Communicable diseases Flashcards
Disease definition
Condition that affects the normal functioning of an organism
Types of pathogens
Bacteria
Viruses
Fungi
Protoctists
Classification of bacteria
- Shapes (bacillus, coccus, vibrio)
- Cell walls (gram positive and gram negative)
Bacterial diseases
Ring rot
Bacterial meningitis
TB
Viral diseases
AIDS
Influenza
Tobacco mosaic virus (TMV)
Fungal diseases
Black sigatoka
Ringworm
Athlete’s foot
Protictist diseases
Potato blight
Malaria
Viruses mode of damaging host tissue
- they affect the cell metabolism
- viral genetic material enters the host DNA
- virus uses the new cell to replicate new viruses which then burst out of the cell and destroying it
- spread out to infect neighbouring cells
Protoctista mode of damaging host tissue
- break cells but don’t take over the genetic material
- digest and use the cell contents to reproduce
Fungi mode of damaging host tissue
- digest living cells and destroy them
- produce toxins which affect the cell
Bacteria mode of damaging host tissue
- produce toxins that damage and poison the cell
- toxins can damage the cell membrane, inactivate enzymes, interfere with host’s genetic material
Types of transmission
Direct and indirect
Indirect transmission (animals)
- fomites (inanimate objects such as bedding, socks, cosmetic brushes)
- droplet infection (saliva or mucus)
- vectors (such as flies, water)
Direct transmission (animals)
- direct contact (kissing, body fluids contact, skin to skin contact, microorganisms from faeces)
- ingestion (through food or drink)
- inoculation (break in the skin, puncture wound, needles, animal bite)
Indirect transmission (plants)
- soil contamination
- vectors (wind, water, animals, humans)
Direct transmission (plants)
direct contact of a healthy plant with a diseased plant
Factors affecting communicable diseases (animals)
- overcrowding
- poor nutrition
- compromised immune system
- climate change
- culture and infrastructure
Factors affecting communicable diseases (plants)
- planting species susceptible to disease
- poor mineral nutrition
- poor water availability
- damp, warm conditions increase spread of disease
- climate change
Plant defences against pathogens
- physical
- chemical
Mechanism of recognition of attack in plants neurons
- Pathogenic enzymes break down cell membrane and the products are recognised by the receptors of the cell
- Signalling molecules alert nucleus to attack
- Polysaccharides (callose and lignin) are produced to strengthen the cell walls
- Defensive chemicals signal the other cells before they are attacked
- Some defensive molecules attack the pathogen directly
Physical defences
- Callose is synthesised and deposited b/n cell walls in order to prevent the pathogens from entering the neighbouring cells
- lignin and callose are deposited to form a barrier against infection
- callose deposits between sieve plates
Chemical defences
- insect repellents
- insecticides (pyrethrins)
- antibacterial compounds including antibiotics (phenols, defensives, lysosomes)
- antifungal compounds (phenols, caffeine, saponins, chitanases)
- general toxins (chemicals can be broken down to form cyanide compounds which are toxic)
- anti-oomycetes (glucanases)
Non-specific animal defences against pathogens
- skin (skin flora with with healthy microorganisms)
- mucus membrane lining on airways and body tracts
- lysozyme in tears and urine and acid in stomach
- repulsive reflexes such as coughing, sneezing, vomiting, and diarrhoea
- blood clotting and wound repair
- inflammatory responses
- fever
- phagocytosis
Inflammatory response
Mast cells are activated in damaged tissue and release chemicals:
- histamines make blood vessels dilate, causing redness and they become more leaky, so blood plasma is forced out and forms tissue fluid, causing swelling and pain
- cytokines attract white blood cells (phagocytes) to the site so they can undergo phagocytosis
Blood clotting
- Damaged tissue leads to platelets being activated, which release THROMBOPLASTIN
- THROMBOPLASTIN + CA2+ ions catalyse the formation of THROMBIN from PROTHROMBIN
- THROMBIN catalyses the production of FIBRIN from fibrinogen
- Fribrin + collagen fibres forms a mesh to forms a blood clot
