A vector is a living organism that carries and can transmit an infectious agent, or pathogen, from one host organism, such as a human or animal, to another. Vector-borne diseases represent 17% of all infectious diseases, are responsible for more than one million deaths each year, and current estimates indicate that at least half of the world’s population is at risk from them.
This process commonly occurs when a bloodsucking organism, such as a mosquito, ingests the pathogen whilst taking a blood meal from an infected human or animal, and later injects the pathogen into another host when taking its next blood meal.
Many organisms serve as vectors of pathogens important to human health, of which mosquitoes are one of the most well-known. Examples of vectors and the major pathogens they transmit include:
| Vector | Disease |
|---|---|
| Anopheles mosquitoes | Malaria (caused by Plasmodium spp.) |
| Aedes mosquitoes (including Aedes aegypti) | Yellow fever, dengue, Chikungunya, and Zika (all caused by viruses) |
| Culex mosquitoes | West Nile (caused by a virus), Lymphatic filariasis (caused by a parasitic worm) |
| Ticks | Lyme disease (caused by Borrelia burgdorferi), Tick-borne encephalitis (caused by a virus) |
| Sandflies | Leishmaniasis (caused by Leishmania spp.) |
| Triatomine (kissing) bugs | Chagas disease (caused by Trypanosoma cruzi) |
| Tsetse flies | Human African Trypanosomiansis or sleeping sickness (caused by Trypanosoma brucei) |
| Fleas | Plague (caused by Yersinia pestis) |
| Blackflies | Onchcerciasis or river blindness (caused by Onchocerca volvulus) |
| Disease | Million DALYs |
|---|---|
| Mosquito-borne infections | |
| Malaria | 46.5 |
| Lymphatic filariasis | 5.8 |
| Dengue | 0.62 |
| Japanese encephalitis | 0.71 |
| Yellow fever | No data |
| Others | |
| Onchocerciasis | 0.48 |
| Leishmaniasis | 2.1 |
| African trypanosomiasis | 1.5 |
| Chagas | 0.67 |