The following points highlight the six major diseases caused by mosquitoes in man. The diseases are: 1. Malaria 2. Yellow Fever 3. Dengue Fever 4. Filariasis or Elephantiasis 5. Encephalitis 6. Dermatobia.
Disease # 1. Malaria:
Malaria is a deadly human disease. It is-transmitted by Anopheles’, malaria is caused by a parasitic protozoan Plasmodium which spends part of its life in man and part in the body of female Anopheles-, and the mosquito acts as a vector.
About two dozen species of Anopheles are important natural vectors of malaria in different regions of the world.
In malaria there is high recurring fever accompanied by chills and shivering, sometimes with convulsions till the teeth chatter. The patient gets violent headache and nausea followed by sweating so profuse that clothes are wet, then the temperature drops till the next attack. Often relapses occur which may prove fatal.
Disease # 2. Yellow Fever:
Yellow fever is confined to South America and Africa. It is due to a virus which causes sudden fever with severe headache and pains in the bones, the face is flushed and swollen, and the skin becomes dry. After some days severe jaundice, haemorrhage and vomiting of blood and bile occur. The mortality in yellow fever is very high.
Forest animals serve as hosts for yellow fever virus and it is transmitted by Haemogogus and several species of Aedes, such as A. aegypti, A. simpsoni, A. fluvialitis and A. albopictus; of these mosquitoes Aedes aegypti has a world-wide distribution, and with modern airplane traffic the introduction of yellow fever is an ever present menace.
Disease # 3. Dengue Fever:
Dengue or break bone fever is caused by a virus, the disease is widely distributed in warm countries. There is sudden high fever with rash on the face and intense pain in the head, eyes, muscles, and joints. Dengue is not fatal, it is transmitted by Aedes aegypti, Aedes albopictus and Culex fatigans. Dengue often breaks out abruptly in an epidemic form which spreads rapidly.
Disease # 4. Filariasis or Elephantiasis:
Filariasis is caused in man by nematodes Wuchereria bancrofti and W. malayi. The intermediate hosts are several types of mosquitoes, like Aedes, Culex, and Anopheles. The larvae of Wuchereria called microfilariae are sucked up with the blood of infected persons by mosquitoes which serve as vectors.
The microfilariae grow in mosquito and become infective. When a mosquito bites a man the larvae creep out from the proboscis on to the skin and penetrate inside, from where they go in deeper and cause inflammation of lymph glands, scrotum, arms, and legs. Filariasis may eventually cause elephantiasis but not always.
Disease # 5. Encephalitis:
Encephalitis is caused by a virus resulting in high fever, headache, drowsiness, and inflammation of the brain. It chiefly effects horses and domestic animals, but human infections also occur, though they are not common. Encephalitis is transmitted by numerous species of Aedes and Culex.
Disease # 6. Dermatobia:
Dermatobia is a disease of the skin of man and cattle. A botfly Dermatobia lays her eggs on the body of a mosquito Psorophora. When this mosquito bites, the eggs of the botfly hatch quickly on the skin of the victim, and the larvae penetrate the skin causing swellings and cutaneous myiasis. Psorophora is confined to Central and South America.