DISEASE

1. DISEASE

2. What is disease? • A disease is an impairment that stops the body functioning as it should • Mostly there will be symptoms (e.g. headache and runny nose when you get the flu) • Sometimes there may be no symptoms the sufferer can feel for a long time (e.g. AIDS can lay dormant for many years before the sufferer becomes HIV positive and starts to suffer from the disease)

3. Disease Causes Non-infectious diseases • Genetic diseases are inherited from parents and passed down through their genes (e.g. Haemophilia, Cystic fibrosis) • Immunological diseases- result from malfunction of the body’s defence systems. Often there is a genetic component of this (e.g. if parents suffer asthma, eczema or allergies, it is more likely that their children will too) • Lifestyle diseases- result from the way we live (e.g. the foods we eat, our levels of physical activity etc) • Incorrect body function- e.g uncontrolled cell division in cancers. • Parasitic organisms- e.g. worms, head lice etc.

4. Infectious diseases • Infectious diseases are caused by microorganisms which can pass from one person to the next • Examples are: • Bacteria • Protozoans • Viruses • Fungi

5. Bacteria • Single celled, free living organisms • Different shapes: • Spirilla ( spiral shaped- e.g cholera) • Bacilli (rod shaped- e.g. bubonic plague) • Cocci (spherical- e.gtonsilitis) ..\..\..\..\..\Videos\bacteria classification.flv

6. What are bacteria? • A single cell with a circular loop of DNA • Have cell wall like plant cells but made of different materials • Bacteria multiply by replicating their DNA inside their cells then their cells split in two. This can happen over and over very rapidly • Some require oxygen but others survive without oxygen • ..\..\..\..\..\Videos\bacterial growth.flv

7. How do bacteria cause disease? • By being ingested (eaten), breathed in or through cuts in the skin • Once inside they invade the body and rapidly reproduce. They may destroy cells, or live and multiply in between cells in the body. • They cause various symptoms- often vomiting, diarrhoea and stomach pain if ingested into the digestive tract.

8. Treating bacterial diseases • Antibiotics are substances which kill bacteria or stop their growth • Penicillin is the most well-known antibiotic but there are many types • Some antibiotics come from fungi, others from bacteria themselves • Antibiotic resistance is an issue because bacteria reproduce so quickly. Strains that resist the antibiotic effects survive and then new antibiotics need to be found. • Also, vaccinations and antiserums can be used to protect against future attack (see further detail under viruses)

9. Viruses • Viruses need a host to reproduce • Many arguments as to whether they are dead or alive. • They exist in a crystalline form outside their host- some can live for centuries. • They need a suitable host to reproduce • They consist of genetic material surrounded by a protein coat

10. How do viruses cause infection? • Viruses are often passed through hand to hand contact, infected food, or bodily fluids • They are able to attach themselves to plant and animal cells. Each virus has specific host animals or plants which it can infect • Sometimes they are carried by a third party vector to the host (e.g. mosquito carrying Ross River fever virus)

11. How are viruses treated? • Antibiotics do not work on viruses- there is no point taking an antibiotic to cure a cold • One of the only ways to treat a virus is via a vaccination which consists of a weakened or disabled form of the virus. From there, the organism under attack can produce antibodies to fight the virus if it occurs later. • Another way is to inject antibodies, in a substance called antiserum.

12. Virus video ..\..\..\..\..\Videos\Virus complete.avi