Mosquito Vectors

A vector is an organism that transmits an infectious agent, such as a virus or parasite, from one host to another.  Mosquitoes typically feed on nectar and plant juices, but in some species, the female needs to obtain nutrients from a "blood meal" before she can produce eggs.  In some species, female mosquitoes feed on humans and may transmit a pathogen.  Mosquitoes can act as vectors when they bite humans.  However, of more than 3,500 mosquito species known to science, only a handful represent important disease vectors, spreading diseases to millions of people a year.

KEY MOSQUITO DISEASE VECTORS:

Important mosquito species that are known disease vectors in the Americas include:  

Aedes aegypti – Found in tropical regions worldwide, this species is a primary vector for dengue, yellow fever, and chikungunya.  It is closely associated with humans and often breeds in artificial containers such as cans, jars, bird baths, flower pots, rain barrels, or old tires, as well as septic tanks and sewage treatment plants.

Aedes albopictus – Originally from Southeast Asia, this species was first discovered in North America in 1983 and has recently been detected in many Central American countries. It is capable of transmitting many pathogens and viruses, including West Nile virus, yellow fever, St. Louis encephalitis, La Crosse encephalitis, dengue, and chikungunya. Like Aedes aegypti, this species is closely associated with humans and often breeds in artificial containers.

Culex species – Several mosquitoes in the Culex genus feed primarily on birds and may switch to feeding on humans later in their lives.  These are among the most important mosquito vectors of arboviruses in North America.  They include Culex tarsalis, Culex pipiens, Culex restuans and Culex quinquefasciatus. These species transmit West Nile virus as well as St. Louis encephalitis and Western equine encephalitis.  They breed in a variety of natural and artificial freshwater habitats.

Anopheles species – Mosquitoes of the genus Anopheles are the primary vectors of malaria worldwide. 
 

THE CHANGING STATUS OF MOSQUITO VECTORS:

Human activities have greatly increased potential development habitat for numerous mosquito species which has led to expanded ranges of many disease vectors. 

  • Human Introductions – Human movement and expanding global distribution networks, particularly cargo transit on planes and ships, has introduced mosquito species to new cities, countries, regions and continents.  Of particular concern is the recent introduction of Aedes albopictus to the Americas.
  • Consumer Products – Discarded non-biodegradable products and packaging, such as plastic, tin and tires, fill with water and create ideal breeding sites for disease vectors, such as Aedes aegypti and Aedes albopictus.
  • Climate Change – Changing patterns of temperature, rainfall and humidity affect vector distribution and abundance.  Increased temperatures enable mosquitoes to survive and breed where previously they could not. Furthermore, mosquito growth and disease transmission are often faster at higher temperatures. 
  • Transformation of Ecosystems - Human population growth and development have led to major changes in natural ecosystems, including deforestation, monoculture agriculture, nutrient loading from detergents and fertilizers, and installation of irrigation systems and dams.  Such changes have disturbed natural ecosystem functioning and increased habitat of mosquito disease vectors.
  • Poor Water and Waste Management– Inadequate garbage disposal and waste management, and poor water planning and sanitation have also contributed to the proliferation of mosquito disease vectors.  In many regions, treatment and disposal of solid and liquid waste are all but non-existent leading to contamination and eutrophication of rivers and estuaries, increasing habitat for vector mosquitoes.