Topic 6.2 Non-bacterial pathogens Flashcards
(40 cards)
Anthroponoses
Diseases transmissible from human to human
Zoonoses
Diseases transmissible from living animal to humans (jumps species boundaries)
Sapronoses
Human diseases transmissible from abiotic environment (eg. soil, water, decaying plants, animal corpses etc)
Direct transmission
- Physical contact
- Exchange bodily fluids
- Contact with animals or animal waste
Indirect transmission
- Through intermediates/vectors
- Aerosols/droplets (airborne)
- Vehicle borne (surfaces/objects)
- Food and waterborne
Physical human contact (direct)
Where there is physical contact between an infected person and an uninfected person and the microbe is passed over.
(Chicken Pox, Hep A+B, measles, influenza etc)
Mother to child transmission (direct)
Transmission of a disease from an infected mother to her child during gestation and breast milk.
(HIV, hepatitis, syphilis, thrush)
Physical animal contact (direct)
When a susceptible animal comes in direct contact with an infected animal, its bodily fluids or tissues.
(Rabies, blastomycosis, cat scratch disease, CFJ disease etc)
Intermediates (vectors) (indirect)
Biological vectors may carry pathogens that can be delivered to hosts usually by biting.
(Dengue, yellow fever, Malaria, Japanese encephalitis etc)
Aerosol (airborne) (indirect)
Aerosols and droplets created from coughs and sneezes.
(Influenza, Tuberculosis, common cold, Ebola, Pneumonia)
Vehicle/fomite borne (indirect)
Contaminated surfaces (eg. benches, door handles etc. Could have been contaminated by contact, aerosol or food etc.
(Influenza, tetanus, ringworm, water infection)
Food and waterborne (indirect)
Contaminated food or water sources/ nutritional related.
(Cholera, Cruetzfeldt-Jakob disease, diphtheria, hookworm)
Virus structure
Virus entry
All viruses must get their genetic material, DNA or RNA, into a hot cell to replicate and start their life cycle.
- Some viruses, such as ones that infect bacterial cells (bacteriophages) inject only their DNA inside the host cell.
- Other viruses such as those that infect animal cells can be wholly engulfed (endocytosis) or have their lipid envelope fuse with the cell membrane.
Mode of transmission: Influenza
1) Droplets form coughs and sneezes
2) Direct contact with an infected person
3) Contact with contaminated surfaces (fomites)
4) Zoonotic infection: contact with animal
Mode of infection: Influenza
–> Ciliated epithelial cells of the respiratory tract.
1) Injects viral RNA into ciliated epithelial cells (bacteria enters a cell by endocytosis and forms a vesicle).
2) Viral RNA hijacks cell biochemistry to produce new virions; the virus insert sits DNA into the cell.
3) Cell lysis releases virions.
(Lytic cycle).
The Pathogenic effect: Influenza
- Lung inflammation caused by viral infection of the respiratory epithelium.
- Death of cili leave airways open to infection.
Headache, coughing & sneezing, sore throat, vomiting, fever, muscular/joint pain.
–> Symptoms last roughly 5-7 days.
Influenza
- Respiratory disease.
- Short incubation period.
- Mutate frequently so overcome immune response.
- 3 strains.
- Antigen markers e.g H1N1.
- Transmitted mainly airborne or contact with animal droppings or surfaces (fomites).
Treatment of flu
- No cure
- Vaccines
- Spreads as people carry on with flu and spread it
- Anti viral medicines
Fungi
- Fungi are single celled
- They have walls made of chitin and glycan
- They do not photosynthesise
- Spores are used for reproduction
Hyphae
Long thread-like filaments.
Many fungi grow as hyphae.
Some fungi can:
- Be poisonous
- Cause allergies
- Cause parasitic diseases (growing on areas of skin eg. athletes foot)
—> its rare for fungi to cause serious harm to humans.
Case study
Stem Rust Fungus (Puccinia graminis): Mode of transmission
- Wind dispersed urediniospores.
- Plants may become infected from parts of infected plant left in the soil.
—>The pattern of infection helps determine whether the source of infection is a local bush (a fan of infection) or a distant wheat field.
Case study
Stem Rust Fungus (Puccinia graminis): Mode of infection
- A hypha emerges form the spore and penetrates one of the stoma of the leaves or stem.
- The hypha secretes enzymes (eg. cellulases) which digest the plant cells and the nutrients which are absorbed into the fungus.
- The hyphae branch to form a mycelium that feeds and grows on the stem or leaves of a wheat plant.
- Grows best when it has hot days (25-30°C), mild nights (15-20°C) and wet leaves.
–> Spores need water to germinate.
