Towards Better Health: How to Control Harmful Microorganisms – SS1 Biology Lesson Note (Third Term)

Harmful micro-organisms are controlled by removing them, stopping their growth or killing them. This is done with physical agents such as heat, cold, salting and drying, and with chemical agents such as antibiotics, antiseptics and disinfectants. Good sanitation, controlling vectors, protecting food and water, and a balanced diet also help to maintain good health.

Behavioural objectives

By the end of the lesson, students should be able to:

• state common methods of controlling harmful micro-organisms;
• distinguish between antiseptics and disinfectants;
• define a vector and describe how mosquitoes and houseflies are controlled;
• describe how refuse, sewage, water and food are managed to maintain good health;
• state the roles of health organisations such as WHO, UNICEF, the International Red Cross and UNESCO.

How are harmful micro-organisms controlled?

The control of harmful microbes includes removal, inhibition of growth or killing by physical agents or processes, and by chemical agents or antibiotics. Some common methods of controlling harmful micro-organisms to maintain good health include:

1. High and low temperature: Boiling or heating of food, pasteurisation of milk, sterilisation of medical instruments and freezing of food reduce the activities of microbes to the barest minimum.
2. Covering of food: This prevents vectors and pathogens in the air from coming in contact with the food.
3. Antibiotics: Antibiotics such as amoxicillin, ampicillin, penicillin and tetracycline are drugs used to kill many bacteria that cause diseases.
4. Antiseptics: Antiseptics such as Dettol, Milton, chlorine water, medicated soap and hydrogen peroxide destroy micro-organisms, while some prevent the multiplication of micro-organisms.

What is the difference between antiseptics and disinfectants?

Disinfectants are stronger antiseptics. Examples are Sanitas, Lysol and Izal. They are used to disinfect hospitals, warehouses and public buildings. Antiseptics and disinfectants have to be diluted to make them gentle or mild to the skin.

Other methods of control

5. High salinity (salting): Salt is used to preserve food. When salt is applied to food items like fresh meat or fish, the micro-organisms are destroyed. The bacterial cells are plasmolysed because water moves out of the cells of the bacteria.
6. Dehydration: When foodstuffs such as fish and meat are dried, micro-organisms cannot thrive on them. Bacteria need water to survive, so dehydration prevents their survival.
7. Sanitation: Keeping the body and the environment clean.
8. Isolation of infected persons: Persons suffering from infectious diseases such as tuberculosis and cholera must be isolated to prevent the spread of such diseases to other members of the community.
9. Balanced diet: Eating a balanced diet every day helps to promote good health and high body resistance to diseases.

What are vectors and how are they controlled?

A vector is an animal which transmits disease-causing organisms (pathogens) from the victim of that disease to another person.

Control of mosquitoes

• Draining of swamps
• Clearing of bushes around houses
• Sleeping in a room protected by a mosquito net
• Spraying swamps or rooms with insecticides
• Spraying oil on stagnant water
• Using insect repellent on the body
• Use of drugs
• Burying broken pots and cans

Control of houseflies

• Spraying with insecticides
• Destruction of breeding spots
• Use of poison baits
• Closing of pit toilets
• Covering of food
• Keeping the environment clean

How is good health maintained?

There are many ways of maintaining good health. These include refuse disposal, sewage disposal, protection of water and protection of food.

Refuse disposal

Refuse is solid waste material discharged through human activities from homes and industries into the environment. Reckless refuse dumping around dwelling places creates bad odour and provides breeding grounds for insects and rodents that spread diseases. Refuse can be disposed of in the following ways:

• Provision of dust bins in strategic locations
• Burning of refuse in incinerators
• Dumping it in isolated areas far from human habitation
• Burying refuse in sanitary landfills

Sewage disposal

Sewage is wastewater discharged from laundries, kitchens, toilets and bathrooms, for example urine and faeces. Sewage can be disposed of in the following ways:

• Pit toilets, where faeces and urine are passed into deep pits.
• Septic tanks, where water is used to flush faeces and urine into a big tank dug in the ground.
• Community treatment, where sewage from various homes is collected and treated before being discharged into the oceans or rivers.

