Mosquito-borne diseases or mosquito-borne illnesses are diseases caused by bacteria, viruses or parasites transmitted by mosquitoes. Nearly 700 million people contract mosquito-borne illnesses each year, resulting in over a million deaths. Diseases transmitted by mosquitoes include malaria, dengue, West Nile virus, chikungunya, yellow fever, filariasis, tularemia, dirofilariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, Eastern equine encephalitis, Venezuelan equine encephalitis, Ross River fever, Barmah Forest fever, La Crosse encephalitis, and Zika fever, as well as newly detected Keystone virus and Rift Valley fever. A preprint by Australian research group argues that Mycobacterium ulcerans, the causative pathogen of Buruli ulcer is also transmitted by mosquitoes. There is no evidence that COVID-19 can be transmitted by mosquitoes, and it is extremely unlikely this could occur.
Types
Protozoa The female mosquito of the genus Anopheles may carry the malaria parasite. Five different species of Plasmodium cause malaria in humans: Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, Plasmodium knowlesi and Plasmodium vivax (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 the World Health Organization (WHO). The death toll increased to one million as of 2018 according to the American Mosquito Control Association.
Bacterial In January 2024, a publication by an Australian research group demonstrated significant genetic similarity between Mycobacterium ulcerans in humans and possums, compared to PCR screening of M. ulcerans from trapped Aedes notoscriptus mosquitoes, and concluded that Mycobacterium ulcerans, the causative pathogen of Buruli ulcer, is transmitted by mosquitos.
Myiasis
Botflies are known to parasitize humans or other mammalians, causing myiasis, and to use mosquitoes as intermediate vector agents to deposit eggs on a host. The human botfly Dermatobia hominis attaches its eggs to the underside of a mosquito, and when the mosquito takes a blood meal from a human or an animal, the body heat of the mammalian host induces hatching of the larvae.
Helminthiasis 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 120 million people are living with a filariasis disability.
Virus The viral diseases yellow fever, dengue fever, Zika fever and chikungunya are transmitted mostly by Aedes mosquito vectors such as Aedes aegypti and Aedes albopictus. Other viral diseases like epidemic polyarthritis, Rift Valley fever, Ross River fever, St. Louis encephalitis, West Nile fever, 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) occur in the United States where they cause 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. The ones carried solely by mosquitoes are sometimes called moboviruses (mosquito-borne viruses). West Nile virus was accidentally introduced into the US in 1999 and by 2003 had spread to almost every state with over 3,000 cases in 2006. Other species of Aedes as well as Culex and Culiseta are also involved in the transmission of disease. Myxomatosis is spread by biting insects, including mosquitoes.
Transmission A mosquito's period of feeding is often undetected; the bite only becomes apparent because of the immune reaction it provokes. When a mosquito bites a human, it injects saliva and anti-coagulants. With the initial bite to an individual, there is no reaction, but with subsequent bites, the body's immune system develops antibodies. The bites become inflamed and itchy within 24 hours. This is the usual reaction in young children. With more bites, the sensitivity of the human immune system increases, and an itchy red hive appears in minutes where the immune response has broken capillary blood vessels and fluid has collected under the skin. This type of reaction is common in older children and adults. Some adults can become desensitized to mosquitoes and have little or no reaction to their bites, while others can become hyper-sensitive with bites causing blistering, bruising, and large inflammatory reactions, a response known as skeeter syndrome. One study found Dengue virus and Zika virus altered the skin bacteria of rats in a way that caused their body odor to be more attractive to mosquitoes.
Signs and symptoms Symptoms of illness are specific to the type of viral infection and vary in severity, based on the individuals infected.
Zika virus Symptoms vary in severity, from mild unnoticeable symptoms to more common symptoms like fever, rash, headache, achy muscle and joints, and conjunctivitis. Symptoms can last several days to weeks, but death resulting from this infection is rare.
West Nile virus Most people infected with the West Nile virus usually do not develop symptoms. However, some individuals can develop cases of severe fatigue, weakness, headaches, body aches, joint and muscle pain, vomiting, diarrhea, and rash, which can last for weeks or months. More serious symptoms have a greater risk of appearing in people over 60 years of age, or those with cancer, diabetes, hypertension, and kidney disease.
Dengue fever Dengue fever is mostly characterized by high fever, headaches, joint pain, and rash. However, more severe instances can lead to hemorrhagic fever, internal bleeding, and breathing difficulty, which can be fatal.
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