Anthropology Plagues and People 2240 UofM

What are some anthropological elements to the study of infectious disease?

-Case Study Approach

- Holistic: Biological, social/cultural, environmental conditions

- Comparative: Cross Cultural (synchronic) and over time (diachronic) looking at populations to compare them

-Evolutionary: relationship between humans and microbes

Evolutionary Perspectives

-Hunting and Gathering

-Domestication and Sedentism

Hunting and Gathering

Constituted most of early humans lifestyles, focus on movement and finding food resources

Domestication and Sedentism

A turning point at about 12.5 kya (beginning of Neolithic) when people turned from a hunting and gathering lifestyle to domesticating plants (agriculture) and animals for food. Not all populations did this.

Comparing Hunting/Gathering to Domestication

Overall: agriculture produces a surplus, but it increased food insecurity (droughts affecting growth) and the decline in quality of diet. They didn't reach the heights of the foragers and had more stressors.

Fertility and microbes in hunting/gathering and domestication

Fertility increased among domesticated societies and population size increased because people were more sessile and could afford to have many children in a short period of time. Microbes thrive in larger populations like this, foragers only dealt with smaller diseases like worm infestations.

Villages evolved into towns which evolved into urban centers (Egypt).

Impacts of domestication

'My land' concept of people owning land and controlling boundaries which led to conflict and warfare

- Environmental degradation (compromising the land with irrigation and things stopped growing)

-Increase in socioeconomic stratification, 'law and order', people doing jobs they don't want to do which led to inequalities. In early agricultural communities they had to create law because of this.

An Increase in Infectious Disease Burdens in sessile communities, what happened?

-Lack of waste disposal, laws had to be made so you couldn't jus dump waste anywhere

-Insect and Animal pests thrived because there was food always near by (mice especially, cockroaches, flies) led to the domestication of cats

-High Population Density (overcrowding) facilitates the movement of pathogens

-Inability to 'just leave', you were invested in your land

Plagues Definition

Disease caused by a microorganism or pathogens, not all microbes are pathogens. Not all are 'bad' from a health standpoint (probiotics, E. coli) in digestive tract and skin

Disease Causing Microbes

Bacteria - small and simple in structure (single cell prokaryote - no cell nucleus) humans have eukaryotic cells They are everywhere - "niches in nature", reproduce rapidly, exchange useful genes efficiently, highly adaptable (antibiotic resistant genes, evade host defenses)

Viruses - acellular, one or more molecules or DNA or RNA in a protein coat. Inability to reproduce independently - depend on host relationships

Important developments in the understanding of Microbes

ALJIR

Antony Van Leeuwenhoek

Louis Pasteur

Joseph Lister

Ignacio Semmelweis

Robert Koch

Antony Van Leeuwenhoek (1632-1723)

Dutch, spare time grinding lenses to make simple microscopes , sketched observations of bacteria, Protozoa, spermatozoa and Red blood cells

- He did not share his grinding secrets but by mid 19th century microscopes were nbd

Important developments (1850-1910) The Golden Age of Bacteriology

"Scientific Giants" Pasteur, Koch and Lister

-Along with anatomy, pathology would fuel 'traditional' to 'modern' medicine transition ("scientific medicine", "biomedicine") late 1800's into early 1900's

Louis Pasteur (1822-1895)

French Chemist, "Father of Modern Microbiology"

-Yeast = conduit for fermentation; microbes could spoil food and wine

-Heating to destroy (or attenuate) unwanted microbes

-Contributed to the developing 'germ theory of disease' from sour wine when sick cattle and humans

Joseph Lister (1827-1912)

English surgeon in Glasgow, knew of Pasteurs work

-Mortality among amputees, considers role of microbes in post op infections

-Advocates use of carbolic acid

-"Father of Antiseptic Surgery"

-Asepsis/"listerism" improved survival of patients

Other Hospital based observations and Developments

Ignacio Semmelweis (obstetrician, Vienna)

-General hospital, risk of perpetual fever among women who had just given birth

-Dr's vs. midwives assisting at births, Dr.'s were spreading microbes from patients to mothers, midwives were more sterile

hand washing concept between patients to prevent the spread of microbes

Robert Koch

-German Physician

-Kochs postulates - established protocol to show conclusively that specific microbes cause specific diseases

