B5: Communicable diseases

Health

A state of physical + mental well-being

Disease

Conditions that can cause ill health

How are diseases classed?

• Communicable (infectious)

• Non-communicable

Communicable disease

• Can spread from 1 organism to another

• Spread by pathogens

What are communicable diseases spread by?

Pathogens

Non-communicable disease

Can’t spread from 1 organism to another

What can ill health be caused by?

1. Communicable + non-communicable disease

2. Poor diet

3. High stress levels

4. Life situations

   • Eg working w harmful chemicals

How can diseases interact?

1. Defects in IS → individual more likely to suffer from infectious diseases

2. Viruses living in cells trigger cancers

3. Immune reactions initially caused by a pathogen can trigger allergies (skin rashes + asthma)

4. Severe physical ill health can lead to depression + other mental illness

Tuberculosis (TB)

• Communicable lung disease

• Can be fatal

How does having HIV increase the risk of contracting TB?

People with defective immune system (eg w HIV), more likely to suffer from infectious disease (TB)

Human papilloma virus (HPV)

• V common

• Harmless in most people

What disease can HPV cause in some people?

Cervical cancer

• As HPV infects cells of the cervix

How can a disease be triggered by the immune system (eg allergies)?

• Body infected w pathogen

• IS fights off pathogen

• Person left with allergy

Viruses living in cells can trigger…

Changes that lead to cancers

How can a mental illness be triggered by a physical illness?

• Person w arthritis- hard to move

• Makes them feel isolated + depresed

Pathogen

Microorganisms that cause infectious disease

Pathogen examples

1. Bacteria

2. Virus

3. Protist

4. Fungi

How do bacteria make us ill?

1. Once inside human body, B reproduce v quickly

2. B then release toxins

3. Toxins- damage tissues + make us feel ill

Under ideal conditions how often can bacteria divide?

Every 20 mins

Toxins

Harmful chemicals

What do bacteria release that make us feel ill?

Toxins

What do toxins do?

Damage tissues + make us feel ill

What do viruses need to reproduce?

Inside host cell

• Can’t reproduce by themselves

How do viruses make us feel ill?

1. Virus invades + reproduces host cell (v damging for HC)

2. When virus leaves cell → causes cell to burst open + die

What happens when a virus leaves a cell?

Causes cell to burst open + die

How are pathogens spread?

1. Air, eg in water droplets

2. Water

3. Direct contact betw individuals

Factors affecting physical + mental health

1. Diet

2. Stress

3. Life situations

How can diseases interact? general

1. 1 disease can increase the risk of contracting another

2. 1 disease can be the cause of another

3. Disease can be triggered by the immune system

4. Mental illness can be triggered by a physical illness

What can bacteria + viruses both do inside the body?

Reproduce rapidly

What do viruses do?

Live + reproduce inside cells, causing cell damage

How to reduce the spread of pathogens?

• 5

1. Wash hands before eating (basic hygiene)

2. Provide people w clean drinking water

3. Reduce direct contact betw individuals

4. Isolate patients w highly infectious diseases

5. Vaccination

What does drinking water normally contain to reduce the spread of pathogens?

Chlorine to kill microbes

How do bacteria divide?

Binary fission

• Splitting in 2

Can viruses be killed by antibiotics?

No

Droplet infection

Inhalation of droplets containing pathogens from sneezes + coughs.

How are pathogens spread by droplet infection?

1. Infected person coughs / sneezes → expels droplets

2. Virus passes into diff person when droplets inhaled

What can measles cause if complications develop?

Damage to breathing system + brain

Why are most children vaccinated against measles when they are very young?

Can be fatal in sevre cases

What does HIV initially cause?

Flu-like illness

How does the immune system become damaged in HIV + what does this lead to?

• Virus attacks cells of patients IS

• Overtime, IS becomes severely damaged

• IS can’t fight of other infections + cancer cells (that other people could easily deal w)

In HIV when the immune system becomes severely damaged, what can the patient not fight off?

• Cancer cells

• Other infections

If the patient’s IS can’t fight off other infections, what does this lead to?

Patient can:

• Easily contract other infections

• Develop cancer

When is the HIV disease fatal?

When patient has:

• Late stage HIV / AIDS

When does late stage HIV / AIDS occur?

When the body’s IS becomes so badly damaged it can no longer deal with other infections / cancers

What do antiretroviral drugs do?

Stop the virus from multiplying inside the patient → so virus doesn’t damage patients IS

Why should a patient with HIV take antiretroviral drugs?

• Don’t go on to develop AIDS

• Can lead a normal life expectancy

Are antiretroviral drugs a cure for HIV / AIDS?

No

• Patient must take the drugs for the rest of their life

How does HIV spread when drug users share infected needles?

