanosoma is a genus of kinetoplastids , a monophyletic group of unicellular parasitic flagellate protozoa. The name is derived from the Greek trypano and soma because of their corkscrew-like motion. All trypanosomes are heteroxenous and are transmitted via a vector...

, Trypanosoma cruzi
Trypanosoma cruzi
Trypanosoma cruzi is a species of parasitic euglenoid trypanosomes. This species causes the trypanosomiasis diseases in humans and animals in America...

, 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.

Examples of vectors

  • Aedes
    Aedes
    Aedes is a genus of mosquito originally found in tropical and subtropical zones, but now found on all continents excluding Antarctica. Some species have been spread by human activity. Aedes albopictus, a most invasive species was recently spread to the New World, including the U.S., by the used...

    mosquitoes are vectors of avian malaria
    Avian malaria
    Avian malaria is a parasitic disease of birds.-Etiology:Avian malaria is most notably caused by Plasmodium relictum, a protist that infects birds in tropical regions...

    , dengue fever
    Dengue fever
    Dengue fever , also known as breakbone fever, is an infectious tropical disease caused by the dengue virus. Symptoms include fever, headache, muscle and joint pains, and a characteristic skin rash that is similar to measles...

    , yellow fever
    Yellow fever
    Yellow fever is an acute viral hemorrhagic disease. The virus is a 40 to 50 nm enveloped RNA virus with positive sense of the Flaviviridae family....

     and chikungunya
    Chikungunya
    Chikungunya virus is an insect-borne virus, of the genus Alphavirus, that is transmitted to humans by virus-carrying Aedes mosquitoes. There have been recent breakouts of CHIKV associated with severe illness...

    .
  • Aphid
    Aphid
    Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...

    s are the vectors of many viral diseases in plants.
  • Bats
    Bats
    A bat is a flying mammal in the Chiroptera order.Bats may also refer to:-Films:*Bats , starring Lou Diamond Phillips and Bob Gunton*Bats: Human Harvest -Groups:...

     which represent about 20% of all known mammalian species act as both a natural reservoir
    Natural reservoir
    Natural reservoir or nidus, refers to the long-term host of the pathogen of an infectious disease. It is often the case that hosts do not get the disease carried by the pathogen or it is carried as a subclinical infection and so asymptomatic and non-lethal...

    s for viruses such as the Hendra virus (HeV) and the SARS like coronaviruses
    Coronavirus
    Coronaviruses are species in the genera of virus belonging to the subfamily Coronavirinae in the family Coronaviridae. Coronaviruses are enveloped viruses with a positive-sense single-stranded RNA genome and a helical symmetry. The genomic size of coronaviruses ranges from approximately 16 to 31...

    and in many cases as a vector for various viruses such as the lyssaviruses
    Lyssavirus
    Lyssavirus is a genus of viruses belonging to the family Rhabdoviridae, in the order Mononegavirales. This group of RNA viruses includes the Rabies virus traditionally associated with the disease.-Structure:Viruses typically have either helical or cubic symmetry...

     including the rabies virus
    Rabies virus
    The rabies virus is neurotropic virus that causes fatal disease in human and animals. Rabies transmission can occur through the saliva of animals....

    .
  • Cyclopoid copepod
    Cyclopoida
    Cyclopoida is an order of small crustaceans from the subclass Copepoda. Like many other copepods, members of Cyclopoida are small, planktonic animals living both in the sea and in freshwater habitats. They are capable of rapid movement...

    s; a number of species transmit the nematode Dracunculus medinensis
    Dracunculus medinensis
    Dracunculus medinensis is a nematode that causes dracunculiasis.Dracunculiasis, also known as Guinea worm disease, is caused by the large female nematode, Dracunculus medinensis, which is among the longest nematodes infecting humans. The adult female is primarily larger than the adult male. The...

    .
  • Domestic cats are the primary host species for Toxoplasma gondii
    Toxoplasma gondii
    Toxoplasma gondii is a species of parasitic protozoa in the genus Toxoplasma. The definitive host of T. gondii is the cat, but the parasite can be carried by many warm-blooded animals . Toxoplasmosis, the disease of which T...

    a species of parasitic protozoa
    Protozoa
    Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...

     which causes Toxoplasmosis
    Toxoplasmosis
    Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. The parasite infects most genera of warm-blooded animals, including humans, but the primary host is the felid family. Animals are infected by eating infected meat, by ingestion of feces of a cat that has itself...

    .Approximately 30% of the human population is infected with Toxoplasmosis.
  • Flea
    Flea
    Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...

    s such as the human flea, Pulex irritans
    Human flea
    The human flea, Pulex irritans, is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. It is one of six species in the genus Pulex; the other five are all confined to the Nearctic and Neotropical regions...

    and the Oriental rat flea, Xenopsylla cheopis, transmit bubonic plague
    Bubonic plague
    Plague is a deadly infectious disease that is caused by the enterobacteria Yersinia pestis, named after the French-Swiss bacteriologist Alexandre Yersin. Primarily carried by rodents and spread to humans via fleas, the disease is notorious throughout history, due to the unrivaled scale of death...

    , murine typhus
    Murine typhus
    Murine typhus is a form of typhus transmitted by fleas , usually on rats. Murine typhus is an under-recognized entity, as it is often confused with viral illnesses...

     and tapeworms
    Cestoda
    This article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...

