4.1.2(Transmission of pathogens)

State what is meant by the term direct transmission

• Passing a pathogen from host to new host, with intermediary

State what is meant by the term indirect transmission

• Passing a pathogen from host to new host via a vector

State what is meant by the term transmission

• Passing a pathogen from an infected individual to an uninfected individual

State what is meant by a vector

• An organism that carries a pathogen from one host to another

Describe the life cycle of pathogens

• Travel from one host to another - Transmission

• Entering the host’s tissues

• Reproducing

• Leaving the host’s tissues

State the 2 types of direct transmission

• Direct physical transmission

• Droplet Transmission

Describe transmission by physical contact can occur and examples

• Physical touching such as touching, kissing, or sexual intercourse with a person who is infected or by touching contaminated surfaces(including soil) that harbour pathogens

• Examples: HIV, Bacterial meningitis, ring worm, Athlete’s foot

Describe how to mitigate transmission by physical contact

• Hygiene: Washing hands regularly - especially after the toilet.

• Keeping surfaces clean - door handles

• Cleaning and disinfecting cuts and abrasions

• Sterilising surgical equipment

• Using condoms during sexual intercourse

Describe how droplet transmission can occur and examples

• Droplet infection , in which a pathogen is carried in the tiny water droplets in the air.

• Examples: Tuberculosis, Influenza

Describe how to mitigate droplet transmission

• Catch it - Bin it - Kill it

• Cover your mouth when coughing or sneezing. Use a tissue and ensure the tissue is disposed of correctly

State 6 factors which affect transmission of pathogens

• Overcrowding

• Poor ventilation

• Poor health - Particularly is a person has HIV/AIDS, as they are more likely to contract other diseases

• Poor diet

• Homelessness

• Living or working with people who migrated from areas where a disease is more common

State 3 types of indirect transmission

• Faecal-oral transmission

• Spore transmission

• Vector tranmission

Describe how Faecal-oral transmission can occur

• Usually by eating food or drinking water contaminated with pathogens

• Examples: Cholera, food poisoning

Describe how to mitigate Faecal oral transmission

• Treatment of waste water and treatment of drinking water

• Washing all fresh food with treated water

• Careful preparation and thorough cooking of all food to avoid cross contamination

Describe how spore transmission occurs and examples

• Transmission by spores, which are a resistant stage of the pathogen. These can carried in the air or reside on surfaces or in the oil.

• Examples: Anthrax, tetanus

Describe how to mitigate spore transmission

• Using a mask

• Washing skin after contact with soil

Describe the life cycle of a malarial parasite

• An uninfected person gets bitten by a female anopheles mosquito and the plasmodium parasite enter the human host

• The plasmodium migrates to liver

• The plasmodium then migrates to the blood

• The person is now infected with malaria.

• The plasmodium parasite produces gametes in the blood

• Female anopheles mosquito sucks blood out of the host

• The plasmodium migrates to the mosquito’s salivary glands to which it can then infect another person

State 2 methods of direct transmission of plant pathogens

• Through the soil

• Through wind

Describe how pathogens in the soil can infects plants

• They can enter the plant via the roots - especially if these have been damaged as a result of replanting, burrowing animals or movement caused by a storm

Describe how pathogens can infect plants using the wind

• Many fungi produce spores, which can be carried in the wind as a form of airborne transmission

Describe 3 places in the plant which plant pathogens infect and how(if possible) they are distributed

1. It can infect all the vascular tissue

2. It can infect leaves and can be distributed when the leaves shed and carry the pathogen back to the soil where it can grow and infect other plants

3. Pathogens can enter the fruit and seeds, and will be distributed with seeds so that many or all the offspring will be infected

Describe how indirect transmission of plant pathogens occur

• They often happen as a result of burrowing insects:

  • Spores or bacteria become attached to a burrowing insect, such as a beetle, which attacks an infected plant

  • When that beetle attacks another plant, the pathogen is transmitted to the uninfected plant

  • The beetle here is acting as a vector

State an example of a disease in plants that is caused by indirect transmission

• Dutch elm disease is a fungal bacteria which is carried by the beetle, Scolymus Multistriatus - Also known as elm bark tree

Describe how pathogens react differently in hot climates versus in cold climates

• Hot climates:

  • Many pathogens reproduce and grow in warm and moist conditions

• Cold climates:

  • Pathogens may be damaged or even killed by cold weather

  • In cold climates the ability for pathogens to grow and reproduce decreases

Describe how a warm climate affects variety and population of pathogens

• In warmer climates there is a greater variety of pathogens, which means that animals and plants living in these regions are more likely to become infected