A vector in biological sciences refers either to a living organism that carries and transmits pathogens between hosts or a DNA vehicle used in molecular biology to deliver genetic material into a cell.
Vector-borne transmission and vector types
In epidemiology, a vector is an organism, often an arthropod, that conveys an infectious agent from one host to another. Biological vectors, such as mosquitoes, ticks, fleas and sand flies, support development or replication of the pathogen before transmission; mechanical vectors, such as houseflies or cockroaches, merely transport pathogens on their body surfaces without internal multiplication. Mosquitoes of the genus Anopheles transmit Plasmodium parasites that cause malaria, while Aedes mosquitoes spread dengue, Zika and yellow fever viruses. Hard ticks of the genus Ixodes serve as vectors for Lyme disease and babesiosis, and tsetse flies transmit Trypanosoma brucei, the agent of African sleeping sickness. Vector-borne diseases often involve complex life cycles with reservoir hosts and environmental factors that influence vector population dynamics. Control strategies include reducing vector habitats, using insecticides and implementing personal protective measures such as bed nets and repellents.
Vectors in molecular biology and biotechnology
In genetic engineering, a vector is a DNA molecule used to transfer foreign genes into a host cell for replication or expression. Plasmid vectors typically contain an origin of replication, a selectable marker gene and a multiple cloning site for insertion of DNA fragments. They are widely used in cloning, protein expression and recombinant vaccine production. Bacteriophage and cosmid vectors accommodate larger inserts, while bacterial artificial chromosomes and yeast artificial chromosomes allow cloning of megabase-sized DNA segments. Viral vectors derived from adenoviruses, lentiviruses and adeno-associated viruses deliver therapeutic genes into human cells in gene therapy applications. Successful vector design requires compatibility with the host system, stable maintenance of the insert and controlled expression of the transgene.
Vectors, whether biological organisms or engineered DNA molecules, facilitate the movement of pathogens or genetic material between hosts and thus play a central role in both disease transmission and modern biotechnology.
Related Terms: Arthropod vector, Plasmid, Gene therapy, Transduction, Mosquito