    .
  • Glassy-winged sharpshooter
    Glassy-winged sharpshooter
    The glassy-winged sharpshooter is a large leafhopper insect from the family Cicadellidae, similar to other species of sharpshooter.-Description:These sharpshooters are about in length...

     transmits the Xylella fastidiosa
    Xylella fastidiosa
    Xylella fastidiosa, a bacterium in the class Gammaproteobacteria, is an important plant pathogen that causes phoney peach disease in the southern United States, oleander leaf scorch, and Pierce's disease, and citrus variegated chlorosis disease in Brazil.-Pierce's disease:Pierce's disease was...

    bacterium among plants, resulting in diseases of grapes, almonds, and many other cultivated plants.
  • Mosquito
    Mosquito
    Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

    es of the Anopheles
    Anopheles
    Anopheles is a genus of mosquito. There are approximately 460 recognized species: while over 100 can transmit human malaria, only 30–40 commonly transmit parasites of the genus Plasmodium, which cause malaria in humans in endemic areas...

    genus transmit human Malaria
    Malaria
    Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

     and Elephantiasis
    Elephantiasis
    Elephantiasis is a disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs and male genitals. In some cases the disease can cause certain body parts, such as the scrotum, to swell to the size of a softball or basketball. It is caused by...

    .
  • Phlebotomine
    Phlebotominae
    Members of the subfamily Phlebotominae are known outside of the United States by the name sand fly. This subfamily includes numerous genera of blood-feeding flies, including the primary vectors of leishmaniasis, bartonellosis and pappataci fever...

     sand flies transmit leishmaniasis
    Leishmaniasis
    Leishmaniasis is a disease caused by protozoan parasites that belong to the genus Leishmania and is transmitted by the bite of certain species of sand fly...

    , bartonellosis
    Bartonellosis
    Bartonellosis is an infectious disease produced by bacteria of the genus Bartonella. Bartonella species cause diseases such as Carrión´s disease, trench fever, and cat scratch disease, and other recognized diseases, such as bacillary angiomatosis, peliosis hepatis, chronic bacteremia, endocarditis,...

    , sandfly fever
    Sandfly fever
    Sandfly fever can refer to:* Visceral leishmaniasis, or kala-azar* Pappataci fever/ Papatasi fever, an acute febrile arboviral infection...

     and pappataci fever
    Pappataci fever
    Pappataci fever is a vector-borne febrile arboviral infection caused by three serotypes of Phlebovirus. Occurs in subtropical regions of the Eastern Hemisphere...

    .
  • Tick
    Tick
    Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...

    s of the genus Ixodes
    Ixodes
    Ixodes is a genus of hard-bodied ticks . It includes important disease vectors of animals and humans . Some ticks in this genus may transmit the pathogenic bacterium Borrelia burgdorferi responsible for causing Lyme disease...

    are vectors of Lyme disease
    Lyme disease
    Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...

     and babesiosis
    Babesiosis
    Babesiosis is a malaria-like parasitic disease caused by infection with Babesia, a genus of protozoal piroplasms. After trypanosomes, Babesia are thought to be the second most common blood parasites of mammals and they can have a major impact on health of domestic animals in areas without severe...

    .and along with lice transmit various members of the bacterial genus Rickettsia
    Rickettsia
    Rickettsia is a genus of non-motile, Gram-negative, non-sporeforming, highly pleomorphic bacteria that can present as cocci , rods or thread-like . Being obligate intracellular parasites, the Rickettsia survival depends on entry, growth, and replication within the cytoplasm of eukaryotic host cells...

    .
  • Triatomine bugs
    Triatominae
    The members of Triatominae , a subfamily of Reduviidae, are also known as conenose bugs, kissing bugs, assassin bugs or triatomines. Most of the 130 or more species of this subfamily are haematophagous, i.e. feed on vertebrate blood; a very few species feed on other invertebrates...

     such as Rhodnius prolixus
    Rhodnius prolixus
    Rhodnius prolixus is the second most important triatomine vector of the Chagas parasite due to its efficient adaptation to the human domicile in northern South America, where sylvatic populations also exist, and in Central America where it is exclusively domestic...

    are vectors of Chagas disease
    Chagas disease
    Chagas disease is a tropical parasitic disease caused by the flagellate protozoan Trypanosoma cruzi. T. cruzi is commonly transmitted to humans and other mammals by an insect vector, the blood-sucking insects of the subfamily Triatominae most commonly species belonging to the Triatoma, Rhodnius,...

    .
  • Tsetse flies
    Tsetse fly
    Tsetse , sometimes spelled tzetze and also known as tik-tik flies, are large biting flies that inhabit much of mid-continental Africa between the Sahara and the Kalahari deserts. They live by feeding on the blood of vertebrate animals and are the primary biological vectors of trypanosomes, which...

     Several genera
    Genera
    Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

     are vectors of human African trypanosomiasis also known as "African sleeping sickness".
  • Mabelocking birds  have been known to transmit many airborne human diseases diseases including Streptococcus
    Streptococcus
    Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...

     .

See also

  • Globalization and disease
    Globalization and disease
    Globalization, the flow of information, goods, capital and people across political and geographic boundaries, has helped to spread some of the deadliest infectious diseases known to humans. The spread of diseases across wide geographic scales has increased through history...

  • VectorBase: genomic database of invertebrate vectors of human pathogens
    VectorBase
    is one of the five Bioinformatics Resource Centers funded by the National Institutes of Allergy and Infectious Diseases, NIAID a component of the National Institutes of Health , which is an agency of the United States Department of Health and Human Services...

  • Water-borne disease
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