Vector-borne pathogens and diseases (Mosquitoes)

Mosquito borne-diseases

Mosquitoes cause more human suffering than any other organism -- over one million people worldwide die from mosquito-borne diseases every year. Not only can mosquitoes carry diseases that afflict humans, they also transmit several diseases and parasites to animals. These include dog heartworm, West Nile virus (WNV) and Eastern equine encephalitis (EEE).

In addition, mosquito bites can cause severe skin irritation through an allergic reaction to the mosquito's saliva - this is what causes the red bump and itching. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases such as Lymphatic filariasis, dog heartworm, and viruses such as dengue, encephalitis and yellow fever.

These are some of the most prevalent diseases spread around the world by mosquito bites.

Diseases caused by arboviruses

Dengue Virus (DEN) is a serious arboviral disease of the Americas, Asia and Africa. It is a virus of the genus Flavivirus of family Flaviviridae. Dengue fever is caused by four different types of viruses (DENV 1, DENV 2, DENV 3, and DENV 4) Although it has a low mortality, dengue has very uncomfortable symptoms and has become more serious, both in frequency and mortality, in recent years. Stegomyia aegypti and Stalbopicta are the vectors of dengue. They bite mostly during the daytime.

Chikungunya (CHIK) is a member of the genus Alphavirus, in the family Togaviridae. Chikungunya was first described during an outbreak in southern Tanzania in 1952. The disease occurs in Africa, Europe and the Americas, Asia and the Indian subcontinent. The Chikungunya virus is most often spread to people by Stegomyia aegypti and Stegomyia albopicta mosquitoes. These are the same mosquitoes that transmit dengue virus. They bite mostly during the daytime.

Japanese encephalitis virus (JE) is the most important cause of viral encephalitis in Asia. It is a virus of the genus Flavivirus of family Flaviviridae, occurring particularly in Japan but probably widespread throughout Southeast Asia and parts of the western Pacific. Japanese encephalitis is one of a group of mosquito-transmitted viruses that can cause inflammation of the brain (encephalitis). Culex tritaeniorhynchus and Culex vishnui are the most important JE vectors.

Kunjin virus (KUN) was first isolated from Culex annulirostris collected in north Queensland in 1960. Kunjin (KUN) and West Nile (WN) viruses belong to the Japanese encephalitis (JE) antigenic complex of the genus Flavivirus in the family Flaviviridae.

Murray Valley encephalitis (MVE) is a disease caused by a virus of the genus Flavivirus of family Flaviviridae.  Most people who are infected with the virus do not feel sick. Murray Valley encephalitis is found in northern Australia and Papua New Guinea. It is transmitted by the bite of Culex annulirostris.

St. Louis encephalitis virus (SLE) is transmitted from birds to man and other mammals by infected mosquitoes (mainly some Culex species). It is a virus of the genus Flavivirus of family Flaviviridae. St. Louis encephalitis is found throughout the United States, but most often along the Gulf of Mexico, especially Florida.

West Nile virus (WNV) is a mosquito-borne zoonotic arbovirus belonging to the genus Flavivirus in the family Flaviviridae. West Nile encephalitis is a severe form of West Nile virus that occurs when the West Nile virus crosses from the blood into the brain and causes inflammation. It can cause febrile illness, inflammation of the brain or meningitis.The West Nile virus is commonly found in Europe, Africa, the Middle East, India, parts of Asia, and in Australia, the United States and Canada. The virus can infect humans, birds, mosquitoes, horses, and some other mammals. Culex mosquitoes are the most important West Nile virus vector.

Yellow fever (YF) is a viral disease found in tropical regions of Africa and the Americas. It is a virus of the genus Flavivirus of family Flaviviridae. Yellow fever principally affects humans and monkeys, and is transmitted by the bite of Stegomyia aegypti.

Wesselsbron virus (WESS) is a disease caused by a virus of the genus Flavivirus of family Flaviviridae. Wesselsbron virus was isolated in 1989 for the first time in Madagascar. It is transmitted by the bite of Aedes circumluteolus.

Zika virus (ZIKV) is a member of the genus flavivirus of family Flaviviridae. Zika virus spread outside Africa and Asia for the first time in 2007. In 2009, it was proven that Zika virus could be sexually transmitted between humans. It is related to the dengue, yellow fever, West Nile and Japanese encephalitis viruses that are transmitted by Aedini mosquitoes.

