Infectious diseases Flashcards
What is a pathogen?
An organism that causes disease
What does ‘communicable disease’ refer to?
Disease that spreads between organisms.
What does bacteria do?
Produces toxins
—–> Inhibits certain enzyme action.
Leads to build-up of toxic chemicals in the body.
Examples of bacterial infections:
Tuberculosis —-> Damages lung tissue and causes respiratory issues
Ring rot —–> Potatoes/tomatoes: damages leaves, prevents photosynthesis from occurring.
Bacterial meningitis
What do fungi do?
Produce toxins
Digest cells
Saprophytic = digest and feed on dead organisms
Causes lack of cell function.
Examples of fungi:
Athletes foot —> warm/moist areas of the feet = digest cells
Black Sigatoka —-> Destroys chloroplasts = limits amount of glucose which is made.
Ringworm.
What do viruses do?
Hijack cells to reproduce.
Inject genetic material into host cell.
Genetic material combines with host cell DNA (using reverse transcriptase)
Viral DNA/RNA and proteins made using host cell own resources.
Causes cell to burst
Examples of viral diseases.
AIDs: T-Helper cell targeted by HIV —-> cannot send signals to help body produce antibodies.
Tobacco Mosaic Virus: Produces mosaic pattern of discolouration –> yellow/brownish
Influenza
What do protoctists do?
Hijack cells to reproduce.
Examples of protoctists:
Malaria —> vector = female mosquitoes
Transfers the protists into the bloodstream.
Potatoe blight:
Damages leaves —> limited photosynthesis
Methods of transmission
Direct: one organism to the other
Indirect: Intermediate between two organisms.
Examples of direct transmission:
Direct contact
Incoluation (opening)
Ingestion
Examples of indirect transmission:
Fomites—> inanimate objects
Droplet infection (inhalation)
Vectors—> aphids/mosquitoes (water act as vector)
Contaminated soil
Factors affecting transmission:
Hygenic conditions of the environment
Poor nutrition
Naturally weak immune system
Overcrowding —> high risk of infection
Genetic variation ——> natural suscepibility
Climate change
How do pathogens damage host tissues directly?
Virus: take over cell metabolism
Protoctista: take over cells
+ digest + use cell content to reproduce
Fungi: digest living cells + destroy them
Direct transmission in plants:
Direct contact of healthy plant with diseased plant. –> ring rot, TMV + black sigatoka
Indirect transmission of plants:
Soil contamination: reproductive spores in soil.
–>infect next plant.
Vector: wind, water, animals, humans
Factors affecting transmission of communicable dieases in plants:
- Planting varities of crops susceptible to disease
- Over-crowding
- Poor mineral nutrition reduces resistance of plants
- Damp, warm conditions increase surivival.
- Climate change: increased rainfall + wind promote spread of disease