-slides, staining, culturing bacteria

first researcher to view tuberculosis

Deaths due to infectious diseases (in western populations) Pros

Decreased rapidly in importance throughout the late 19th century

-improved living conditions

-health improvements (nutrition)

-Discovery of chemotherapy (drug treatments [antibiotics not cancer] )

-Reduced virulence (potential to cause disease) of the microbes themselves (disease had less virulence [ex scarlet fever] in 1900's)

-Vaccination and the idea of vaccinations helping to reduce mortality rate of infectious disease

Why are new infectious diseases emerging and and 'old' infectious diseases re-emerging?

The relationship between humans and microbes is forever evolving.

Global Travel: (we move humans efficiently) between populations introducing microbes to different populations

-Globalization: processing and supply of foodstuffs (condition under which food is grown; infected animals spread disease) water used to grow plants

Why are diseases re emerging? (Large Scale population movements)

Wars, famines, natural and human made disasters along with habitat modification of disease carrying insects and animals (deforestation, reforestation, irrigation, damns)

Why are diseases re emerging? (Social Inequalities)

Nutrition, medical care, housing. Privileged vs. Poor, makes them vulnerable to different diseases, poverty eats away at overall health (Tuberculosis on Native Reserves)

Why are diseases re emerging? (Human behavior and Resistance)

Drug use, unprotected sex (individual level, may increase or decrease someone's likelihood to be at an advantage or disadvantage)

Resistance due to increased improper use of antimicrobial agents and pesticides (resistant microbes, drug becomes less affective)

Increased human contact with 'new' microbe reservoirs (adventure level - regain forests, wilderness)

Why are diseases re emerging? (Synergies and Syndemic perspective)

Synergies in the disease environment (measles & Tuberculosis and HIV/AIDS and Tuberculosis)

People who already experienced the measles would suffer a vitamin A deficiency and would increase the risk of TB, TB would colonize in the respiratory tract due to at-risk epithelial cells - vaccinations helped with this

Syndemic perspective (Singer & Clair, 2003) have a broad perspective and look at all diseases that are in a population and that are in social stratifications [rich vs. poor] (Ex. Diabetes increases risk of TB), new synergies are emerging biological and social

What are two ways an infection can be expressed in an individual?

Overt and Silent

Overt

Causing a recognizable disease (ex. Chickenpox)

Infected individuals who can pass on the infection to others are considered 'infectious'

Silent

Individual has subclinical disease or as asymptomatic and unaffected (child who looks as if they barely have chickenpox, but they are 'infectious' and 'carriers'

Salmonella Typhi - bacterium that is in food, water and asymptomatic carriers; results in prolonged fever and diarrhea

(Mary Mallon - Typhoid Mary, cooked for wealthy families and got them all sick, they left her to die on an island alone)

Two ways an individual may experience an infection

Acute & chronic

Acute infection

Short lived (influenza)

Chronic Infection

Long standing infection

Two types of Chronic Infection

Active - person may be persistently infectious, may or may not be continually infectious (people would get Tuberculosis when they were a kid and now have a longstanding infection)

Latent - persistent but 'quiescent' infection which can recur. Pathogen resides in the body, and re-emerges (Chickenpox that turns to shingles later in life)

Two ways a population may experience infection

Epidemic & Endemic

Endemic

Disease which occurs regularly, at low or moderate frequency

Long term presence in a community or area

Epidemic

Sudden increases in disease frequency above endemic levels ('crisis mortality')

-Crisis mortality: spike in mortality rate where death rate increases to a notable level

- Disease is not continually present, but has been introduced from the outside (people are not used to the new pathogen)

A global epidemic is considered what type of infection?

A pandemic infection

What is herd immunity?

Collective resistance of a population to infection and spread of an infectious disease

-Can be high or low, usually low during an epidemic

-The higher the proportion of immune, the less likely is contact between infectious and susceptible individuals

-Herd immunity is not a consistent phenomenon, migration, immigration and emigration is responsible for this as well as children who are born into the population

Why do we need vaccinations every year?

