SS1 Third Term Biology Lesson Note – Towards Better Health

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WEEK 3

TOPIC: TOWARDS BETTER HEALTH

CONTENT:

• Control of harmful microorganisms
• Vectors (i) definition (ii) ways of controlling vectors
• Student’s health: maintenance of good health

Sub – Topic 1: TOWARDS BETTER HEALTH: CONTROL OF HARMFUL MICRO-ORGANISMS

Better health can be achieved basically by controlling disease-causing micro-organisms and their animal vectors and also by improving health facilities.

Harmful microorganisms can be controlled by;

(1) Use of high temperature e.g. sterilization by boiling, autoclaving or heating of food, water and other products to kill micro-organisms.

(2) Use of drugs / antibiotics e.g. chloroquine kills plasmodium parasites.

(3) Use of antiseptics which kill or inhibit the growth of pathogenic micro-organisms.

(4) By immunization or vaccination against diseases such as measles, tuberculosis, polio, etc.

(5) Covering of food and water always to prevent contact with vectors.

(6) Destruction of vectors such as mosquitoes, flies, rats, etc.

(7) Use of disinfectants e.g. Lysol, carbonic acid, etc.

(8) Use of salt; this inhibits the growth of microbial cells and prevents their multiplication. Salt can be used to preserve food and wash cuts and wounds to prevent infection.

(9) Dehydration inhibits the growth of microbes; food can be preserved by drying. Drying in the sun can be used to kill micro-organisms in bedding blankets and clothes.

(10) Promoting health education.

Sub –Topic 2: VECTORS

Non-living agents that carry micro-organisms from one place to another include air, water and food.

Living agents that carry micro-organisms from place to place are animals. These animals that carry pathogenic (disease causing) micro-organisms are known as vectors.

Examples of vectors are cockroaches, fleas, mosquitoes, tsetse-flies, black flies, house flies, bed-bugs, ticks, rats, dogs, cats, etc. Vectors may transmit micro-organisms from place to place or person to person either mechanically or biologically.

(a) Mechanical Method: The vectors carry pathogens on various parts of their bodies e.g. legs, wings, mouthparts, hairs, etc. The pathogens do not grow or multiply on the body of the vectors. Pathogens carried in this way include Salmonella typhi, Vibro cholerae and Entamoeba histolytica.

(b) Biological Method: The vector in this case becomes infected with the pathogen when it feeds on the body fluid of an infected person or animal. The pathogen develops and multiplies in the body of the vector which then infects a healthy person when it goes to feed. Thus part of the pathogen’s life cycle takes place in the body of the vector. Examples of such vectors and the pathogen they carry are;

(i) Anopheles mosquito (female) carries plasmodium (protozoan) that causes malaria.

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