Blood passes in the needle from 1 person to another

Tobacco mosaic virus (TMV)

Widespread plant pathogen affecting many species of plants, incl tomatoes

How does TMV causing a mosaic pattern of discoloration of the leaves affect plants?

• Rate of PS reduced

• So plant growth reduced

How can bacteria be killed?

Antibiotics

How is the spread of salmonella controlled in the UK?

Poultry are vaccinated against Salmonella

What causes the symptoms of salmonella?

Salmonella bacteria secrete toxins

Where can salmonella bacteria be found?

Poultry, eg chicken

What is gonorrhoea caused by?

Bacteria

Gonorrhoea

Sexually transmitted disease (STD)

How was gonorrhoea easily treated in the past?

Antibiotic penicillin

Why is it hard to treat gonorrhoea with penicillin antibiotics now?

Antibiotic-resistant strains of bacteria are now common

• Diff antibiotics used to treat it

Why should people use barrier methods of contraception (condom) during SI to reduce spread of gonorrhoea?

Prevents bacteria from passing from person to person

Why should people who have unprotected sex be tested for gonorrhoea to reduce spread of gonorrhoea?

Then they are treated with antibiotics to kill the bacteria before they pass it to another person

What is rose black spot caused by?

Fungus

How does RBS affect the plant?

• Rate of PS falls

• Reduced growth of plant

Fungicides

Chemicals that kill fungi

What causes malaria?

Protist

Can a protist pass directly from 1 person to another?

No

Vector

Living organisms that carries pathogens from an infected organism to a healthy one

What vector is part of the malarial protist life cycle?

Mosquito

Malarial protist life cycle

1. Malaria infected person bitten by mosquito

2. Malaria pathogen passes into mosquito

3. Mosquito bites a diff person + passes malaria pathogen to them

How to prevent the spread of malaria

1. Prevent the vectors (mosquitos) from breeding

2. Use mosquito nets when sleeping to avoid being bitten

Where do mosquitos breed?

Still water

How to prevent mosquitoes from breeding?

1. Drain areas of still water

2. Spray areas of still water w insecticide (kills mosquitos)

Viral diseases

1. Measles

2. HIV

3. TMV

Bacterial diseases

1. Salmonella

2. Gonorrhoea

2 main defence systems against pathogens

1. Non-specific defence system

2. Immune system

Role of non-specific defence system

Prevent pathogens from entering the human body

4 parts of the non-specific defence system

1. Skin

2. Nose

3. Trachea + bronchi

4. Stomach

Cilia

Tiny hairs covered with mucus that can trap pathogens

What pathogens would HCl in the stomach help kill

Microorganisms in the:

• Mucus swallowed

• In food

Example of when the non-specific defence system doesn’t work

Skin damaged → pathogens can invade body + enter BS

What can pathogens do once they are inside the body?

Multiply + damage healthy tissue

2 roles of the immune system

1. Destroy pathogens + toxins they produce

2. Protect us incase the same type of pathogen invades us in the future

What does the immune system involve?

WBC

What does the IS try to do if a pathogen enters the body?

Destroy the pathogen

How do WBC defend against pathogens?

1. Phagocytosis

2. Antibody production

3. Antitoxin production

Phagocytosis

WBC ingest + destroy pathogens

How does phagocytosis work?

1. WBC detects chemicals released from pathogen + moves towards it

2. WBC ingests the pathogen

3. WBC uses enzymes to destroy the pathogen

How do WBC destroy pathogens by making antibodies?

1. WBC produces antibodies

2. Antibodies stick to pathogen → triggers pathogen to be destroyed

Antibodies

Protein molecules produced by WBC

Are antibodies general or specific?

Specific

What is meant by antibodies are specific?

1. WBC produces antibodies against a specific pathogen

2. Those antibodies only protect against that certain pathogen (nothing else)

Do antibodies stay in the blood for a long or short time?

Long

Why is it good that antibodies remain in the blood for a long time?

They can protect us if we ever get infected again with the same pathogen

How do WBC destroy pathogens by making antitoxins?

1. WBC produce antitoxins

2. Antitoxins stick to toxin molecules + prevent them from damaging cells

What do antitoxin stick to?

Toxin molecules

What can plants be infected by?

• Pathogens

• Insects

What insects can plants be infected by?

Aphids

How do aphids affect plants?

Extract nutrients (eg sugars) from plants → stunting its growth

Are insects a pathogen?

No- can’t cause infectious disease

• But can be a vector

How to detect plant diseases?

• 7

1. Stunted growth

2. Spots on leaves

3. Areas of decay (rot)

4. Growths

5. Malformed stems or leaves

6. Discolouration

7. Presence of pests

How to identify plant diseases?

1. Reference a gardening manual or website

2. Take infected plant to a lab to identify the pathogen

3. Use testing kits containing monoclonal antibodies