DISEASE CAUSING MICROORGANISMS IN HUMANS

DISEASE CAUSING MICROORGANISMS IN HUMANS

Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather. Let us study more about their harmful activities.

Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried by an animal. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.

When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air. The virus may enter the body of a healthy person while breathing and cause infection.

Then how do you prevent the spread of communicable diseases?

We should keep a handkerchief on the nose and mouth while sneezing. It is better to keep a distance from infected persons.

There are some insects and animals which act as carriers of disease- causing microbes. Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. So, it is advisable to always keep food covered. Avoid consuming uncovered items of food. Another example of a carrier is the female Anopheles mosquito (Fig. 2.8), which carries the parasite of malaria (Plasmodium). Female Aedes mosquito acts as carrier of dengue virus. How can we control the spread of malaria or dengue?

Figure 2.8: Female Anopheles mosquito

All mosquitoes breed in water. Hence, one should not let water collect anywhere, in coolers, tyres, flower pot, etc. By keeping the surroundings clean and dry we can prevent mosquitoes from breeding. Try to make a list of measures which help to avoid the spread of malaria.

Table 2.1: Some Common Human Diseases caused by Microorganisms

Some of the common diseases affecting humans, their mode of transmission and few general methods of prevention are shown in Table 2.1.

Source: This topic is taken from NCERT TEXTBOOK

DISEASE CAUSING MICROORGANISMS IN ANIMALS AND PLANTS

DISEASE CAUSING MICROORGANISMS IN ANIMALS AND PLANTS

Disease causing microorganisms in animals

Several microorganisms not only cause diseases in humans and plants, but also in other animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.

Disease causing microorganisms in plants

Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops.

See Table2.2 for some such plant diseases. They can be controlled by the use of certain chemicals which kill the microbes.

Table 2.2: Some Common Plant Diseases caused by Microorganisms

Source: This topic is taken from NCERT TEXTBOOK

FOOD POISONING

FOOD POISONING

Boojho was invited by his friend to a party and he ate a variety of foodstuff. On reaching home he started vomiting and had to be taken to a hospital. The doctor said that this condition could be due to food poisoning.

Food poisoning could be due to the consumption of food spoilt by some microorganisms. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. So, it is very important that we preserve food to prevent it from being spoilt.

Source: This topic is taken from NCERT TEXTBOOK