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ANTC67 W 6.docx

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University of Toronto Scarborough
Larry Sawchuk

ANTC67 W6 - We don’t know how many people had influenza so you cannot compute some things - What it is, objective of assignment, how it fits into global picture of the study, etc. Midterm - All MC - The exam will be based on everything that he covered up til today - 60% comes from lecture and 40% from reading - Calculator - Chapter 1, 2, and 3, Tutorial 2 right article… - Dates and names – from the lecture yes but not really from the readings - Case control for this week is also covered - Tutorial will be on exam - About 70 questions of 4 choices - The class average will be 70. A dedicated place of isolation from the deadly yellow fever during the 1828 epidemic in Gibraltar was: A the hospital B the church C The neutral ground D The Spanish lines E The Bay - Neutal ground was a place of putrification – windy and no mosquitoes Lecture Plague elements: - Host o Exposure, Susceptibility, Immune Response  ability to leave (avoid)  living and working conditions  previous experience with the disease  state of the host body (nutrition, other diseases)  age and gender - Agent (disease-causing microbe) o Ability to survive outside a host o Ability to produce toxins (reduce host immunity, RBCs & iron) o Susceptibility to antibiotics - Vectors o Some microbes require a transmission agent to aid their access to a human host o Why is female mosquito so deadly? They want blood to feed offspring - Ecology o Physical (geology, climate) environment o Cultural, Social, Political factors (from last class, factors like wars & political unrest can lead to decay of social & medical infrastructure) o Socio-economic factors (e.g., poverty) How microbes are transmitted - There are 3 main routes of transmission: o Contact o Vehicle  Fomites  if I cough on this phone, some pathogen might be sitting on it and be contagious o Vector Contact  3 possibilities - Direct Contact o (e.g., person-to-person) o What do doctors usually give? Prescription. Even that prescription can be contaminating - Indirect Contact: via fomites: o Fomite: inanimate objects which can be contaminated by an infected person (a ‘chance’ phenomenon) - Droplet transmission o Esp relevant for respiratory diseases o Includes coughs, sneezes, spit o No further than 1 meter distance from source (otherwise = airborne): proximity important o Whenever you are in a club or concert, droplets of water is coming out of singers’ mouth. This is possibility of pathogen transmission. o You can use handkerchief but if I put it in the pocket and keep doing that it is contaminating o Airborne when sneezing Barrier methods - typically employed to prevent transmission - i.e. gloves, face masks, some kind of net to protect from mosquitoes, condom, etc. Vehicle Transmission  Via an inanimate medium:  Air, Food, Liquid (e.g., water)  Air-borne Spread by droplet nuclei (1-4 micrometers) – either as an aerosol or on a dust particle Travels over a meter or more  Nature of vehicle can have important implications for scope of transmission – e.g., contaminated food or water source may reach large number of people - Salmonella – from food poisoning from law or badly cooked food. - Vectors may be involved in biologic transmission or harborage… *** - Why is mosquito changing? Because it is having babies. Vector Transmission  Vector-borne Living transmitters of infection Can include arthropods (e.g., mosquito) or vertebrates (e.g., bat) Vectors may be involved in biologic transmission (internal) or harborage transmission (external) Body’s first line of defense  Mouth and Nose mucous membrane lining mouth and nose hairlike projections (cilia) mucous and saliva contain enzymes  Eyes eyelashes tears to wash the eyes tears contain lysozyme (an enzyme that attacks the cell walls of many bacteria) mucous membrane - inner eyelids/eyeballs  Skin protective when unbroken  dry and acidic  normal flora  sweat / perspiration contains lysozyme  fatty acids in skin oil  Digestive Tract mucous membrane lining  stomach acids  liver enzymes to counteract toxins  bile salts and alkaline nature of small intestine  normal flora…  Oliver (2003):  stomach – acidic pH ‘inhospitable’, but…  small intestine – flow rate (3-5 hours) too fast to allow for colonization (selective benefit – no competition for simple sugars & proteins)  colon – much slower (24-48 hours):  resident microbes play important role in breaking down undigestible polysaccharides which would otherwise be ‘unavailable’  in areas of low food supply = selective advantage)  Genital / Urinary Tract  urine flow  among females, acidic quality of the vagina  normal flora - Saliva - Nose – little hair in your nose (cilia***) - Enzyme – speed up process and breakdown certain micro - Eyelash – prevents dust pathogens to get in - Tears – washes away the junk that can be contaminated - Isozyme *** - Skin is an important barrier o There are little creatures Digestive tract - A lot of mucous - Stomach acids – Pattenkofer said one of the reason why he didn’t get cholera might be because he had acidic stomach - Bile salts and alkaline - But.. there are good thing and bad thing – it protects you in one thing but doesn’t to the other - Transit time o If you’re eating something, your body will utilize it and expel it. The transit time should be in harmony with you extracting material in timely fashion. What if the transit time is very slow. Say there is something that will sit in your stomach for a long time (constipation), then it can damage you in very slow transit time that will increase your expose to pathogen. - Different rates of metabolism / transit time - Genital urinary tract o Acidic and prevents disease Yet…despite these defenses… Humans can still be vulnerable to infection and play a role in spreading infection … Portals of Entry - Inhaled - Ingested - Person to person, through direct contact - Penetration of the skin (injuries, insect, animal bite, needles) Portals of exit - Mouth - saliva, sputum, vomit - Eyes - tears, exudate - Body surfaces - skin, crusts, exudate - Punctures - blood - Urogenital - urine, secretions, semen, placental - Anus – faeces - Pretty much the same as entry Sneezing  Mucous / Moisture droplets – the spray associated with a sneeze  Droplets are about 10 micrometers in size  Initial travelling time - 100 meters per second (200 miles per hour; 322 km per hour) So what happens if microbes gain admission… 1. The microbe may die 2. The microbe may survive without giving rise to disease; can cause a host immune reaction, reducing success of re-infection OR… 3. The microbe may survive and produce clinical disease - if fatal, both host and microbe die  however the **most successful pathogens** have evolved in favour of not killing their hosts  Especially applies to pathogens believed to have a long evolutionary history in association with humans  E.g., helminth (worm) infections, herpes virus - Antigen – if you have microorganism and it has sugar molecules which body will recognize. TB is covered of wax and there is nothing protruding from it. Every microorganism has potential for setting off alarm. - It is not in the best interest for microorganism to kill you. So from evolutionary perspective, they would want to stay in one’s body, but the others might want to kill the host. If they kill the host they have to find someone else. - Good disease allows them to survive, reproduce at sexual level. He is sick but not sick enough. More likely to not adapt that st
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