Mosquitoes are known to carry many infectious diseases from several different classes of microorganisms, including viruses and parasites. Mosquito-borne illnesses include malaria, West Nile virus, elephantiasis, dengue fever, yellow fever etc. These infections are normally rare to certain geographic areas.
The female mosquito of the genus carries (see Plasmodium). Worldwide, malaria is a leading cause of premature mortality, particularly in children under the age of five, with an estimated 207 million cases and more than half a million deaths in 2012, according to the World Malaria Report 2013 published by WHO.
The human botfly (Dermatobia hominis) attacks and uses a mosquito during mid-flight to deliver its eggs and transfer it to a person; the eggs are in the underside of the mosquito vector which is stuck with a special glue. When the mosquito takes a blood meal from its human host, the body heat of the mammalian host melts the glue and the eggs hatch into larvae which feed on human flesh and blood. Other botfly use the same strategy as the human botfly.
Some species of mosquito can carry the filariasis worm, a parasite that causes a disfiguring condition (often referred to as elephantiasis) characterized by a great swelling of several parts of the body; worldwide, around 40 million people are living with a filariasis disability.
Other viral diseases like epidemic polyarthritis, Rift Valley fever, Ross River fever, St. Louis encephalitis, West Nile virus (WNV), Japanese encephalitis, La Crosse encephalitis and several other encephalitic diseases are carried by several different mosquitoes. Eastern equine encephalitis (EEE) and Western equine encephalitis (WEE) occurs in the United States where it causes disease in humans, horses, and some bird species. Because of the high mortality rate, EEE and WEE are regarded as two of the most serious mosquito-borne diseases in the United States. Symptoms range from mild flu-like illness to encephalitis, coma and death.
Viruses carried by arthropods such as mosquitoes or ticks are known collectively as arboviruses. West Nile virus was accidentally introduced into the United States in 1999 and by 2003 had spread to almost every state with over 3,000 cases in 2006.
Some viruses tend to be specific to a species and/or genus of mosquito. The following mosquito species transmit disease to humans/animals:
Mosquitos carrying such arboviruses stay healthy because their immune systems recognizes the virions as foreign particles and "chop off" the virus's genetic coding, rendering it inert. Human infection with a mosquito-borne virus occurs when a female mosquito bites someone while its immune system is still in the process of destroying the virus's harmful coding. It is not completely known how mosquitoes handle eukaryotic parasites to carry them without being harmed. Data has shown that the malaria parasite Plasmodium falciparum alters the mosquito vector's feeding behavior by increasing frequency of biting in infected mosquitoes, thus increasing the chance of transmitting the parasite.
When a mosquito bites, she also injects saliva and anti-coagulants into the blood which may also contain disease-causing viruses or other parasites. This cycle can be interrupted by killing the mosquitoes, isolating infected people from all mosquitoes while they are infectious or vaccinating the exposed population. All three techniques have been used, often in combination, to control mosquito transmitted diseases. Window screens, introduced in the 1880s, were called "the most humane contribution the 19th century made to the preservation of sanity and good temper."
Mosquitoes are estimated to transmit disease to more than 700 million people annually in Africa, South America, Central America, Mexico and much of Asia with millions of resulting deaths. In Europe, Russia, Greenland, Canada, the United States, Australia, New Zealand, Japan and other temperate and developed countries, mosquito bites are now mostly an irritating nuisance but still cause some deaths each year.
Historically, before mosquito transmitted diseases were brought under control, they caused tens of thousands of deaths in these countries and hundreds of thousands of infections. Mosquitoes were shown to be the method by which yellow fever and malaria were transmitted from person to person by Walter Reed, William C. Gorgas and associates in the U.S. Army Medical Corps first in Cuba and then around the Panama Canal in the early 1900s. Since then other diseases have been shown to be transmitted the same way.
Mosquitoes are a perfect example of one of the many organisms that can host diseases. Of the known 14,000 infectious microorganisms, 600 are shared between animals and humans. Mosquitoes are known to carry many infectious diseases from several different classes of microorganisms, including viruses and parasites. Mosquito-borne illnesses include malaria, West Nile virus, elephantiasis, dengue fever, yellow fever etc. These infections are normally rare to certain geographic areas. For instance dengue hemorrhagic fever is a viral, mosquito borne illness usually regarded only as a risk in the tropics. However, cases of dengue fever have been popping up in the U.S. along the Texas-Mexican border where it has never been seen before. In 2015 it was also reported that, due to climate change, mosquitoes had started to spread historically rare diseases to Europe - malaria to Greece, West Nile virus to eastern Europe and chikungunya to Italy and France.
- Mosquito-borne diseases, infectious disease information, NCID, CDC
- Susannah F Locke (1 December 2008). "Bug vs Bug: How do mosquitoes survive deadly viruses unscathed?".
- Koella, J.C.; Sorensen; Anderson (7 May 1998). "The malaria parasite, Plasmodium falciparum, increases the frequency of multiple feeding of its mosquito vector, Anopheles gambiae". Proceedings of the Royal Society B 265 (1398): 763–768. doi:10.1098/rspb.1998.0358. Retrieved 2 May 2013.
- "History of and Reasons for Mosquito Control in New Jersey Chemigation works in combination with existing irrigation systems: The Fertibug case studies show control relevance with a system that will deliver pesticides that modify the growth cycle of mosquitoes in both the larvae and adult stages. System attaches directly to a sprinkler system and uses the high pressure and vast reach of the irrigation system’s water distribution means to evenly and continuously disperse liquid insecticides in minute quantities―think parts per million PPM. Immediate effect will be noticed with a diminished mosquito population.". Archived from the original on 2 November 2000. line feed character in
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- "Mosquitoes and Mosquito Repellents: A Clinician's Guide"; by Mark S. Fradin: Annals of Internal Medicine, 1 June 1998. 128:931-940. Retrieved 10 July 2006.
- The American Plague, by Molly Caldwell Crosby, p. 12, Berkley Books, New York, 2005, ISBN 0-425-21202-5
- The Path Between the Seas: The Creation of the Panama Canal 1870-1914, by David McCullough, 1977, Simon and Schuster, ISBN 0-671-24409-4
- The American Plague, by Molly Caldwell Crosby, pp. 100-202, Berkley Books, New York, 2005, ISBN 0-425-21202-5
- (23 March 2015) Mosquitoes 'could bring exotic diseases to UK' BBC News, Health, Retrieved 23 March 2015