An Overview of Harmful Micro-Organisms

One of the interesting Biology Topics is the study of animal behavior and how it is influenced by genetics and the environment.

Carriers of Disease Causing Micro-Organisms

Micro-organisms can be harmful in many ways. For example, some of the micro-organisms cause diseases in human beings, other animals and plants. Those micro-organisms which cause diseases are called pathogens. Thus, pathogens are disease-causing micro-organisms. Pathogens can be bacteria, viruses, protozoa or fungi, etc.

Micro-organisms cause diseases such as tuberculosis (TB), tetanus, diphtheria, whooping cough, cholera, typhoid, AIDS, food poisoning, malaria, smallpox and chickenpox, etc. Some micro-organisms spoil food, clothing and leather objects. We will now study some of the harmful activities of micro-organisms in detail.

Disease-Causing Micro-Organisms In Humans

Disease-causing micro-organisms (or pathogens) enter our body through the air we breathe, the water we drink, or the food we eat. The disease-causing micro-organisms can also get transmitted by direct contact with an infected person or carried through an insect (or other animal). When pathogens (such as bacteria, viruses, protozoa, fungi, etc.) enter our body, they cause diseases.

A person who has disease-causing micro-organisms (or microbes) in his body is said to be an ‘infected person’. 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.

In communicable diseases, the disease-causing germs (or infection) get transmitted from a human being, an animal or the environment to another human being. Some of the examples of communicable diseases are : Common cold, Cholera, Chickenpox, Tuberculosis (TB), Malaria, and AIDS.

For example, the disease called ‘common cold’ spreads by breathing air containing micro-organisms. This happens as follows : The disease ‘common cold’ is caused by a virus. A person suffering from common cold is infected with ‘common cold virus’. When the person suffering from common cold sneezes, fine droplets of moisture carrying thousands of common cold viruses are spread in the air around him (or her) (see Figure).

When a healthy person breathes in this contaminated air containing common cold virus, the virus enters his body and he also gets common cold’ disease. The communicable diseases can occur and spread in the following ways:

1. by breathing of air containing micro-organisms,
2. by taking infected food or water,
3. through insect bites (such as mosquito bites),
4. by sharing infected injection needles, and
5. by physical contact with an infected person (or by using articles of an infected person such as towel, clothes, bed, utensils, etc.).

For example, the common cold disease spreads by breathing air containing micro-organisms ; the disease called cholera spreads by taking infected food or water ; the disease called malaria spreads through insect bites (mosquito bites); and the disease called AIDS spreads by sharing infected injection needles or through physical contact (sexual contact) with an infected person.

Prevention of Communicable Diseases

Some of the methods for preventing the occurrence and spreading of communicable diseases are given below:
(i) A person suffering from common cold should always cover his mouth and nose with a handkerchief while sneezing, so that micro-organisms do not get into the air. We should also keep a safe distance from a person having common cold.

(ii) We should keep our food covered to protect it from getting infected by flies. We should also drink clean and safe water.

(iii) We should protect ourselves from mosquito bites by using mosquito nets over our beds while sleeping, by putting fine wire mesh on doors and windows, or by using mosquito repellant creams and devices.

(iv) We should make sure that only disposable syringes and needles are used for giving us injections.

(v) We should avoid physical contact with an infected person, and not use his towel, clothes or bed. The towel, clothes and utensils used by an infected person should be washed and cleaned separately with soap and hot water.

(vi) Some of the diseases can be prevented by vaccination at proper time.

Carriers of Disease-Causing Micro-Organisms

There are some insects in our environment which transfer disease-causing microbes into our body (either by contaminating our food or by biting into our body), and spread diseases. The two most common insects which carry disease-causing micro-organisms (microbes or pathogens) are the housefly and mosquito.

The insect (or other animal) which transmits disease-causing micro-organisms to humans (without itself suffering from them) is called a ‘carrier’. We can now say that there are some insects which act as carriers of disease-causing micro-organisms. The two most common carriers of disease-causing micro-organisms (or microbes) are :

1. Housefly, and
2. Mosquito.

We will now describe the role of houseflies and mosquitoes in spreading diseases. Please note that houseflies breed and feed in filthy places (insanitary places) which contain a lot of disease-causing micro-organisms (microbes or pathogens). And mosquitoes breed in pools of stagnant water.

The Role of Housefly in Spreading Diseases

The houseflies lay eggs on garbage dumps. So, they breed on filth and refuse (kachra). The houseflies feed on garbage, animal excreta, dead organic matter and exposed human food (uncovered human food). The body and legs of housefly bear a lot of fine hair (see Figure ).

When the housefly sits on a garbage heap, human excreta or other filth and refuse, then millions of disease-causing micro-organisms (like bacteria) present in them stick to the hairy legs and other body parts of the housefly [see Figure (a)]. And when this housefly now sits on our uncovered food, then the micro-organisms sticking to the hair on its legs and other body parts are transferred to food [see Figure (b)].

In this way our food gets contaminated with disease-causing micro-organisms. When this contaminated food is consumed by a person, then the disease causing micro-organisms enter into his body and cause various diseases. The person gets sick. Thus, the housefly carries disease-causing micro-organisms (or germs) on the hair of its legs and other body parts.

It is the habit of housefly of sitting on garbage and human food alternately which is responsible for the transmission of micro-organisms to our body and causing diseases. Some of the dangerous diseases spread by houseflies are : Cholera, Tuberculosis (TB), Typhoid and Diarrhoea.

Prevention of Diseases Spread by Houseflies

The spreading of diseases by houseflies can be prevented in the following ways :

1. We should not leave household garbage here and there. The garbage should be put in the garbage bins which should be kept covered. This will prevent the houseflies 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 road-side stalls.
4. The flies should be killed by using insecticide spray and baits.
5. Some of the diseases spread by houseflies can be prevented by vaccination.