Changes in BOTH human and microbial populations (viruses undergo antigenic drift/shift) can change herd immunity

Ex. The influenza strain changes every year

Hosts

If the host has experienced a pathogen before, immune response should be more effective

-The state of the body prior to the pathogen determines how well they body will fight it off

-Age; young (naive immune system) or old (breaking down immune system)

How do children/infants gain immunity?

Mothers pass down their immunity through breastmilk but the immune systems still have to grow and develop their own defenses

Genetics Example of host defenses

Th1 - (intracellular [macrophages] ) things that move into cells of the body

Vs.

Th2 - (humoral [antibodies] )

genes can potentially influence which system you are better at using

How are Pathogens affected in an environment?

Susceptibility to antibiotics

-ability to survive outside a host

-ability to produce toxins (reduce host immunity, destroy Iron and RBC's)

What does Streptococci do to Iron and RBC's? How does the body react?

It uses toxins to destroy Red Blood Cells so they can use up the iron contained inside. The human immune system will readjust and go anemic to deny the bacteria access to the Red blood cells

'Ecology' broadly defined

Physical environment (climate, rainfall, industrialization [*air quality/coal 'workhorse') can affect our ability to deal with pathogens

- Socio-economic Factors(nutrition, living conditions, etc)

- Gender and gender roles (Ex. Women preparing dead bodied [spread of disease i.e. Ebola] , men only in coal mines which leads to reduced lung function and risk of Tuberculosis)

Vectors and pathogens, examples

Some pathogens reply on vectors to access human hosts (mosquitos, ticks etc)

The social Impact of Plagues on Human Societies

-Isolation

-Scapegoating

-Fear and Hatred

-Reorganization

-Self-reflection

-Loss of Cultural Identity

When diseases hit a population they either bring out the best in the population or the worst

What are the 3 main routes of transmission of microbes

Contact, Vehicle & Vector

What are the 3 possibilities of Contact?

1) Direct Contact

2) Droplet Transmission

3) Indirect Contact, via Fomites

Direct Contact

Person to person, physical contact

- 'barrier' methods typically employed to prevent transmission (gloves, condoms)

Droplet Transmission

Especially relevant to respiratory diseases

-Includes coughs, sneezes, spit

-No further than 1 meter distance from the source: proximity is important

Indirect Contact &

(White coat example)

Via Fomites (ex. Doorknob)

-inanimate objects which can be contaminated by an infectious person

-white coat being banned in UK because it can be a carrier of pathogens/contamination from patient to patient.

Vehicle transmission & 3 mediums, what helps stop transmission?

Via an inanimate medium

-Air, Food & Liquid

-Airbourne; spread by rocket nuclei they are so light that they float on particles, travels 1 meter

-Nature of vehicle can have important implications for scope transmission (contaminated food or weather can reach many people)

-UV lighting in hospitals can help stop transmission

Vehicle

Living transmitters of infection (insects like mosquitos, vertebrates like bats)

Vectors may be involved in

Biological transmission (development, inside the vector EX. Fleas)

Or

Harborage transmission (carriage only, on its body EX. Flies with bacteria on there sticky legs)

The Human Body; two defenses

Skin - Protective when unbroken.

Fatty acids in skin oil (inhibit pathogen growth)

Surface/Normal Flora (inhibit pathogen growth)

Sweat and perspiration contains lysozyme (breaks down bacterial cell walls)

Digestive Tract

Mucus Membrane (physical barrier, bacteria cannot colonize)

Stomach Acids

Liver enzymes counteract toxins

Normal Flora

Normal Flora, what does it do?

