Vector-borne diseases

A vector is a living organism that transmits an infectious agent from an infected animal to a human or another animal. Vectors are frequently arthropods, such as mosquitoes, ticks, flies, fleas and lice.    
Vectors can transmit infectious diseases either actively or passively:

  • Biological vectors, such as mosquitoes and ticks may carry pathogens that can multiply within their bodies and be delivered to new hosts, usually by biting.
  • Mechanical vectors, such as flies can pick up infectious agents on the outside of their bodies and transmit them through physical contact.

Diseases transmitted by vectors are called vector-borne diseases. Many vector-borne diseases are zoonotic diseases, i.e. diseases that can be transmitted directly or indirectly between animals and humans. These include for example Lyme disease, tick-borne encephalitis, West Nile virus, Leishmaniosis and Crimean-Congo haemorrhagic fever.
Many vector-borne diseases are considered as emerging infectious diseases in the European Union:

  • a disease that appears in a population for the first time, or
  • that may have existed previously but is rapidly increasing in incidence or geographic range.

Some vectors are able to move considerable distances. This may affect the transmission ranges of vector-borne zoonotic diseases. Vectors can be introduced to new geographic areas for example by:

  • travel of humans and international trade;
  • animal movement, for instance of livestock;
  • migratory birds;
  • changing agricultural practices;
  • or the wind.

Other factors may play a role in their establishment and persistence in new areas, including climatic conditions.

EFSA's role

EFSA provides independent scientific advice and scientific assistance on human health and animal health-related aspects of vector-borne zoonotic diseases. The role of EFSA’s Panel on Animal Health and Welfare in this area is to provide scientific advice to risk managers on the animal health-related aspects of vector-borne diseases. EFSA monitors and analyses the situation on zoonoses, zoonotic micro-organisms, antimicrobial resistance, microbiological contaminants and food-borne outbreaks across Europe.

EFSA works in close cooperation with European Centre for Disease Prevention and Control (ECDC) in this area by sharing information on present and future projects on vectors and vector-borne zoonotic diseases. This cooperation will lead to the development of a common database on vectors and vector-borne diseases.

EFSA’s work on vector-borne zoonotic diseases has among others included an overview of the geographic distribution of ticks and tick-borne pathogens in Europe and the Mediterranean basin, and a specific assessment on the role of ticks as vectors of Crimean-Congo haemorrhagic fever virus.

Based on data collected by the EU Member States, EFSA produces in cooperation with ECDC annual European Union Summary Reports on vector-borne zoonoses in animals and food-borne outbreaks caused by these micro-organisms.

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Last updated: 29 July 2014