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Chapter: 9th Science : World of Microbes

Vector Borne Diseases

Vector is an agent that acts as an intermediate carrier of the pathogen. Many insects and animals acts as vectors. Diseases transmitted by vectors are called vector borne diseases.

Vector Borne Diseases

Vector is an agent that acts as an intermediate carrier of the pathogen. Many insects and animals acts as vectors. Diseases transmitted by vectors are called vector borne diseases. These vectors can transfer infecting agents from an infected person to another healthy person. Some of the insect vector borne diseases are Malaria, Filaria, Chikungunya, Dengue, and the diseases which are transmitted through animals are Bird flu and Swine flu.


1. Malaria

Malaria continues to be one of the major health problems of developing countries. Malaria is caused by protozoan parasite Plasmodium. Four different species of Plasmodium namely, P.vivax, P.malariae, P.falciparum and P.ovale cause malaria. Malaria caused by Plasmodium falciparum is malignant and fatal. Approximately 300 million people around the world get infected with Malaria every year. It may be fatal to human beings, but cure is available.

It spreads through the bite of an insect vector the female Anopheles mosquito which feeds on human blood and usually lasts less than 10 days. A person affected by malaria will show symptoms of headache, nausea, muscular pain, chillness and shivering, followed by rapid rise in temperature. The fever subsides with profuse sweating. Use of Quinine drugs kills the stages of malaria parasite.


2. Chikungunya

Chikungunya, which is caused by single stranded RNA virus, is transmitted in humans by the bite of infected Aedes aegypti mosquito during the day time. It causes severe and persistent joint pain, body rashes, headache and fever. Joint pains can last for a very long time.

Incubation period of the virus is usually 2-12 days. Chillness, high fever, vomiting, nausea, headache, persistent joint pain and difficulty in walking are the common symptoms associated with this disease. The joints get inflamed and the person finds it difficult to walk. Paracetamol is given to relieve pain and reduce fever.


3. Dengue

Dengue is known as break bone fever. The name break bone fever was given because of the contortions caused due to the intense joint and muscle pain.

Dengue haemorrhagic fever is more severe form and can be life threatening or fatal.

Dengue fever and Dengue haemorrhagic fever are caused by virus. It is transmitted by Aedes aegypti mosquito that has previously bitten an infected person. Incubation period of the virus is usually 5-6 days. Onset of high fever, severe headache, muscle and joint pain (break bone fever), rash and other haemorrhagic manifestation, fall in blood platelet count are the symptoms associated with this disease. Vomiting and abdominal pain, difficulty in breathing, minute spots on the skin signifying bleeding within the skin are also associated with dengue fever. Paracetamol is given to reduce fever and body ache. Complete rest and increased intake of fluid is essential.


4. Filaria

Filariasis is a major health problem in India. This disease is caused by nematode worm Wuchereria bancrofti. The adult worms are usually found in the lymphatic system of man. It is transmitted by the bite of infected Culex mosquito.

Incubation period of filarial worm is 8-16 months and the symptoms include acute infection, fever and inflammation in lymph glands. In chronic infection the main feature is elephantiasis which affects the legs, scrotum and the arms.

The parasite is deposited at the site of mosquito bite. It passes through the punctured skin and finally reaches the lymphatic system. They appear in large number in the blood stream during night displaying nocturnal periodicity.


5. Control and prevention of vector borne diseases transmitted through mosquitoes

·           Prevention of mosquito bites by using mosquito nets, mosquito screens, mosquito repellents and ointments.

·           Elimination of breeding places by providing adequate sanitation, underground wastewater disposable system and drainage of stagnant water.

·           Collection of water in any uncovered container such as water tank, pots, flower pots, discarded tyres should be avoided.

·           Control of mosquito larvae by spraying oil on stagnated water bodies.

·           Adult mosquitoes can be killed by spraying insecticides.

·           Application of citronella oil or eucalyptus oil on the exposed skin.


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9th Science : World of Microbes : Vector Borne Diseases |

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