10.2.7 Intro to diseases + Cholera + STIs

• Pathogens


  Organisms that cause diseases
• Viruses also cause diseases but they are technically not organisms
• Infectious or transmissible diseases

  Diseases caused by pathogens such as bacteria, viruses and fungi that can be passed from person to person
• Ways pathogens can be passed from person to person

  • Direct contact (transfer of body fluids)
  • Indirect contact (droplets in air, contaminated food/water, touching contaminated surfaces, vector like mosquito)
• Preventing the spread of infectious diseases


  1. Prepare food hygienically/good personal hygiene (wash hands, wash utensils, wipe surfaces, refrigerate meat, cook meat thoroughly)

  2. Dispose of waste properly (wrap meat packages, separate recyclables from food residue)

  3. Clean water (treat sewage, supply clean water)
• Ways the body prevents the entry of pathogens


  • Skin
  • Hairs in nose
  • Ciliated cells and goblet cells in trachea
  • Stomach acid
• What happens if pathogens get in


  • They secrete poisons (toxins) which can make you feel sick, vomit, have diarrhea, have 'the chills'
  • They multiply, reproduce quickly, damage cells, use up compounds healthy cells should be using, viruses cause host cell to burst
  • They cause an immune response, more blood to affected area, swelling and inflammation
• Cholera


  Disease caused by bacterium Vibrio cholerae, spread mostly by contaminated water and food, humans are the only affected animal, risk factors include poor sanitation, lack of clean drinking water, poverty, main symptom is diarrhea

  
• How Vibrio cholerae causes diarrhea

  1. Vibrio cholerae releases toxins in small intestine

  2. Toxins bind to proteins on small intestine membrane

  3. Toxin causes chloride ions to move out from cell into lumen

  4. Reduced water potential in lumen causes water to move in by osmosis, leading to diarrhea and dehydration

  
• Examples of sexually transmitted infections (STIs)

  • Gonorrhea (caused by Neisseria gonorrhoeae)
  • Syphilis (caused by Treponema pallidum)
  • Chlamydia (caused by Chlamydia trachomatis)
  • HIV (caused by Human Immunodeficiency Virus, can lead to AIDS)
• STIs


  Can lack symptoms but can be treated with antibiotics, resistant strains are developing
• Reducing the spread of STIs

  1. Individually: Know partner's sexual history, use condom/femidom, have regular medical check-ups

  2. Worldwide: Education programmes, provide antibiotics, develop vaccines and antiviral drugs
• HIV


  An example of an STI, the virus that usually leads to the development of acquired immunodeficiency disease (AIDS)