The Search For Better Health 2

Question 0

Identify conditions under which an organism can be described as a pathogen.

Answer 0

A pathogen is an organism or infective agent that lives on or in a living organism, and causes disease. It needs particular conditions in order to multiply and be transmitted.

There are three ways of transmission:

• Direct: person to person e.g. common cold.
• Indirect: from environment to person to person e.g. food, water, air; stomach ulcer.
• Vector: an organism which carries the pathogen e.g. mosquitoes and malaria.

Question 1

Distinguish between an infectious and non-infectious disease.

Answer 1

An infectious disease is caused by a pathogen. A pathogen may be a prion, virus, protozoa, macro-parasite, bacteria or fungi. These are also transmittable.

• Malaria: protozoa; transmitted by a vector.
• Common cold: bacteria; transmittable.
• Stomach ulcer: bacteria; transmitted by close contact or food or water.
• Genital herpes: virus; transmitted by sexual contact.
• Influenza
• Hepatitus

Non-infectious diseases cannot be transmitted (save for hereditary diseases) and are not caused by a pathogen. These may be caused by hereditary, nutritional or environmental factors.

• Down syndrome: gene mutation.
• Cystic fibrosis: gene mutation.
• Scurvy: lack of vitamin C.
• Lung cancer: malfunction of cell division.
• Beri-beri: lack of vitamin B1.
• Multiple sclerosis: gene mutation where immune system malfunctions.

Question 2

Explain why cleanliness in food, water and personal hygiene practices assist in the control of disease.

Answer 2

HYGIENE

• Personal hygiene: reduces transmission of pathogens to others and from entering body.
  e. g. washing of hands before preparing or eating food and going to the toilet; regular body washing; cleaning of teeth and hair.
• Community hygiene: ensures that pathogen transmission and accumulation is reduced. If infrastructure for this breaks down, disease can spread rapidly.
  e. g. sewerage and waste disposal systems; public toilets; sterilisation and disinfectant of equipment in hospitals, dentist clinics, restaurants etc.; effective city planning to ensure the maintenance of hygiene and reduce spread/accumulation (overcrowding a particular issue to address).

FOOD
Prevent transmission of pathogens from the environment and between people.
The bacteria ‘Salmonella’ can be spread via undercooked foods.
Strict guidelines need to be taken in the handling, storage, preparing and serving of food.
e.g. washing of hands before and during preparation of food; using different chopping boards for different foods; do not thaw food at room temperature - use a microwave or refrigerator; refrigerators 60 degrees (Salmonella killed at 71); sanitation range should be 71-100 degrees; cook food thoroughly; food reheated to 75; cover food before storage.

WATER
Reduce transmission, growth and accumulation of pathogens. In Australia, domestic water must comply with a strict standard and are tested everyday. Water treatment = pathogens killed.

Protozoans such as Cryptosporidium and and Gardia can be spread via sewerage contaminated water, so can Cholora.

Question 3

Describe the contributions of Pasteur and Koch to our understanding of infectious diseases.

Answer 3

LOUISE PASTEUR
- Pasteurisation: discovered that it was micro-organisms which caused the spoilage of alcohol and vinegar and heat could eradicate them. Lead to pasteurisation which has ensure food products such as food are pathogen free.

• The Germ Theory of Disease: disproved theory of spontaneous generation with swan-neck flask experiment.