Wednesday, May 20, 2009

INFECTIOUS DISEASES

Infectious diseases are the diseases caused by pathogens which invade the body and grow and multiply in the tissues.

Pathogens
are parasites which cause disease. They are often referred to as germs. These are organisms that lives on or in another living organism. most pathogens are micro-organism, commonly viruses,bacteria,protozoa, and fungi.

Viruses
are so small that they cannot be seen with naked eyes or/and ordinary microscope but need the use of an electron microscope. They show only some of the property of life and can be crystallized into what appears to be a non-living form. They can only live and reproduce withing living cells, and cause a number of diseases in plants and animals. After infecting the host cell the virus uses the cell to produce new virus particles. The host cell usually get killed in the process.

Bacteria are minute organisms which are found everywhere, but it is impossible to see them without the use of microscope. Each bacterium is a single cell but lacks a definite nucleus and chlorophyll. Substances necessary for life are absorbed through the cell wall and unwanted substances excreted through the same route.

Bacteria are classified according to shape:
- Cocci are spherical
some occur singly
some in pairs- diplococci(cause gonorrhea, meningitis)
some form chains- streptococci(cause scarlet fever)
some form clusters- staphylococci(cause boils, food poisoning)

-bacilli are rod shaped- caused typhoid, tetanus, tuberculosis, diphtheria

-Vibrois are curved- caused cholera.

Protozoa are minute unicellular animals, each having a nucleus. Most are harmless to man, but few are pathogenic.
Amoeba dysentery is caused by various species of plasmodium.

Fungi are simple plants which lack chlorophyll. The group includes yeast, moulds and mushrooms. A few microscopic fungi can cause skin diseases include ringworm, athletes foot and thrush.

TRANSMISSION OF INFECTIOUS DISEASES


Infectious diseases can be spread through the following method:
1. Contact- by touching an infected person or an articles that has been contact with an infected person. These are called contagious diseases, and they include many skin diseases such as scabies, ringworm, and smallpox.

2. Droplet Infection- diseases of the respiratory tract are usually spread in this way e.g common cold and influenza. When an infected person speaks, coughs or sneezes minute droplets containing germs are released into the air which may then be inhaled by another person.

3. Contaminated Food- food can get contaminated during preparation by germs from an infected person, or flies, or dust and dirt. it may cause disease of the digestive tract e.g typhoid, and salmonella food poisoning.

4. Contaminated Water- drinking contaminated water can spread intestinal diseases. some bacteria can live for days or weeks in water. Sewage disposal and water supply should be separate to avoid contamination. Untreated water should be boiled to prevent typhoid, cholera, and amoebic dysentery.

5. Human Carrier- These are people that are infected with pathogen but not affected by them( they have immunity to it). They may not be aware that they are harboring the disease and mix freely with other people, who might contact the diseases in the process.

6. Insect Vectors- these are insects which spread diseases
- by carrying germs externally on their feet and bodies e.g houseflies carry germs from rubbish dump to food.
- by carrying the germs internally and transmitting them to the human when they pierce the skin to suck blood e.g mosquito, tsetse fly e.t.c

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Thanks for taking time out to read my articles. Please don't hesitate to leave a comment. Watch out for part II of this topic

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