Oliver 2003

The stomach acid and pH and generally 'inhospitable' for normal flora but some pathogens can withstand it

-The Small intestine: fast flow rate (3-5 hours) very busy, too fast to allow colonization of normal flora

-The Colon: much slower (24-48 hours), resident microbes break down undigestible polysaccharides, especially in areas of low food supply

normal flora = selective advantage

Portals of Entry for pathogens on humans

- Inhalation

- Ingestion

- Person to person, through direct contact and exchanges

- Penetration of the skin (injuries, insect bites, animal bites, needles)

Portals of Exit for pathogens on humans

-Mouth (saliva, sputum, vomit)

-Eyes (tears, exudate)

-Body Surfaces (skin, crusts, exudate)

-Punctures (blood)

-Urogenital (urine, blood, secretions, semen, placental)

-Anus (poop) 💩

Initial Symptoms of infection

Product of the infecting microbe and/or the efforts of the immune system

Vague or non-specific: fever [37degrees c] Carl Wunderlich

-Variation in body temperature in order to try kill pathogens, humans try to stop spiking of body temp, when body temp is high the pathogens need more iron but the body hides it. Theses are defense mechanisms (Adapted Response)

-Muscle aches, malaise, skin rashes, inflammation

Elements of the Immune Response; two types of Immunity

All deriving from bone marrow (immune related cells in bone marrow)

Innate Immunity - Always present, immediate response, lower potency: physical (skin) barrier, phagocytes and macrophages

Adaptive Immunity - Typically silent, 1-2 weeks response, more potent

Two types of immunity within Adaptive Immunity (H & C)

Humoral Immunity (B cells and antibodies), identifying foreign antigens, occurs in bloodstream of various liquids

Cell Mediated Immune response (T cells and cytokines - protein signals), within cells themselves

Host Resistance, Two immunities and a way to create immunity

Passive Immunity

Acquired Immunity

Active Immunization

Passive Immunity

Resistance via Mothers immune system

-Transfer of immune cells (ex. Antibodies) via the placenta to fetus

-Once born, through breastmilk

Acquired Immunity

develops in an individuals lifetime

- Immunity is acquired by virtue of a history of previous exposure to a pathogen (works well when pathogen is unchanged)

- May need repeated exposures to keep immunity bolstered (chicken pox, since there is a decline because of vaccinations, our bodies are more susceptible to a breakout because we no longer bump into the chickenpox [why we need a shingles vaccination] )

Active Immunization

Selectively priming (awakening, sensitizing) the immune system to pathogens

-Immediate recognition of pathogens 'biological signature'

-Increased likelihood of mounting a quick and effective immune response

-Mass vaccination = High herd immunity

contemporary western medical practice vaccinates for diphtheria, Pertussis, Tetanus and Polio (dTAP)

Diphtheria (Corynebacterium diptheriae)

Caused by a toxin-producing bacterium

-Spread via contact transmission (direct, indirect, droplet)

-Common complication of respiratory infection: Difficulty breathing

Adheres to membrane or tonsils, pharynx, nose that compromises your ability to breath

"Child killer"

Diphtheria Control , who's at risk? When were vaccinations brought in? What animal was used to create the vaccination?

When endemic: children at greatest risk between 1-5

-1890's antitoxins injected (most celebrated treatments for a disease, hope & confidence)

-1920's/30's vaccination in US and Canada (herd immunity caused it to lose its grip on the population)

antitoxin came from horses, they were injected and their immune systems provided antibodies, which was then refined into a serum

Epidemic Outbreaks of Diphtheria in industrialized countries

Russia in 1990's had the biggest outbreak since the 60's

1992: 4000 cases (compared to 4 in the US)

1995: over 50,000 cases

Why did the outbreak of Diphtheria occur in Russia?

1987: massive restructuring of the soviet economy (Gorbachev & "Perestroika")

Aim for decentralization/greater individualism: towards capitalism, more households with great health & some in poor conditions

PROBLEM: Collapse of centralized healthcare (no vaccination programs), Worsening socioeconomic conditions

1996: vaccination campaign

Same political economic forced affecting increases in other diseases (Tuberculosis & Typhoid Fever)

Innovations in the rise of scientific medicine (biomedicine)

1796: Edward Jenner - affected the approach of inoculation of small pox (Medical Therapeutics: Antibiotics)

Penicillin: 1945, Fleming, Chain and Floery

-Mould (airborne) Penicillium notatum

-antimicrobial, provides proof some microbes can be bad for one another

-Targets bacterial cell wall

-Penicillin resistant bacteria have been selected for (synthesize penicillinase)

Streptomycin: 1943, Albert Schatz, Selma Waksman.

