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Lecture 7

ANT C68 Lecture 7.docx

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University of Toronto St. George
Bianca Dahl

ANT C68 Lecture 7: Feb 28, 2013 Vaccines, Smallpox, Influenza Smallpox • Earliest recovered evidence: rash on mummified remains of Ramses V in Egypt (3,000 years old) • Caused 300-500 million deaths during 20 centuryth • A VIRUS from the genus Orthopoxvirus • 2 types: i. Variola major – causes most severe and lethal cases, case fatality rate 25%, up to 50% in virgin soil populations ii. Variola minor – milder infection, CFR less than 1% • Incubation period = 12 days. During this time individual is NOT infectious (able to transmit disease to others) • Then prodromal stage, pre-eruptive. 2-4 days. Still non-infectious. • Then first visible lesions, rash. 1-2 days *at this point lesions burst and enter saliva for respiratory transmission • Then pustules form, 7-10 days to reach maximum size. Also: fever, muscle pain, malaise, headache, nausea, vomiting • Pustules turn into scabs 16-20 days after first rash • No natural immunity • Survivors immune for life (active immunity: immunity from own body’s defenses from contact with a disease or a vaccine) • Survivors often disfigured, scarred. Possible blindness from corneal lesions. • In temperate areas epidemics are seasonal. Peaks in winter and spring. Smallpox Deities • Deities are a spiritual defense against disease • Allows people to put chaos of epidemics into natural order • All religions of Old World have a smallpox deity • Sitala = Indian god of smallpox. Both cause and cure (feared and loved) • She holds a broom to spread disease and a pot of cool water • Sitala: seen as an angry, unpredictable mother. Honoured with pilgrimages, shrines, ceremonies • Heat/cold essential to understanding of health • Hot = fever, associated with disease • Cool = treatment. Appeasement gestures include cool water, fragrant baths • Other deities: Chinese goddess of smallpox, pustules = called “beautiful flowers” so as not to offend • What happened once smallpox was eradicated? • Sitala’s other qualities took on significance: goddess of good fortune, protector of children. Also now associated with TB. Variolation • Originated in China • Deliberate infection from smallpox scabs from someone with an active case of smallpox • Scabs crushed into power and blown into recipient’s nose • Recipient develops mild form of fever and recovers • Not completely effective: 1-2% of people variolated still died (but far less than without variolation) • Spread to Europe: preferred to spread through skin puncture Edward Jenner • Noticed that milkmaids who had been infected with cowpox did not get smallpox (because cowpox causes immunity) • In 1796 he introduced cowpox into the arm of his gardener’s son • Then tried to give the boy smallpox … and couldn’t. • He was not the first to discover it, but was first to scientifically demonstrate vaccination Vaccination • Vaccination is when an individual’s immune system is stimulated to develop immunity to a pathogen. • In variolation, a live, unattenuated (unweakened) version of smallpox was injected into an individual to achieve immunization (immunity) • In smallpox vaccination, a different but closely related virus was used to achieve immunity. In the case of smallpox, cowpox is similar enough that it confers cross-protection • After the cowpox experiment, people were innoculated with pus from a vaccinated individual. It was a weaker version of the virus and safer than variolation. (Fewer deaths, less contagion.) • Today vaccination, inoculation and immunization are pretty much used interchangeably. • Vaccination can occur through: • Inactivated pathogens • Attenuated (weakened) pathogens • Virus-like particles • They only need to stimulate the body’s natural immune response so the body can make an its own antibodies (proteins that recognize and fight foreign agents in the body) • An antigen is anything that provokes an immune response in the body >For exam: Know difference between vaccination, immunization, and inoculation > Know Antibody and antigen difference Factors that make Smallpox Vaccine Effective • Only found in humans (no animal reservoir) • No asymptomatic carriers • Transmission only occurs during most obvious stage of symptoms (rash) • Survivors immune for life • Vaccination confers full immunity (although effectiveness decreases slightly over time) Vaccination • Became popular quite quickly after Jenner demonstrated his process • Smallpox vaccination provides immunity, although protection decreases over time • 1/1000 people develop non-life-threatening complications • 1-2/million people develop life-threatening complications (probably th worse in the 19 century) • Can’t unknowingly give smallpox (???) • MOVIE: The End of Smallpox • Know what “Bring Back Vaccination” -> KNOW FOR EXAM Anti-Vaccination Movements • In 1840, the British Government passed the Vaccination Act which provided free