Communicable diseases Flashcards
What is direct transmission?
Pathogen is transferred directly from one individual to another
Examples of direct transmission
- Direct contact (kissing, skin-skin, touching)
- Inoculation (break in skin/sex, animal bite)
- Ingestion (taking in contaminated food/drink, transferring pathogen through mouth)
What is indirect transmission?
When pathogen travels from one individual to another indirectly
Examples of indirect transmission
- Fomites (inanimate objects, socks, bed)
- Droplet infection (saliva,mucus infleunza,tb)
- Vectors (from one host to another, water)
What increases the probability of catching a communicable disease?
- Overcrowding
- Poor nutrition
- Compromised immune system
- Poor disposal of waste
- Climate change
- Culture + infrastructure
- Socioeconomic factors
Transmission of pathogens between plants
- Direct (ring rot, TMV, blight, black sigatoka)
- Indirect (Soil contamination, vectors)
Factors affecting the outbreak of communicable disease in plants
- Planting variety of crops, susceptible to disease
- Overcrowding
- Poor mineral nutrition
- Damp, warm conditions
- Climate change (increased rainfall)
Physical defences in plants
- Callose synthesised, deposited in cell wall + membrane
- Act as barriers and lignin
- Blocks sieve plates in phloem
- Deposited in plasmodesmata
Chemical defences in plants
- Insect repellents
- Insecticides
- Anti-bacterial compounds (antibodies)
- Anti-fungal compounds (chitinases break down chitin in fungal cell walls)
- Anti-oomycetes (glucanases)
- general toxins
Inflammatory response
- mast cells release chemicals
- Histamines make blood vessel walls dilate
-> also make them more leaky (blood plasma is forced out) - Cytokines attract white blood cells, dispose by phagocytosis
Blood clotting and wound repair
- Thromboplastin :enzyme that triggers a cascade of reactions - form blood clot
- Serotonin :Smooth muscle in walls of the blood vessel contract, reduce blood supply
What is a non-specific defence?
- Can be chemical or physical barriers
- First line of defence against infection entering body
- Not specific to fight against certain types of pathogen
Barriers to prevent entry of pathogens
- Skin with sebum inhibiting pathogen growth
- Mucous membranes trapping organisms, contain lysozymes
- Lysozymes in tears and urine + stomach acid
- Expulsive reflexes (cough/sneeze)
Stages of phagocytosis
1) Pathogen produce chemicals attracting phagocyte
2) Phagocytes recognise non-human proteins
3) Phagocyte engulf pathogen, encloses it in vacuole called phagosome
4) Combines with lysozymes = phagolysosome
5) Lysosome digest and destroy pathogen
