What is a Biological Vector?

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What Is a Biological Vector?

In biology, a vector is something that delivers a pathogen or other biological material from one place to another. The vector does not cause the disease or condition directly. It merely carries it. In physics, a vector is a line with both magnitude and direction. In both physics and biology, the definition of vector implies movement. 

When epidemiologists talk about vectors, they are usually discussing an organism that can carry a virus or bacterial infection between hosts.

For example, the mosquito is a vector for malaria. It carries the malarial parasite from person to person. Mosquitoes are also vectors for the Zika virus. Zika is an emerging infection that can cause serious problems during pregnancy. In particular, it can be damaging to the unborn child. Zika can also be sexually transmitted. 

Different species of mosquitoes can be vectors for a number of infections. Other types ofarthropods are also capable of being vectors for disease. These include sand flies, lice, fleas, and ticks. 

Did You Know: There are more than 3500 species of mosquitoes, from 41 genera. Different species are vectors for different types of infection. Not all mosquitoes are equally dangerous! However, many species within the same genus can often transmit the same infections. That is not always true. Some infections require more specific vectors than others. 

When molecular biologists talk about vectors, they mean something different.

They are usually discussing techniques for getting a slice of DNA where they need it to go. For example, they might be using tobacco mosaic virus as a vector to carry an antibody gene into a plant cell. That type of vector is used to create plants that can manufacture antibodies.

Also Known As:  Vectors are commonly conflated with carriers.

However, the two are not necessarily the same. Carrier also has several definitions. With respect to diseases, a carrier is someone who has an infection but no symptoms. A carrier can also be someone who has a genetic trait but no symptoms. 

What Are Some Examples of Biological Vectors?

  1. Sexual transmission of the Zika virus can likely be prevented with condoms or other barriers. However, prevention of Zika transmission by mosquitoes requires control of the mosquitoes as a vector. Many countries are pursuing active mosquito control to try to reduce the risk of Zika transmission. Doing so could be an effective way to reduce the long-term health damage associated with Zika infection. The emotional and financial costs of pregnant women becoming infected with the virus can be quite high. 
  2. The deer tick is a vector for Lyme disease. Research on preventing Lyme often focuses on ways to control the deer tick population. This is often seen as simpler than on other methods of prevention -- such as vaccination. Reducing risk of exposure to the vector also reduces the risk of exposure to the disease. In contrast, effective Lyme vaccines are still in development.
  3. In the spring of 2011, Nature published a study describing a new type of experimental SIV (monkey HIV) vaccine. The vaccine used CMV as a vector to elicit a long-term immune response against SIV. A gene from the SIV virus was put into CMV. Then, the CMV virus made an SIV protein. Scientists then infected monkeys with this altered CMV virus, and they used it as a vaccine. 

    What Is Integrated Vector Management?

    The World Health Organization is responsible for disease control and prevention across the globe. Part of their responsibility is tracking, and managing, vector-borne illnesses. One way that they do this is through recommending a series of techniques known as integrated vector management or IVM. The goal of IVM is to figure out the most efficient and cost-effective way to control vector-borne illness. 

    IVM is a procedure that helps communities determine what measures can be best used to control a given disease vector in a particular location. Usually, a combination of options are chosen.

    These can include anything from distribution of mosquito nets to use of pesticides to changes in sanitation practices. 

    Source:

    Hansen SG, Ford JC, Lewis MS, Ventura AB, Hughes CM, Coyne-Johnson L, Whizin N, Oswald K, Shoemaker R, Swanson T, Legasse AW, Chiuchiolo MJ, Parks CL, Axthelm MK, Nelson JA, Jarvis MA, Piatak M, Lifson JD, Picker LJ. Profound early control of highly pathogenic SIV by an effector memory T-cell vaccine. Nature. 2011 May 11. [Epub ahead of print]

    Hennessey MJ, Fischer M, Panella AJ, Kosoy OI, Laven JJ, Lanciotti RS, Staples JE. Zika Virus Disease in Travelers Returning to the United States, 2010-2014. Am J Trop Med Hyg. 2016 Jul 6;95(1):212-5. doi: 10.4269/ajtmh.16-0049.

    Kaaijk P, Luytjes W. Vaccination against Lyme disease: Are we ready for it? Hum Vaccin Immunother. 2015 Sep 4:0. [Epub ahead of print]

    Moyer MW. The growing global battle against blood-sucking ticks. Nature. 2015 Aug 27;524(7566):406-8. doi: 10.1038/524406a.

    Šmit R, Postma MJ. Lyme borreliosis: reviewing potential vaccines, clinical aspects and health economics. Expert Rev Vaccines. 2015 Sep 28:1-13.

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