Biology and Geology

ESO 3

YEAR 2015 -16

Unit 2

DISEASES:CAUSES, TRANSMISSION AND CONTROL

ILLNESSES

An illness is any physical or mental alteration

that causes an organism to malfunction.

Types of Diseases

NON TRANSMISSIBLES DISEASES

They may be genetic, nutritional, degenerative,

etc.. They aren´t produced by pathogenic

agents.

TRANSMISSIBLES DISEASES OR

INFECTIOUS DISEASES

It can be passed from one person to another.

They are caused by bacteria, viruses, fungi,

protozoa and metazoa.

Bacteria

Good bacteria or friendly bacteria are those

that are in the digestive system and help it to

work and inhibit the growth of bad bacteria.

BACTERIAL DISEASES

They are caused by different pathogenic

bacteria.

Salmonella Streptococcus

Bacterial Diseases

The ill-effects of a bacterial disease are

caused mainly by poisonous products

produced either by the bacteria or by the

cells which they invade.

Bacterial poisons are called toxins.

Symptons: raised temperature, headache,

tiredness and weakness and sometimes

diarrhoea and vomiting.

Examples of Bacterial Diseases

Scarlet fever

Tetanus, botulism

Tonsillitis, boils

Tuberculosis, cholera, whooping cough

Food poisoning, gonorrohea or syphilis

WE CAN USE DRUGS (ANTIBIOTICS) AGAINST BACTERIA

Viral Diseases

The common cold virus

The flu

AIDS

Bacterial Viruses

Virus Reproduction

Viruses

They can reproduce only inside other cells,

and so all viruses are parasitic. Viruses don´t

produce toxins.

The harm they cause is probably the result of

the destruction of the cells they invade.

We cannot use antibiotics or other drugs

against viruses.

You can get immunity but unfortunately many

viruses can change by mutation.

Examples of Virus Diseases

The common cold

Flu

AIDS

Herpes, mumps, measles, chickenpox,

rubella or hepatitis.

Fungal parasites

Athlete´s foot

Ringworm

Candida

Fungi deseases

Several species of fungus give rise to the

various forms of this disease. The fungus

attacks the epidermis and produces a patch

of inflammed tissue.

The region of the body affected will depend

on the species of fungus.

All forms of the disease are very contagious.

They are spread by contact with an infected

person or their personal property.

Examples of Fungal Diseases

Candida

Tinea

- Ringworm

- Tinea of the crutch

- Tinea of the scalp

- Athlete´s foot

Protozoan Parasites

There are relatively few protozoa which

parasitize humans, but those that do cause

serious diseases.

Two of these are malaria and amoebic

dysentery.

malaria

vector protozoo

Metazoan parasites

They can be worms or arthropodes. Lice (louse)

Diseases transmission mechanisms

A) Direct transmission

The pathogenic agent is transmitted from

infected people to healthy people.

Through saliva or mucus expelled when

coughing or sneezing.

Direct contact.

Diseases Transmission Mechanisms

B) Indirect transmission: They may also involve

a vector.

The main vector are: contaminated water,

contaminated food and through an

arthropod´s bite.

Airborne, droplet or aerosol infection

If the droplets contain viruses or bacteria,

they may cause disease when they are eaten

with food or inhaled.

When the droplets evaporates bacteria often

die but viruses remain infectious floating in

the air for a long time.

Virus: cold, flu, measles, chikenpot and some

bacterias as Streptococci (Sore throats)

Contamination of Water

If disease bacteria gets into water supplies

used for drinking, hundreds of people can

become infected. Example: cholera or

typhoid.

Some of these bacteria will pass out with

faeces. If the faeces get into streams or

rivers they be carried into reservoirs of water

used for drinking.

To prevent this from happening faeces must

be made harmless and drinking water

purified.