-Inspired by Flemings findings

-Antibacterial properties of soil microbes Streptopmyces griseus

Measuring Disease Affects (I,P,V)

Infectivity - The proportion of exposed people who become infected

Pathogenicity - The proportion of infected people who proceed to clinical disease state

Virulence - The proportion of the persons with clinical disease who become severely ill or die

Mortality Rate

Number of deaths due to infectious disease/the total number of people in the population (to total n exposed)

-Can specialize (ex. Infant mortality rate - those under 1)

-Morbidity rate (sickness)

Fox's Generalizations

Historical perspective, can still be applied today

-At beginning of epidemics many people have underestimate the severity of the problem

-Considerable fear and anxiety has accompanied the perception that the epidemic was gaining strength

-Responses to fear include flight, denial and scapegoating of alleged carriers

-Efforts to quarantine and isolate have been ineffective in limiting the spread of an epidemic

-After a period of denial or panic, rational policies are established, almost always by a coalition of business and government leaders, with support from prominent members of the medical profession

Fox's Generalizations Examples

Emergency departments in Toronto during the outbreak of SARS, no visitors, isolation of patients

-In most outbreaks there's shortages of nurses and doctors to treat the sick unless incentives are given people wont help

-epidemics are always expensive Directly (treatment) and indirectly (productivity losses).

Ex. Avril Lavigne concert in Toronto 2003 suffered financially because of SARS

Yellow Fever

Belongs to the family Flaviviridae (arthropod vectors: mosquitos & ticks)

Of the genus Flavivirus (YFV, Dengua, West Nile; can affect animals and humans)

-Virus must be in a host (living) cells to grow/replicate, otherwise - RNA in a protein coat

Yellow Fever Infection

mosquito-borne viral hepatitis

-Affects your liver function

-Results in high levels of viremia (virus carried in blood)

-Requirement of insect (mosquito) vector-borne diseases

Yellow Fever Symptoms

3-6 Days after infection = incubation period, virus remains silent

Can then proceed to:

1) no symptoms, no disease emerges

2) Acute Phase: fever, headache, vomiting; persists 3-4 days and either improves or 15% on to:

Toxic Phase: compromised liver & kidney function, liver is unable to provide blood clotting factors, bleeding from mouth, eyes, stomach, poop.

Black coffee ground vomit

Jaundice (bilirubin/hemoglobin metabolism)

Yellow Fever Distribution

Historically in Tropical/Subtropical areas: Africa, the Americas, Distribution of diseases are not consistent in outbreaks

-Currently: Tropical areas of Africa an the Americas, several Caribbean Islands

- Estimates 200,000 cases and (30,000 deaths) per year, economics are important in stopping it (LDC's suffer more than MDC's)

Yellow Fever Transmission

Hosts are humans and primates (great apes/monkeys)

- Moves from host to host via biting mosquito (vector) [horizontal transmission]

- Mosquito is able to pass infection via infected eggs to its offspring (hatch with rainy season) [vertical transmission], this makes controlling the disease extremely hard, even is mosquitos are gone, eggs remain

- Mosquito = TRUE reservoir , ensuring virus survival from year to year

3 Transmission Cycles of Yellow Fever (S, I, U)

Sylvatic, Intermediate, urban

Sylvatic Yellow Fever

Jungle Yellow Fever

-Occurs deep in tropical rainforests, affects mostly great apes and monkeys

-Humans may attain this type if they assert themselves into rainforests (ex. Travel)

Intermediate Yellow Fever

Transitional zones

-Humans build on new land and encroach on tropical rainforests, this creates the possibility of humans and primates sharing the same virus

Urban Yellow Fever

No primates involved

-Humans and Urban Mosquitos; aided in high population densities

-San Jose, Costa Rica and the virus

To avoid an epidemic from occurring, what must happen?

80% of the population must have an immunity to the YFV, this can occur by:

-Prior exposure to Yellow Fever

-Vaccination programs (childhood in endemic countries)

-Spraying to kill mosquitos during endemics allows for vaccination of group at risk.. BUT

-Must recognize early cases (can be confused with malaria)

Maintaining Control of Yellow Fever Example

Costa Rica: requires proof of immunization of those coming from South America and Sub-Saharan Africa to Costa Rica. (They could be hosts)

Current Problems with YFV

Yellow Fever epidemics are increasing

-The problem is that mosquito habitats and populations expanding (deforestation & urbanization)

-Many susceptible unvaccinated populations

Who was the physician from Havana that insisted Mosquitos were critical in yellow fever transmission

Carlos J Finlay

What did Walter Reed do to his soldiers?

