The transmission of communicable diseases 12.3

Question 1

what are the 2 overall types of transmission of pathogens

Answer 1

Direct and indirect transmission

Question 2

what is direct transmission

Answer 2

In direct transmission the pathogen is transferred directly from one individual to another

Question 3

What are the main methods of direct transmission

give examples of diseases that can come about from each

Answer 3

Direct contact

• contact with fluids of another (bacterial meningitis, STI’s, HIV/AID’s)
• skin to skin contact (ring worm & athlete foot)

Inoculation

• through a break in the skin (rabies, septicemia)

Ingestion

• eating contaminated food/drink
• transferring pathogens to mouth from hands (amoebic dysentery)

Question 4

what in indirect transmission

Answer 4

This is where the pathogen travels from one individual to another indirectly

Question 5

what are the main methods of indirect transmission

Answer 5

Fomites:

• inanimate objects that transfer pathogens (athletes foot, gas gangrene)

Droplet inhalation:

• (influenza & tuberculosis)

Vectors:

• A vector transmits communicable pathogens from one host to another.
• examples include animals, water and humans
  (humans can transmit foot and mouth disease)

Question 6

Can transmissions between animal and humans occur

Answer 6

Some communicable diseases can be passed from one animals to people, for example bird flu

Question 7

What are some factors that can increase the probability of catching a communicable disease

Answer 7

• overcrowded living and working conditions
• poor nutrition
• a comprised immune system, including (in humans) having HIV/AID’s or needing immunosuppressantdrugs after transplant surgery
• (in humans) poor disposal of waste, providing breeding sites for vectors
• climate change -this can introduce new vectors and new diseases for example increased temps promote the spread of malaria
• culture and infrastructure, in many countries traditional medical practises can increase transmission
• socioeconomic factors, for example lack of trained health workers

Question 8

• How does direct transmission occur in plants
• what are some examples of diseases that can be brought about by this

Answer 8

• involves direct contact of a healthy plant with any part of a diseased plant
• ring rot, potato blight, black Sigatoka

Question 9

What are the main methods of indirect transmission in plants

Answer 9

• soil contamination
• vectors

Question 10

How does soil contamination cause indirect transmission between plants

Answer 10

Infected plants often leave pathogens (bacteria or viruses) or reproductive spores from protoctista or fungi in the soil. These can infect the next crop. Examples are black Sigatoka spores, ring rot bacteria. Some pathogens (often as spores) can survive the composting process so the infection cycle can be completed when the contaminated compose is used

Question 11

How do vectors cause indirect transmission between plants

Answer 11

• wind-bacteria, viruses and fungal or oomycete spores may be carried on the wind (black Sigatoka blown between Caribbean islands)
• water-spores swim in the surface film of water on leaves; raindrop splashes carry pathogens and spores
• animals-insects and birds carry pathogens and spores from one plant to another as they feed. Insects such as aphids inoculate pathogens directly into plant tissues
• humans-pathogens and spores are transmitted by hands, clothing fomites, farming practices and by transporting plants and crops around the world (ring rot survives on farm machinery)

Question 12

What is an oomycete

Answer 12

group of several hundred organisms that include some of the most devastating plant pathogens.

Question 13

what are some factors that affect the transmission of communicable diseases in plants

Answer 13

• planting varieties of crops that are susceptible to disease
• over-crowding increases the likelihood of contact
• poor mineral nutrition reduces resistance of plants
• damp, warm conditions increase the survival and spread of pathogens and spores
• climate change-increased rainfall and wind promote the spread of diseases; changing conditions allow animal vectors to spread to new areas; drier conditions may reduce the spread of disease

Question 14

what are some ways in which you could prevent the transmission of communicable diseases in plants

Answer 14

• leave plenty of room between plants to minimise the spread of pathogens
• clear fields as thoroughly as possible-remove all traces of plants from the soil at harvesting
• rotate crops-the spores or bacteria will eventually die if they do not ave access to the host plant
• follow strict hygiene practices-measures such as washing hands, washing boots, sterilising storage sacks, washing down machinery
• control insect vectors

Question 15

What are some ways to prevent the transmission of communicable diseases in humans

Answer 15

• hand washing-regular hand washing is the single most effective way of preventing the spread of many communicable diseases
• improvements in living and working conditions (reducing overcrowding, ensuring good nutrition)
• disposal of both bodily and household waste effectively