Module 4 Flashcards
Pathogen =
a microorganism that causes disease.
Bacteria
• Can rapidly multiply in the right conditions • Cause disease by damaging cells or producing toxins that are harmful • Eg tuberculosis, bacterial meningitis, ring rot (plants)
Viruses
• Invade cells and take over the protein-synthesising organelles • Infect the cells with new DNA • Host cells eventually burst and release new copies of the viral DNA • Eg HIV/AIDS, influenza, tobacco mosaic virus (plants)
Fungi
• In animals, cause redness and irritation • This is due to hyphae released from the fungus • Eg black sigatoka (bananas), ringworm (cattle), athlete’s foot
Protoctista
• Feed on cell contents as they grow • Eg malaria, potato blight
Tuberculosis • Cause
• Bacterial • Mycobacterium tuberculosis • Divides slowly (every 20 hours) • Can survive for 6 months outside body
HIV/AIDS • Cause
• Virus • Human immunodeficiency • Attacks and destroys immune cells weakens immune system • Open to range of opportunistic diseases • Secondary infection
Malaria • Cause
• Eukaryotic organism • Plasmodium falciparum
Tuberculosis • Transmission
• Sufferer cough, catapulting droplets of saliva into air • Saliva contain tuberculi bacilli • High speed • Reach over 1-2m • 1 sneeze can have up to 40,000 droplets
Tuberculosis • Global Impact
worldwide • 1% of world newly infected each year • 8.8 million cases • 34% new cases occur in S.E. Asia • 1.6 million deaths
HIV/AIDS Transmission
• Exchange of bodily fluids • Sharing of hypodermic needles • Across placenta during child birth • From mother to baby during breast feeding • Use of unsterilized surgical equipment
HIV/AIDS Global Impact
• Worldwide • 45 million sufferers • 5 million new infections annually • 30 million have died • Rapidly rising in China
Malaria • Transmission
• Spreads by vector • Malarial parasites live in red blood • Feed on hemoglobin • Mosquito will suck parasitical gametes into its stomach • Gametes fuse to form zygotes in mosquito stomach • Plasmodium develops and moves to salivary glands • Mosquito bites person, injecting saliva • Plasmodium enters person • Migrates to liver • Multiplies and passes into blood • Cycle repeats
Malaria • Global Impact
• Kills 3 million annually • 300 million affected worldwide • limited to regions where anopheles mosquito can live
The most common means of transmission can be identified as five groups
Droplet transmission Physical contact • Faecal-oral transmission Transmission by spores Vector transmission
Droplet transmission
○ E.g. through sneezing - pathogen is contained within mucus ○ Type of direct transmission
Physical contact •
○ Common for skin diseases like ringworm, a fungal disease in cattle, which is spread by an infected animal brushing against an uninfected animal Direct transmission
Faecal-oral transmission
○ E.g. E. coli ○ Transmitted by consumption of food or water with traces of faeces from infected animal ○ Direct transmission
Transmission by spores
○ Spores are a resistant form of the pathogen ○ They can resist extremes of temperature, pH, and even strong disinfectants ○ E.g. anthrax ○ Direct transmission
Vector transmission
○ E.g. malaria ○ The pathogen is carried from one host to another via a vector ○ With malaria the vector is female mosquitoes ○ The pathogen cannot be spread directly from one host to another ○ Indirect transmission
how climate can also contribute to the spread of disease.
• Some vectors only live in hot climates, e.g. mosquitos carrying malaria • Many viruses, protoctists and bacteria survive better in warm climates • Very cold climates can kill pathogens
how Environment can also contribute to the spread of disease.
• Cramped and crowded environments are conducive to spread of disease ○ Droplet infection rate likely to be higher ○ Contact infection also much higher • Dirty environments harbour pathogens ○ E.g. using human sewage to fertilise crops is sometimes done in parts of the world ○ This is likely to cause the spread of faecal-oral pathogen spread
plant Physical barriers
• Passive • Cellulose cell wall • Lignin thickening of cell walls • Waxy cuticles • Bark • Closed stomata • Callose ○ Large polysaccharide deposited in sieve plates in phloem ○ Block movement of pathogens up and down plants to avoid infection of the entire plant • Tylose ○ Balloon-like swelling in xylem ○ Blocks xylem and stops pathogens from travelling this way around the plant
Production of chemicals passive
Terpenoids • Phenols • Alkaloids • Hydrolytic enzymes