notes prepared by subhankar Karmakar
HARMFUL MICROORGANISMS:
Those microorganisms which cause diseases are harmful to us and called pathogens. Pathogens can be bacteria, viruses, protozoa, fungi etc.
Communicable diseases:
Those microbial diseases which can spread from an infected person to a healthy person through air, water, food or physical contact, etc are called communicable diseases.
Some of the examples of communicable diseases are: Common cold, Cholera, Chicken pox, Tuberculosis (TB), Malaria and AIDS.
Different ways by which communicable diseases can occur and spread:
Any communicable diseases can occur and spread in the following ways:
1. By breathing of air containing microorganisms,
2. By taking infected food or water,
3. Through insect bites,
4. By sharing infected injection needles,
5. By physical contact with an infected person.
Prevention of communicable diseases:
Methods for preventing the occurrence and spreading of communicable diseases are as follows: -
1. A person suffering from common cold or influenza should always cover his mouth and nose with a handkerchief while sneezing, so that microorganisms are not being released into the air. We must keep a social distancing too.
2. We should keep our food covered to protect it from getting infected by flies. You should also drink clean and safe water.
3. We should use mosquito nets to protect ourselves from mosquito bites
4. Disposable syringes and needles should we use for injection.
5. A person infected by a communicable disease should be quarantined.
6. We should follow proper vaccination at proper time.
Vectors or carriers of disease causing microorganisms:
The insects or other animals which transmit disease-causing microorganisms to humans without itself suffering from them are called vectors or carriers.
The most common Carriers of disease causing microorganisms are:
1. Housefly and
2. Mosquito
A. Housefly as the vectors of diseases:
Some of the dangerous diseases spread by housefly are: cholera, tuberculosis (TB), typhoid and diarrhoea.
Prevention of diseases spread by housefly:
The spreading of diseases by houseflies can be prevented in the following ways:
1. Household garbage should be put in garbage bin which should be kept covered. This will prevent the house flies from breeding because they will not be able to lay their eggs on garbage.
2. The food should always be kept covered so that flies cannot sit on it.
3. We should avoid eating uncovered food items from the roadside stalls.
4. The flies should be killed by using insecticide spray.
5. We should take proper vaccination as some of the diseases spread by housefly can be prevented by vaccination.
B. Mosquitoes as the vectors of diseases:
Mosquito spread diseases by transmitting disease causing microorganisms through its bites.
The most common diseases spread by mosquitoes are malaria and dengue fever.
Prevention of diseases spread by mosquitoes:
The spreading of diseases by mosquitoes can be prevented in the following ways:
1. As the mosquitoes breed in stagnant water, we should avoid any pools of stagnant water around the houses and our surroundings should be clean and dry.
2. The windows and doors of the house should have fine iron wire mesh so that mosquitoes cannot enter our house.
3. Insecticides should be spread in houses periodically to kill mosquitoes.
4. Oil should be sprayed on the surface of water in dirty water drains to kill the larvae of mosquitoes.
5. Mosquito net should be used over beds while sleeping to prevent mosquito bites.
Some of the common diseases caused by bacteria:
Tuberculosis, Cholera, Typhoid etc.
Some of the common diseases caused by virus:
Measles, Chicken pox, Polio, Hepatitis B, Dengue.
Disease causing microorganisms in animals:
Some of the example of diseases caused in animals by the microorganisms are: foot and mouth disease, anthrax, aspergillosis.
1. Foot and mouth disease of animals like cattle is caused by a virus.
2. Anthrax is a dangerous disease of animals like cattle which is caused by a bacterium, known as bacillus anthracis.
3. Aspergillosis is a disease of animals like poultry birds which is caused by fungus.
Disease causing microorganisms in plants:
Several microorganisms cause diseases in plants like Wheat, Rice, Potato, Orange, Apple and others.
Some of the common plant diseases caused by microorganisms are: rust of wheat, citrus canker and yellow vein mosaic of bhindi.
Rust of wheat is caused by fungi.
Citrus canker is caused by bacteria.
Yellow vein mosaic of bhindi is caused by virus.
Food poisoning:
The disease caused due to the presence of a large number of microorganisms like bacteria and fungi in the food or due to the presence of toxic substances in food formed by the action of microorganisms is called food poisoning.
The major symptoms of food poisoning are: vomiting, diarrhoea, pain in abdomen, headache and fever.
The most common microorganisms which cause food poisoning are salmonella bacteria, clostridium botulinum bacteria and aspergillus fungus.
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