Biology Year 12 MODULE 7: Infectious Disease

What is an Epidemic?

Disease spreads and infects rapidly in specific area

• Seasonal Flu

• Cholera

What is an Endemic?

Disease is consistently prevalent in specific area (usually low)

• Malaria in Africa

• Chickenpox in children

What is a Pandemic?

Disease spreads and infects rapidly not limited to specific area (global)

• Spanish Flu

• Coronavirus

Definition of Disease

A health condition which adversely impacts function or structure of an organism

What is a genetic disease?

Disease caused by changes/mutations to DNA, affecting genes or chromosomes

• Down Syndrome

• Cystic Fibrosis

What is an Environmental Disease?

Disease caused by environmental factors

• Mesothelioma (asbestos)

• Melanoma

What is a Nutritional Disease?

Disease caused by poor/inadequate nutritional factors

• Scurvy

• Type 2 diabetes

Outline the effects of type 2 diabetes

Causes body to become resistant to insulin, cells can’t use it properly

Insulin builds up in blood, causes Hyperglycemia

What is Infectious Disease?

Diseases caused by a pathogen transmitted between organisms

What is Prion Disease?

Misfolded brain proteins become infectious, clog nerve cells and block messages

Outline Bacteria

Microscopic single-celled living organisms, prokaryotic, replicate via binary fission —> 1-5μm

• Salmonella

• Gonnorhoea

Outline Virus

Non-cellular, intracellular parasites, Replicate inside host cell, —>

20-300nm

• Rhinovirus

• Influenza

• HIV

Outline Fungi

Eukaryotic organisms, cellular, chemoheterotrophic (relying onother organisms to provide food and energy), reproduce sexually and asexually

• Ringworm

• Athletes foot

What is Direct Transmission?

Transmission via direct contact

• Touching

• Kissing

• Sexual intercourse

• Contact with nasal or oral secretions

What is Indirect Transmission?

Spread of germs via indirect contact (umbrella term)

→ Vehicle transmission

→ Vector transmission

→ Fomites

What is Vehicle Transmission? (indirect)

Transmission via contaminated food or water

• Contaminated water

• Contaminated meat/food supply

• Mad Cow Disease

• Cholera

What is Vector Transmission? (indirect)

Transmission via insects and animals carrying disease

• Mosquitoes

• Toxoplasmosis

• Flies carrying feces

What is an incubator?

Specialised warming chamber to provide stable condition for microorganism growth

What is a Protozoa?

single-celled, eukaryotic organisms, replicate sexually and asexually, motile, —> 10-100μm

• Intestinal Giardia (diarrheoa)

What is an agar plate

Sterile petri dish to culture and isolate microorganisms

What is Phytopthora Dieback?

Soil-borne mold pathogen, causing plants to rot

Signs/Symptoms of Phytopthora Dieback

Wilting of leaves

Stunted growth

Darkened roots

Branch rotting

how is Phytopthora transmitted?

Movement of contaminated soil, mud + water.

Prevention/Treatment of Phytopthora Dieback

Cleaning tools and shoes

Phosphorous acid

Improved drainage

Phytopthora dieback favourable conditions

Moist soil

Poor drainage

What is a CRAAP test?

Currency

Recency

Authority

Accuracy

Purpose

VAR of Secondary Source

Validity: Relevant, trusted, up to date, expert

Accuracy: Information is factually correct, methods are outlined

Reliability: Consistent across other credible sources

What is a dependent variable?

The factor being measured/examined

What is an independent variable?

Variable that is changed to assess impact on dependent variable

What is a controlled variable?

Factors controlled to prevent influencing of results

VAR of Method

Validity: Is it testing what’s meant to be tested

Accuracy: Are values close to accepted value (water boils at 100*C)

Reliability: Multiple trials result in similar results

What did Louis Pasteur discover

• Swan-necked flask: Boiling microorganisms kills them

• Germ theory: Infectious Diseases are caused by pathogens (microscopic)

• Disproved spontaneous generation

Robert Koch Postulates

Proved germ theory

Identified causes of Anthrax, Tuberculosis, cholera

What are public health outcomes

• Changes in incidence, prevalence, mortality

• Re-admission rates, quality of life, patient experience

What is the First Line of Defence?

Basic, innate, non-specific defence to stop pathogens entering organs + body

Parts of the First Line of Defence

Physical defence: —> Skin, nasal hair, eyelashes, mucous membranes, urination

Chemical defence: Low pH (skin, gastric acid, vagina)

How does the skin prevent entry of pathogens

• Largest organ in body

• Releases Sebum (making skin unsuitable for microbial growth)

• Keratinised (waterproof)

How does mucus/mucous membranes prevent entry of pathogens?

• Sticky, traps microorganisms

• Covers tender skin (mucus coats cuts/wounds)

• Houses antimicrobial enzymes

What is a macroscopic organism?

multicellular organism, visible to naked eye, replicates via larvae/eggs

>1mm

• Tapeworm