vaccines for the poor, outlawed variolation • 1853: vaccines compulsory for all infants during 1 three months. • Non-complying parents face fine or imprisonment • Almost immediate backlash, formation of Anti-Vaccination League (AVL) • AVL argued that their civil liberties were being violated • There were riots, demonstrations • In some areas, vaccine coverage plummeted • Usually followed by a smallpox epidemic • In 1898 British government developed concept of “conscientious objector” where parents could avoid vaccination on moral/religious grounds • Why did so many people resist vaccination? • Harmful side effects (syphilis, other diseases) • State interfering with parenting choices • Fear of animal virus (seen as evil) • Those who could afford it went to medical practitioners. Rest had to go to public houses: unsanitary, crowded. Put middle class workers in contact with poor. Stigmatizing. • Same sorts of arguments used against vaccines today • Vaccines unsafe, ineffective, cause idiopathic illnesses (autism, ADHD) • Diseases are trivial • Only provide temporary immunity • Vaccines enforced by drug companies for profit • Violation of civil liberties • Diseases decreasing anyway • Religious objections (vaccines immoral, involve experimenting on children) • Conspiracy theories (fear-mongering, control from government) • Alternative medicine equally effective • Some people should not have vaccines: immuno-compromised, egg allergies, organ transplants) Herd Immunity • Vaccination relies on herd immunity: as long as MOST people in a population are immune it will break the chain of transmission and provide protection even for people without immunity • Usually requires at least 90% coverage • Despite objections to smallpox vaccines, most people were vaccinated and prevalence decreased (probably due to herd immunity) Smallpox Eradication • WHO made big push to eradicate smallpox (because of unique features that made this possible) • Last case: October 26, 1977 in Somalia VIDEO: RX for Survival, “The End of Smallpox” Part I: The Campaign Begins (Nigeria) 1. How did they deal with low vaccine supply? 2. What is ring vaccination? Ring vaccination controls an outbreak by vaccinating and monitoring a ring of people around each infected individual. The idea is to form a buffer of immune individuals to prevent the spread of the disease 3. How did they identify cases? Part II: The Last Case (India) 1. How did they find cases? 2. How did they locate remote farmers? • • Two final cases, one death in 1978 in England (lab workers) • Today, smallpox held in TWO places: • Centre for Disease Control, Atlanta, Georgia, USA • State Research Centre of Virology and Biotechnology, Koltsovo, Russia Eradication of Other Diseases • Rinderpest: only other eradicated disease (occurs in cattle) • Next up for WHO: • Dracunculiasis: Guinea Worm • Easy to identify • effective control measures • no animal reservoir • Down to 4 countries, 1058 cases in 2012 • Polio • Effective, cheap vaccine • 223 cases worldwide in 2012, only endemic in three countries Smallpox Viral Supplies • There are TWO holding sites that we know of, but smallpox could potentially exist in other labs either accidentally or deliberately • Also possible re-infection from buried corpses, historical samples (ex. Scabs found in the back of a book) • Now that smallpox has been genetically sequenced, debate about whether we should destroy remaining supplies (debate still ongoing … stockpiles still exist) • PRO: destroying two remaining smallpox supplies would send message to anyone else concealing stocks that it is a hostile action • CON: virus may still exist, bioterrorism threat Continued: destroy remaining supplies? • CON: knowing genetic sequence does not tell us how virus acts in body (ex how it bypasses cellular defenses) • PRO: experimentation on smallpox might create “viral chimera” (new, highly lethal recombinant strain not seen in nature) • CON: if virus is accidentally released from burials, etc. then we wouldn’t have strain ready • CON: our technology changes over time. What we might learn from actual virus could change. • CON: cost of maintaining smallpox when money could be used to research other more pressing diseases Influenza • Very old: Hippocrates described 2,500 years ago (at least) • A VIRUS from family Orthomyxoviridae • Causes fever, sore throat, muscle pain, headache, cough, weakness • Potential complication: pneumonia • Normal seasonal CFR about 0.1%, mainly in elderly • Spread via respiratory transmission, contact with nasal secretions, infected fomites • Symptoms occur 1-2 days after infection. Able to transmit before symptoms appear. • Seasonal epidemics (peak in winter): indoors, drier air, holiday travel, virus survives longer in colder temp • Treatment: anti-viral medication (ex. Tamiflu) • An RNA virus, which means it makes more mistakes when it replicates. • Three types: • Influenza A: wild birds are natural host. Most virulent for h
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