Microbiology U11M6 Unit 11 Notes1

2 How Disease is Spread The germ theory of disease – infectious diseases are caused by microorganisms The germ theory of disease – infectious diseases are caused by microorganisms For many pathogens, the human body provides just the right conditions for growth For many pathogens, the human body provides just the right conditions for growth Suitable temperature Suitable temperature Watery environment Watery environment Lots of nutrients Lots of nutrients

Unit 11 Notes3 Agents of Disease Viruses invade & replicate within living cells Viruses invade & replicate within living cells Attach to surface Attach to surface Insert genetic material Insert genetic material Take over functions of host cell Take over functions of host cell Bacteria cause disease in one of 2 ways Bacteria cause disease in one of 2 ways Break down tissues of host for food Break down tissues of host for food Release toxins that harm the body Release toxins that harm the body

Unit 11 Notes4 Agents of Disease Protists cause some very damaging diseases Protists cause some very damaging diseases Malaria – caused by Plasmodium – spread by mosquito bite Malaria – caused by Plasmodium – spread by mosquito bite African sleeping sickness – caused by Trypanosoma – spread by tsetse fly African sleeping sickness – caused by Trypanosoma – spread by tsetse fly

Unit 11 Notes5 Agents of Disease Worms – flatworms & roundworms Worms – flatworms & roundworms Live part of their life cycle in other organisms before infecting humans Live part of their life cycle in other organisms before infecting humans Includes flukes, hookworms, tapeworms Includes flukes, hookworms, tapeworms Fungi Fungi Athlete’s foot – Tinea species Athlete’s foot – Tinea species Ringworm Ringworm Yeast infections Yeast infections

Unit 11 Notes6 How Diseases are Spread Physical contact Physical contact Coughs Coughs Sneezes Sneezes Touching objects Touching objects Sexual contact Sexual contact Behaviors can control transmission Behaviors can control transmission Washing hands Washing hands Covering mouth when coughing or sneezing Covering mouth when coughing or sneezing

Unit 11 Notes7 How Diseases are Spread Contaminated food Contaminated food Food poisoning – eating food containing pathogens Food poisoning – eating food containing pathogens Bacteria grow in warm, partially cooked food Bacteria grow in warm, partially cooked food Proper cooking & refrigeration can prevent Proper cooking & refrigeration can prevent Contaminated water Contaminated water Poor sanitation Poor sanitation Untreated water Untreated water

Unit 11 Notes8 How Diseases are Spread Animal vectors Animal vectors Insects – mosquitoes, fleas, lice, ticks Insects – mosquitoes, fleas, lice, ticks Mammals – rabies in wild animals, carriers of fleas, ticks Mammals – rabies in wild animals, carriers of fleas, ticks Birds – harbor some diseases that can be spread by insects – West Nile, etc. Birds – harbor some diseases that can be spread by insects – West Nile, etc.

Unit 11 Notes9 Fighting Infectious Disease Antibiotics – kill bacteria without harming cells of host Antibiotics – kill bacteria without harming cells of host Many produced naturally by living organisms (molds & fungi) Many produced naturally by living organisms (molds & fungi) Some are synthetic (man made) Some are synthetic (man made) Do not affect viruses Do not affect viruses Antiviral drugs Antiviral drugs Inhibit ability to invade cells & multiply Inhibit ability to invade cells & multiply Over the counter drugs Over the counter drugs Treat symptoms – cough, congestion, fever Treat symptoms – cough, congestion, fever Help you feel better, but do not treat infection Help you feel better, but do not treat infection