Eastern equine encephalitis virus (EEE) is a rare illness in humans, and only a few cases are reported in the United States each year. It is a virus of the genus Alphavirus of family Togaviridae. Eastern equine encephalitis is closely related to Venezuelan equine encephalitis virus and to Western equine encephalitis virus. Eastern equine encephalitis virus is transmitted by the bite of Culiseta melanura and Aedini mosquitoes.

Ross River virus (RRV) is the most common and widespread of the arboviruses that infect humans in Australia. It is a virus of the genus Alphavirus of family Togaviridae. The major vectors of Ross River virus to humans are various Culex and Aedini mosquitoes. Ross River fever cases are most commonly reported by adults. People who have been infected with the virus develop lifelong immunity.

Venezuelan equine encephalitis virus (VEE) is a common cause of encephalitis in the State of Veracruzand in the Gulf Coast region of Mexico. The virus that causes VEE is transmitted primarily by mosquitoes that bite an infected animal and then bite and feed on another animal or human.  It is a virus of the genus Alphavirus of family Togaviridae. The major vectors of Ross River virus to humans are various Culex and Aedini mosquitoes.

Western Equine Encephalitis virus (WEE) was first recognized in 1930 in a horse in California. It is found west of the Mississippi including parts of Canada and Mexico. It is a virus of the genus Alphavirus of family Togavirdae.

California encephalitis virus (CAL) was discovered in Kern County, California and causes encephalitis in humans.  It is a virus of the genus Orthobunya virus of family Bunyaviridae. Aedes triseriatus, a daytime-biting mosquito, is the most important California encephalitis virus vector.

La Crosse encephalitis virus (LAC). Most cases of LAC disease occur in the upper Midwestern and mid-Atlantic and Southeastern states. It is a virus of the genus Orthobunya virus of family Bunyaviridae. The Aedini mosquito is the most important La Crosse encephalitis vector.

Rift Valley fever (RVF) is an illness caused by a virus that is spread through mosquito bites. It is also spread by direct contact with blood, fluids, or tissues of infected animals such as cattle, buffalo, sheep, goat, and camel. It is a virus of the genus Phlebovirus of family Bunyaviridae. It was first reported in livestock by veterinary officers in Kenya’s Rift Valley in the early 1910s.

Diseases caused by parasites

Malaria is caused by the protozoan parasite Plasmodium. Human malaria is caused by four different species of Plasmodium: P. falciparum, P. malariae, P. ovale and P. vivax which are transmitted by the bites of infected anopheline mosquitoes. In the human body, the parasites multiply in the liver, and then infect red blood cells. Malaria occurs mostly in poor tropical and subtropical areas of the world. In many of the countries affected by malaria, it is a leading cause of illness and death.

Lymphatic Filariasis (elephantiasis) is caused by infection with parasites called microfilariae. There are 3 types of these thread-like filarial worms: Wuchereria bancrofti, Brugia malayi, and Brugia timori, Lymphatic filariasis can result in an altered lymphatic system and in the abnormal enlargement of body parts, causing pain, severe disability and social stigma. The most common vector is Anopheles. Culex quinquefasciatus, Aedine and Mansonia mosquitoes can transmit the infection in the Pacific and in Asia. Lymphatic filariasis largely occurs in Southeast Asia with the second largest portion of cases occurring in Africa.

Dirofilariasis is the disease caused by Dirofilaria worm infections. In dogs, one form is called "heartworm disease" and is caused by D. immitisDirofilaria immitis adult worms can cause pulmonary artery blockage in dogs, leading to an illness that can include cough, exhaustion upon exercise, fainting, coughing up blood, and severe weight loss. In humans, infection is caused most commonly by three species, D. immitisD. repens, and D. tenuis. Dirofilariasis is found throughout the world. Mosquitoes capable of transmitting Dirofilaria infection, include Anopheles, Culex, Mansonia, and Aedini mosquitoes. 

For more information:

http://www.mosquito.org/mosquito-borne-diseases

http://www.cdc.gov/ncidod/diseases/list_mosquitoborne.htm

http://emedicine.medscape.com/article/233802-overview

http://www.megacatch.com/mosquitodiseases.html

http://www.mosquitoworld.net/mosquitodiseases.php