Infectious Diseases

1. Infectious Diseases

2. Pathogens • Several types of small microscopic organisms • Most are Parasites – organisms that live in or on another organism and derive nourishment from it • Forms – bacteria, viruses, rickettsias, protozoans, and fungi

3. Bacteria • Single-celled microorganism • Live anywhere – air, soil, and water • Some are harmful to humans and some are good • When enter the body they multiply at a rapid rate • If person is not immune – disease results

4. Virus • Smallest known type of infectious agent • One of our worst enemies • Not living cells • Entirely dependent on living cells for survival • Only attack specific types of cells – called a host

5. Rickettsias • Resemble small bacteria but like viruses only able to multiply by invading a cell • Found in intestinal tracts of insects – fleas • Passed by bites or feces deposited on the skin • Typhus or rocky Mt. spotted fever

6. Protozoans • Single celled organisms larger than bacteria with a complex structure • Most are harmless • Common in tropical areas with poor sanitation

7. Fungi • Simple organisms that cannot make their own food • Prefer dark, damp environments – nails, hair, and skin • Ringworm and athlete’s foot

8. Direct contact • When an uninfected person comes in physical contact with an infected person • STD’s • Bite • Pregnant mother to unborn child

9. Indirect contact • Enter the body through the lungs • exhaled, coughed, or sneezed out by infectious person • Inhaled and entered through eyes or nose

10. Animals or insects • Infected dogs or other animals can spread diseases – rabies • Mosquitoes or other bloodsucking insect can spread pathogens from an infected person to a uninfected person – malaria

11. Contaminated Objects • Pathogens are spread by objects an uninfected person may touch – eating utensils, glasses, toothbrush, hairbrush, or needles

12. Environment • Food – careless handling can lead to food poisoning • Water and soil – careless disposal of infectious waste – toxic dumping – can be deadly • Air – toxic chemicals released from factories

13. Immune Response • Two main types of defenses • Innate immune system – inborn defenses – provides nonspecific resistance • Adaptive immune system – specific resistance • Both work together to protect against pathogens

14. Nonspecific resistance • Physical barriers – first line of defense • Main barrier is your skin • Mucus membranes – the soft, skinlike lining of many parts of the body – mouth, nose, and bronchial tubes produce mucus to trap pathogens

15. Chemical barriers – enzymes in tears and saliva destroy pathogens • Acidic digestive juices of the stomach destroy pathogens swallowed with food • Other chemicals cause body changes to help cells fight pathogens

16. Body cells – When pathogens reach bloodsteam, certain types of white blood cells called phagocytes group together and destroy them

17. Inflammatory response – body goes into a “red alert” • Chemical mediators are released, blood vessels dilate and increase blood flow, this allows phagocytes to leave blood stream and enter body tissues. This continues until the pathogen is destroyed. • Symptoms – heat, redness, and swelling

18. Specific Resistance • General response – not always enough to protect you from disease • Lymphocytes – white blood cells that fight pathogens

19. B Cells – encounter a pathogen they enlarge and multiply – turn into plasma cells – produce antibodies – proteins that destroy or neutralize invading pathogens • Remain in blood to become active when encounters the pathogen again

20. T cells – two main groups – alerts B cells • Killer T cells – multiply by presence of abnormal body cells – attach to cells and release toxins to destroy abnormal cells • Helper T cells – aid the activity of the B and T cells.

21. Respiratory infections • Common Cold – viral • Symptoms – stuffy, runny nose, sneezing, sore throat, and headache • Contracted – breathing in contaminated droplets, rubbing eyes or nose

22. Influenza – viral • Symptoms – chills, fever, headache, muscle ache, and weakness • Contamination – droplet coughed or sneezed into the air • Flu can develop into pneumonia – serious inflammation of the lungs

23. Tuberculosis – bacterial • Infection that most often affects the lungs • Symptoms – coughing (sometime blood), chest pain, shortness of breath, fever, sweating, poor appetite, and weight loss • Contamination – airborn droplets from coughing or sneezing

24. Strep throat – bacterial • Infection of the throat • Symptoms – sore throat, fever, general feeling of illness, and enlarged lymph nodes in neck • Contamination – droplets coughed or breathed into the air

25. Immunity • Body’s natural resistance to many pathogens

26. Active immunity • Body develops to protect you from disease • Some last a life time and some a short period

27. Passive immunity • Temporary immunity that an infant acquires from its mother • Last for a few months until baby can produce antibodies on it own

28. Vaccination • Causing the body to produce antibodies against the pathogen • Live-virus vaccines – weak virus • Killed-virus vaccines – killed virus • Toxoids – chemically treated bacteria to stimulate production of antibodies for active immunity