Protection of water

People contract various diseases from drinking unclean water. Water should be protected in the following ways:

• Addition of alum to water
• Boiling of water before drinking
• Filtration of water after cooling
• Addition of chlorine to kill microscopic germs
• Storage of water in clean containers

Protection of food

The following methods of food protection are recommended:

• Keep food in refrigerators or deep freezers.
• Boil or cook raw food properly before eating.
• Inspect food meant for public consumption.
• Wash hands before and after eating food.
• Preserve food by canning.
• Keep the environment where food is prepared clean.
• Avoid exposing food to flies and other micro-organisms.

What are the roles of health organisations?

The administration of health services in Nigeria is achieved through approved organisations such as:

1. Ministry of Health
2. University Teaching Hospitals

International cooperation in health

Countries cooperate to tackle health issues. At the international level, health control is organised to prevent the spread of diseases and to provide aid to needy areas. This can be in the form of drugs, medical equipment, money and so on.

International health organisations include the World Health Organization (WHO), the United Nations Children’s Fund (UNICEF), the International Red Cross (IRC) and the United Nations Educational, Scientific and Cultural Organization (UNESCO).

World Health Organization (WHO)

This is the world’s principal agency for dealing with health and nutritional problems. It was established in 1948. Its functions are as follows:

• It provides and assists national governments, at their request, to strengthen their health services.
• It promotes and provides improved methods of training health and medical-related professional experts for member countries.
• It promotes cooperation among scientific and professional bodies for the improvement of health.
• It cooperates with other organisations in the improvement of nutrition, sanitation, housing, working conditions and other matters that relate to health.
• It helps and promotes maternal and child health care and welfare.
• It produces medical publications.
• It provides drugs and vaccines in cases of emergency.

United Nations Children’s Fund (UNICEF)

This is a body set up by the United Nations. It performs the following functions:

• It provides emergency needs for children in areas affected by diseases or famine.
• It improves the nutritional condition of undernourished children.
• It feeds and cares for disabled children.
• It undertakes immunisation programmes against children’s diseases like measles and whooping cough.
• It ensures the provision of clothing and other needs for children.

International Red Cross

This is a humanitarian organisation whose function is to serve humanity during peace and war. During war, it performs the following functions:

• Care for the injured
• Provision of emergency aid
• Negotiating for the exchange of prisoners of war
• Evacuation of refugees
• Welfare of war prisoners

United Nations Educational, Scientific and Cultural Organization (UNESCO)

UNESCO is not directly a health organisation, but it assists health services indirectly by raising the educational standards of the people in developing countries.

Evaluation

1. State four methods of controlling harmful micro-organisms.
2. What is the difference between an antiseptic and a disinfectant? Give one example of each.
3. Explain how salting preserves food.
4. List four ways of controlling houseflies.
5. State three functions of WHO.

Assignment

1. A way of providing good health in a community is
   (a) control of diseases (b) sewage disposal (c) refuse disposal (d) all of the above
2. Which of these is not a vector?
   (a) Black fly (b) Snake (c) Dog (d) Housefly
3. The process of heating liquid food at a controlled temperature, thereby enhancing its quality and destroying harmful micro-organisms, is
   (a) pasteurisation (b) boiling (c) frying (d) none of the above
4. An agent that stops the growth of fungi is called
   (a) fungistat (b) fungicide (c) germicide (d) none of the above
5. The process by which water is removed from bacteria cells, which leads to the cell being plasmolysed, is referred to as
   (a) drying (b) salting (c) dehydration (d) pasteurisation
6. Name the causative organism and vector of malaria.
7. List five symptoms of malaria.
8. Mention five ways by which mosquitoes can be controlled and state the reason for each method.