Chapter 12 Communicable Diseases

Question 1

Name the types of Pathogens

Answer 1

Viruses
Bacteria
Protoctista
Fungi

Question 2

Definitions of communicable diseases and pathogens

Answer 2

Diseases that can be passed from one organism to another

A microorganism that causes disease

Question 3

What are the modes of pathogen action

Answer 3

1) Damaging host cells directly- Take over cell metabolism, digest cells, break cells open
2) Producing toxins that damage host- poison cells, break down cell membranes, damage enzymes, prevent cell division

Question 4

What is the difference between direct and indirect transmission?

Answer 4

Direct is when the pathogen is transferred directly to another organism but indirect is where the pathogen travels from one organism to another indirectly

Question 5

Examples of direct and indirect transmission in animals are….

Answer 5

Direct:
Direct contact (kissing, transfer of bodily fluid, skin to skin contact etc)
Inoculation (through break in skin, from an animal bite)
Ingestion (Taking in contaminated food, or touching mouth with dirty hands)

Indirect:
Fomites (bedding, clothes)
Droplet infection
Vectors (insects like mosquitos and water)

Question 6

A Bacterial plant infection……

Answer 6

Ring Rot
Spread directly via infected potato tubers and via direct contact
Spread indirectly by infected machinery and bags/boxes
symptoms are a rot develops around vascular tissue

Question 7

Viral infection affecting plants….

Answer 7

TMV (tobacco mosaic virus)
Spread via direct transmission between infected and uninfected leaves
Spreads indirectly by machinery and tools and also humans can act as vectors as they can carry it on there hands
yellowing of leaves and a mosaic pattern develops

Question 8

Fungal infection affecting plants….

Answer 8

Black sigatoka

Causes a black streak in leaves and reduces leaf area and also causes premature ripening

Question 9

Protista infection in plants….

Answer 9

Blight
Can be spread via direct contact
But can be indirectly spread by spores that can wash into the soil where they infect young tubers
Symptoms are watery rot of leaves which then turn brown and shrivel and brown lesions may appear

Question 10

Bacterial infection in humans…

Answer 10

Tuberculosis
Spread via droplets 
Symptoms include:
    - lack of appetite
    - fever and night sweats
    - fatigue
    - cough or breathlessness

Question 11

Viral infection in humans…

Answer 11

HIV/AIDS (impacts and weakens the immune system)
Transmitted directly through unprotected sex or indirectly by sharing needles 
Symptoms:
   - Fever
   - sore throat
   - rash
   - Tiredness
   -muscle pain

Question 12

Fungal infection in humans…

Answer 12

Athletes foot (Tinea Pedis)
Can be passed on directly via contact 
or indirectly via fomites like towels, clothing etc
Symptoms:
   - Dry flaky skin on feet
   - Itchy red rash

Question 13

Protista infection in humans…

Answer 13

Malaria
Spread indirectly via a vector
Symptoms:
   - fever
   - Sweats and chills
   - vomiting
   - muscle pains
   - diarrhoea

Question 14

Examples of direct and indirect transmission in plants…

Answer 14

Direct transmission:
-Direct contact between infected and non infected
plants
Indirect transmission:
-Soil contamination (reproductive spores in soil)
- Vectors (wind, animals, water, humans)

Question 15

Factors that affect transmission in animals and plants…

Answer 15

Animals:
  - overcrowding 
  - poor nutrition
  - poor waste disposal 
  - socioeconomic factors (lack of health care workers)
Plants:
  - Overcrowding and planting crops susceptible to 
    disease
  - damp warm conditions
  - climate change
  - poor nutrition

Question 16

Primary defences against pathogens in animals?

Answer 16

• Skin = healthy flora that outcompete pathogen
• expulsive reflexes like sneezing/coughing
• mucous membranes with cilia
• lysozymes in tears
• blood clotting
• Inflammatory response

Question 17

Physical plant defences?

Answer 17

Callose = deposited in plasmodesma and cell walls near infected cell
Tyloses = balloon like swelling that fills the xylem
Waxy cuticles
Bark
Stomatal closure
oxidative bursts (cell suicide)

Question 18

Chemical plant defences?

Answer 18

Phenols - have antibiotic/fungal properties
Hydrolytic enzymes - break down cell walls of invading pathogens
alkaloids - e.g. caffeine and cocaine give a bitter taste and can also inhibit metabolic activity so less animals will eat it and so less damage for pathogens to enter

Question 19

Inflammatory response?

Answer 19

Mast cells activated in damaged tissue
Release histamines and cytokines
Histamines: -cause BV to dilate so there’s an increased BF to the area so increased redness and swelling
-Cause BV to become leaky so blood plasma forced out is forced out = swelling
Cytokines attract WBC’s

Question 20

How do fevers help to get rid of pathogens?

Answer 20

Cytokines stimulate hypothalamus to reset thermostat
This causes a temp increase
Increased temp inhibits pathogen reproduction
Specific immune system works faster at higher temps

Question 21

NON-Specific immune system

Answer 21

OPSONINS bind to antigens and enhance ability of phagocytes to bind to pathogen
CYTOKINES are released by phagocytes after they have engulfed a pathogen to alert other ‘body is under attack’
PHAGOCYTES engulf pathogen–> Neutrophils digest
–>Macrophages=APC

Question 22

Phagocytes mode of action?

Answer 22

• Pathogens release chemicals that attract phagocytes
• Recognise proteins on pathogen as non-self
• Engulf the pathogen into a phagosome
• combines with a lysosome –> Phagolysosome
• Enzymes from lysosomes break down pathogen