Topic 6.2 Non-bacterial pathogens Flashcards
What adaptions of malaria mean that an effective vaccine has not been made yet?
- parasite spends a lot of time hidden from immune system in bodily cells
- antigens on its surface change frequently (hard for immune system to recognise them)
What causes antigen variability?
- random genetic mutation changes DNA base sequence
- results in different sequences of codons on mRNA
- different primary structure of antigen = H-bonds, ionic bonds, disulfide bridges form in different places in tertiary structure
- different shape of antigen
Explain how antigen variability affects the incidence of dieases?
- memory cells no longer complimentary to antigen (individual not immune and can catch the disease more than once/ can’t recognise pathogen e.g. HIV)
- many varieties of a pathogen so difficult to develop a vaccine containing all antigen types
Why is it so difficult to control the spread of antibiotic resistant bacteria?
horizontal conjunction transfers plasmids with resistance allele from one bacterium to another rapidly
Define modes of transmission
the different ways a pathogen is spread from one host to another
What’s a zoonotic infection?
an infection in a person caused by a pathogen that can cross the species barrier from other animals
Define the mode of infection
the way a pathogen causes infection
What’s the pathogenic effect of a microorganism?
the symptoms of disease it causes
Why do fungal pathogens have a large effect on humans even if they rarely cause human diseases?
many plant diseases that threaten human food security are caused by fungal infections
Give another name for stem rust fungus
Puccinia graminis
What are the modes of transmission of stem rust fungus?
- wind carries spores from infected plants
- infected plant fragments in the soil
State the mode of infection for stem rust fungus
- spores germinate in water on plant
- hyphae enter through stomata of the leaves
- enzymes like cellulase digest the plant cells (secreted from the hyphae)
- nutrients are then absorbed into the fungus
- hyphae branch to form mycelium that feed and grows, hidden in the plant
Define hyphae (single-hypha)
thread-like fungal structures that are single units of the mycelium
Define mycelium
a fungal body made up of a mass of thread-like hyphae
What are the pathogenic effects of stem rust fungus?
- nutrients lost to the fungus
- pustules break the epidermis so it is difficult to control transpiration
- stem weakened and may collapse in the wind (cannot be harvested effectively)
- mycelium grows into vascular tissue, absorbing water and nutrients
In what ways does modern farming encourage the growth of stem rust fungus?
- high nitrate levels favour the fungus (fertilisers)
- irrigate regularly which provides water for stem rust spores to germinate
- not disturbing the soil means bits of infected plants are more likely to be on top of the plant to infect the new crop
How can stem rust fungus be controlled and reduced?
- bigger spaces in between plants to reduce moisture and increase distance for spore to travel
- reducing application of fertilisers
- use of earlier-maturing crops which avoid time of max spread
- remove any wild Berberis so part of lifecycle is interrupted
- fungicides control growth of stem rust but expensive
What are the optimum conditions for stem rust fungus?
- hot days (25-30 degrees)
- mild nights (15-20 degrees)
- wet leaves (from wither rain, dew or irrigation)
What type of pathogen is influenza?
viral pathogen
What are the modes of transmission for influenza?
- droplet infection
- direct contact with animal droppings
- direct contact with virus-filled mucus
- direct contact with surfaces contaminated with virus
State the mode of infection for influenza
- infects ciliated epithelial cells of the lungs
- viral RNA takes over the biochemistry of the cell
- cell produces new virus particles
- the cell lyses, releases viruses and dies
What are the pathogenic effects of influenza?
- fever, shivering, sweating
- loss of appetite
- severe headaches
- shortness of breath
- sore throats
- disease lasts for around 5-7 days
- lungs and heart can be severely affected
- secondary bacterial infection may occur where epithelial tissue is damaged
- full recovery 6-12 weeks
Why does having the flu make people more susceptible to secondary infections?
the death of ciliated epithelial cells of the trachea and bronchi leave the airways open to infection (secondary bacterial infection)
What is the malaria parasite?
Plasmodium spp.