Vector

Definition

An organism that acquires a pathogen or parasite from one host and transmits it to another, serving as an essential biological bridge in the life cycle of the disease agent. In medical and veterinary entomology, vectors are typically blood-feeding arthropods—such as mosquitoes, ticks, fleas, or kissing bugs—that ingest pathogens during feeding, allow replication or development of the agent within their bodies, and then infect new hosts during subsequent blood meals. The term distinguishes mechanical vectors (which passively carry pathogens on body surfaces) from biological vectors (in which the pathogen undergoes obligatory development or multiplication).

Etymology

Latin vector, 'carrier' or 'conveyor,' from vehere, 'to carry.'

Example

Anopheles gambiae mosquitoes are the principal biological vectors of Plasmodium falciparum malaria in sub-Saharan Africa: the protozoan parasite undergoes sexual reproduction in the mosquito midgut, migrates to the salivary glands, and is injected into a new human host during the next blood-feeding event.

Synonyms

• disease vector
• carrier

Related Terms

• host
• reservoir
• pathogen
• parasite
• Mechanical vector
• Biological vector
• Vector competence
• Vector capacity
• zoonosis
• ectoparasite
• endoparasite

Usage Notes

In entomology, 'vector' almost always implies biological transmission with pathogen development inside the vector; contrast with 'carrier' in epidemiology, which may include asymptomatic infected hosts that do not transmit. Vector competence (ability to become infected and transmit) and vector capacity (overall transmission potential in a population) are distinct quantitative measures. The term should not be applied to organisms that merely contaminate surfaces without internal pathogen development.