12.3 - Transmission of Communicable Diseases

Question 1

What are the 3 methods of direct pathogen transmission between animals?

Answer 1

• Direct Contact - kissing, intercourse (bodily fluids) e.g. bacterial meningitis and STDs. Faecal microbes transmitted on hands
• Inoculation - through break in skin, during sex (HIV/AIDS). Animal bites, rabies. Puncture through sharing needles (septicaemia)
• Ingestion - taking in contaminated food.dirnk, transferring pathogens to mouth from hands (diahorreal diseases)

Question 2

What are the 3 methods of indirect pathogen transmission between animals?

Answer 2

• Fomites - inanimate objects - beddings, socks - transfer pathogens. E.g. athletes foot, gas gangrene, Staphyloccocus infections
• Droplet Infection (inhalation) Minute saliva/mucus droplets expelled when you talk, sneeze or cough. If droplets have pathogens that others inhale, they become infected, e.g. TB, flu
• Vectors - vector transmits communicable pathogens from host to another. Not always animals, e.g. mosquitos (malaria), dogs (rabies). Water is also a vector

Question 3

How can pathogens/disease be transmitted between animals and humans?

Answer 3

• E.g. bird flu strain H1N1 and brucellosis can be passed from animal (sheep) to human
• Minimising close contact with animals & washing hands after contact reduces infection rate.
  
  • People can be vectors for some animal diseases, fatal results. E.g. foot and mouth disease

Question 4

What are the factors affecting transmission of communicable diseases between animals?

Answer 4

• Overcrowding working/living conditions
• Poor nutrition
• Compromised immune system – e.g. using immunosuppressant drugs, having HIV/AIDS
• Climate change – introduces new vectors and disease, e.g. increased temp. promotes malaria spread
• Infrastructure and culture – traditional medical practises increase transmission
• Socioeconomic factors – lack of trained health workers, insufficient public guidance when outbreak occurs

Question 5

What is a method of direct transmission of disease between plants?

Answer 5

Direct contact between healthy plants with any part of a diseased plant.

Question 6

What are methods of indirect transmission of disease between plants?

Answer 6

• Soil Contamination - infected plants leave pathogens or reproductive spores of protoctista/fungi in soil. Some pathogens survive composting process so infenction cycle is completed when composted soil is reused.
  
  • Vectors -
    • Wind - bactrea, viruses, fungal spores carried in wind
    • Water - spores swim in surface film of water on leaves (raindrop splashes)
    • Animals - insects and birds carry pathogens and spores from one plant to another as they feed
    • Insects - aphids innoculate pathogens into plant tissue
    • Humans - pathogens and spored transmitted by hands, clothing, fomites, farming practice.
    • E.g. ring rot in machiner

Question 7

What factors affecting transmission of communicable diseases in plants?

Answer 7

• Planting variety of crops susceptible to disease
• Over-crowding increases likelihood of contact
• Poor mineral nutrition reduces plant resistance
• Damp, warm conditions increase survival chance and pathogen/spore spread
• Climate change – increased rainfall and win promotes disease spread, changing conditions allow animal vectors to spread, drier conditions reduce disease spread.