12.3

Question 1

What is direct transmission?

Answer 1

The pathogen is transferred directly from one individual to another

Question 2

What are examples of direct contact?

Answer 2

• Direct transmission (contagious diseases)
• Kissing/sexual intercourse and body fluids (bacterial meningitis)
• Direct skin to skin contact e.g ring room, athletes foot
• Microorganism from faeces transmitted on hands, for example diarrhoeal diseases

Question 3

What are examples of inoculation?

Answer 3

• through a break in the skin (e.g during sex- HIV/AIDS)
• From an animal bite- for example rabies
• Through a puncture wound or through sharing needles (e.g septicaemia)

Question 4

What are examples of ingestion?

Answer 4

taking in contaminated food or drink, or transferring pathogens from mouth to hands like amoebic dysentery

Question 5

What is indirect transmission?

Answer 5

where the pathogen travels from one individual to another indirectly via an intermediate

Question 6

What are examples of indirect transmission?

Answer 6

Fomites:

• inanimate objects like bedding, socks or cosmetics can transfer pathogens like athletes foot.

Droplet infection (inhalation):

• minute droplets of saliva and mucus are expelled from your mouth as you talk, cough or sneeze
• These contain pathogens where healthy individuals breathe the droplets they may become infected
• These include tuberculosis and COVID-19 and Influenza

Vectors

• A vector transmits communicable pathogens from one host to another
• For example mosquitoes transmit malaria, rat fleas transmit bubonic plague and dogs, foxes and bats transmit rabies
• Water can act as a vector for diarrhoeal diseases

Question 7

What is the transmission between animals and humans?

Answer 7

some communicable diseases can be passed from animals to people for example the bird flu strain H1N1 and brucellosis which is passed from sheep to people

These can be reduced by minimising contact with animals and washing hands

Question 8

What are the factors affecting the transmission of communicable diseases?

Answer 8

• overcrowded living and working conditions
• Poor nutrition
• A comprised immune system eg having HIV or AIDS or needing immunosuppressant drugs after transplant surgery
• Poor disposal of waste
• Climate change- could introduce new vectors and diseases for example increased temperatures promote the spread of malaria as the mosquito vector can survive across a wider area
• Culture and infrastructure
• Socioeconomic factors- lack of trained health workers and insufficient public warning where there is an outbreak of disease can also affect transmission rates - also lack of education such as telling people to have safe sex by wearing condoms

Question 9

What is the transmission of pathogens in plants?

Answer 9

direct contact of a healthy plant with any plant of a diseased plant e.g rich rot, tomato blight etc.

Question 10

What is indirect transmission in plants?

Answer 10

Soil contamination

• Infected plants often leave pathogens (bacteria or viruses) or reproductive spores from protoctista or fungi in the soil. These can infect the next crop.

Vectors

• wind- bacteria, viruses, fungal or oomycete spores may be carried on the wind
• Water- spores swim in the surface film of water on leaves, raindrop splashes carry pathogens and spores etc.
• Animals- insects and birds carry pathogens and spores from one plant to another as they feed. Insects such as aphids inoculate pathogens directly onto plant tissue
• Humans- pathogens and spores transmitted by hands, clothing, vomited, farming practises and transporting plants and crops around the world.

Question 11

What factors affect the transmission of communicable diseases in plants?

Answer 11

• planting varieties of crops that are susceptible to disease
• Overcrowding increases the likelihood of contact
• Damp, warm conditions increase survival and spread of pathogens and spores
• Climate change- increased rainfall and wind promote the spread of diseases, changing condition allow animal vectors to spread to new areas; drier conditions may reduce to the spread of disease.

Question 12

How can we prevent the spread of communicable diseases in humans?

Answer 12

• hand washing
• Disinfectant
• Personal hygiene
• Food hygiene
• Needle hygiene
• Handkerchiefs
• We can isolate infected people and keep them from infected people
• We can also destroy vectors such as mosquitos which transmit malaria