Disease is the name given to any condition that prevents an organism from functioning effectively. For example, diseases include influenza, short-sightedness, asthma and cancer.
TYPES OF DISEASE
Diseases are classified as Hereditary or Congenital Diseases (an organism has these at birth) and Acquired Diseases (an organism has these only after birth).
- Hereditary or Congenital Diseases
Examples include Haemophilia (a bleeding disease where the blood does not clot properly because it lacks a protein necessary to clot), and Sickle-Cell Anaemia (a disease in which a person has deformed red blood cells that cannot carry sufficient oxygen for the body and causes them to clump together causing blockages in blood vessels).
There are 5 types of acquired disease that people may develop during their lives.
- Infectious Diseases - caused by a living organism (e.g. virus, bacteria, fungus, protozoan, worm)
- Diet and Deficiency Diseases - caused by too much or too little of certain nutrients in our food ( e.g. scurvy, rickets)
- Cancers - caused by rapid and uncontrolled growth of cells into tumours (e.g. lung cancer, skin cancer or melanoma)
- Occupational Diseases - acquired during incidents in the working environment (e.g. pesticide poisoning on a farm)
- Heart Diseases - caused by a malfunctioning of the heart and blood vessels, due to smoking, stress and poor diet (e.g. angina)
INFECTIOUS OR CONTAGIOUS DISEASE
- Causative Organism - virus (e.g. influenza, measles), bacteria ( e.g. tetanus, typhoid fever), fungus (e.g. tinea), protozoan (e.g. malaria), worm (e.g. tapeworm)
- 3 Shapes of Bacteria - coccus (round), bacillus (rod-shaped), spirillus (spiral)
- Signs and Symptoms - e.g. fever, pain, diarrhoea
- Mode of Spread - droplet (e.g. influenza), direct contact (e.g. tinea), sexual contact (e.g. AIDS), food and water contaminated from faeces (e.g.cholera), vector such as a mosquito (e.g. malaria)
- Preventative Treatment - e.g. immunisation or vaccination, mosquito repellent
- Treatment after contracting disease - Antibiotics are not effective against viral infections. Other medications may be available.
FIGHTING INFECTIOUS DISEASES
- Defences that are not part of the Immune System include an intact skin, tears to wash away dust, mucus and cilia (nose hairs) to trap dust in the respiratory tract, hydrochloric acid in the stomach to kill bacteria in food, and blood clotting by blood platelets.
- Immune System Defences are many white blood cells (leukocytes) and antibodies. There are two main types of white blood cells - those which digest foreign particles (phagocytes), and those that make chemicals such as antibodies and antitoxins to neutralise foreign particles (lymphocytes).
- Antibiotics - Antibiotics work by preventing the growth of micro-organisms. They have little or no effect on viruses.
- Immunisation may be active (the body fights infection by producing its own antibodies), or passive (the antibodies are either injected or fed in breast milk). A person who has been exposed to a disease may build up his/her own antibodies to fight that same disease the next time they come in contact with it.
- Immunisation by injecting or orally giving the dead or altered micro-organism may be done for short- or long-term prevention of the disease.
- Pregnant or breast-feeding mothers may give antibodies to the baby through blood or milk.