4.1.2: Transmission of pathogens

Question 1

Describe direct transmission

Answer 1

Passing a pathogen from one host to another, no intermediary.

Question 2

What are a few ways of direst transmission?

Answer 2

• Direct physical contact with infected person or contaminated surface e.g.athlete’s foot.
• Fecal-oral transmission, by eating or drinking food or water contaminated with the pathogen e.g. cholera.
• Droplet infection, pathogen carried in water droplets in air e.g. influenza.
• Transmission by spores, carried in air or reside on surfaces e.g.tetnus, anthrax.

Question 3

What are some social factors that affect transmission?

Answer 3

• Overcrowding (many people living in one house)
• Poor ventilation.
• Poor health.
• Poor diet.
• Homelessness.

Question 4

Describe indirect transmission

Answer 4

Passing a pathogen from one host to another, via a vector.

Question 5

How is the plasmodium parasite transmitted indirectly via a vector?

Answer 5

• A person with malaria has gametes of plasmodium in blood.
• Female anopheles mosquito sucks blood.
• Plasmodium develops and migrates to mosquito’s salivary glands.
• Uninfected person bitten.
• Plasmodium migrates to liver.
• Plasmodium migrates to blood.

Question 6

What are some indirect methods of transmission of plant pathogens?

Answer 6

• Pathogens present in soil infect plants by entering roots.
• Fungi produce spores as a means of sexual or asexual reproduction, spores carried in wind -airborne transmission.

Question 7

Once a plant has been infected by a pathogen, how is the pathogen then redistributed?

Answer 7

• Once in plant, pathogen may infect all the vascular tissue. Pathogens in leaves distributed when leaves shed - pathogens carries back into the soil.
• Pathogens enter fruit and seeds, redistributed with the seeds so offspring are also infected.

Question 8

How can indirect transmission of plant pathogens be caused by insect attack?

Answer 8

• Spores or bacteria become attached to burrowing insect e.g. beetle.
• When beetle attacks another plant, pathogen is transmitted to uninfected plant.
• The beetle is a vector,

Question 9

Why is there a greater variety of diseases in warmer climates?

Answer 9

• Many protoctists, bacteria and fungi can grow and reproduce more rapidly in warm and moist conditions.
• In cooler climates, pathogens may be damaged or killed by cold weather.