Major in the US Army Medical Corps, Experimented on soldiers against their will (ethical problems)

Why was the US Army concerned with the Panama Canal

They were concerned about the transmission of Yellow Fever, During the construction in 1880-1914, Thousands of workers died due to Yellow Fever and Malaria.

The intention of the Canal was to join the Atlantic and Pacific for trade/navy

Yellow Fever Milestones

1901 - Transmission via mosquito vector

1927 - Yellow fever virus isolated (microscopy)

1936 - Vaccination

Aedes aegypti

highly adaptable as an "urban mosquito" (synanthropic able to adapt and live with human populations, and anthroophilic it prefers to feed on humans and primates)

- Only females bite to feed their eggs

- Prefers small bodies of clean, still water (barrels, water tanks, tires)

- Not a strong flier (~few hundred meters) benefits from living in crowded areas

- Daytime biters especially at dawn and dusk, bed nets are not helpful

- First heavy rains wakes up dormant eggs

The perfect urban mosquito life

Warm temperature = more bloodmeals

Clean water for breeding

No Predators

Humans for biting

Direct control measures

Larvicide/Insecticide

Eliminate/Oil standing water

"Top down"/community based (everyone in community expects government to wholly responsible for mosquitoes, but people need to take initiative and help reduce populations

Reducing human contact with mosquitoes - How do we do this in the modern world

Screens on windows

Mosquito repellant

Protective clothing

1804 Gibraltar Case Study

Was a military/naval post under British rule that controlled traffic that comes through them Mediterranean to the Atlantic.

-British colony in 1830

-Had no means of growing food because it was mostly rock

Living Conditions in Gibraltar early 19th century, trade, class ect

Depended on good relations with Spain and Morocco for food

-inadequate sewer and sanitation systems

-Social class structure was ruled by the British Military Governor, followed by Colonial admin, military population, civil population & 'floating' population, had a convict station

Non contagionists

Believed smells could make you sick, so in Gibraltar they would shoot off cannons to get the gunpowder smell and have bonfires to 'purify' the air

Gibraltarian Population (civilian)

Fusion population consisting of Europeans, North African and Mediterranean people

- "motley" population including "seedy adventurers" & fortune hunters

- Naval Port and garrison

- All features enhancing introduction and transmission of disease

Long distance communication (vie trade, colonialism, military activity) facilitating movement of peoples & disease, Gibraltar was connected with diverse places including the New Americas (new world)

Since Yellow Fever was not endemic in Spain, how/why was Yellow Fever periodically introduced?

Cuba was an important reason in why yellow fever travelled to Spain, the cargo ships full of of clean water and food was a perfect place for the physical connection between the old world and new world, the mosquitos were imported with the movement of goods

How did authorities suspect yellow fever entered Gibraltar in 1804?

Santo a shopkeeper had come to Gibraltar before they severed the land crossing connection to Spain, Santo was ill when he entered and mosquitos spread his disease around to his neighbors. He potentially introduced Yellow Fever into the population

Was the arrival of Santo enough to start an epidemic?

Gibraltar had the key ingredients to to cause an epidemic:

Mosquito, susceptible people, the pathogen and infected individuals

Aedes aegypti Origins

Aedes aegypti has African origins, it moved with the human origins and travel. It now has a worldwide spread because they are so adaptable, but are not in Canada

Asia does have the mosquito but never any YF epidemics

Movement of vectors and viruses of the Yellow fever virus

Linkage between Africa and the Americas in colonial slave trade

-The mosquitos on ships survived by living in barrels full of drinking water, and bilge water that collects at the bottom of the ship. It was salty but the mosquito tolerates it so long as it is not too high in salt [ ]

-First estimate in Sylvatic cycles (with indigenous 'forest mosquitos' ex. Genus Haemagogus)

Aedes Aegypti Distribution