HLTB21H3 Lecture Notes - Middle Ear

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14 Apr 2011
Lecture 1
Parasites: organism that grows, feeds, and is sheltered on or in a different
organism and that does not contribute to the survival of its host
Virus: ultimate micro-parasite, smaller than bacteria; neither cells not
organisms; can only reproduce within their host
Macroparasites: composed of many cells; does not multiply in host, instead cycles
through transmission stages–eggs and larvaewhich pass into the external
Transmission: the sending or passing of something, such as a message or disease
from one place or person to another
Incubation period: the interval of time required for development of a disease
Latent period: seemingly inactive period between exposure to an infection and
subsequent illness
Parasite virulence: capacity of a parasite to cause disease
Zoonotic infections: animal infections that can be transmitted to humans
What are the main factors that influence the occurrence of a disease?
Host: (usually a person) immunity, genetics, nutrition
Environment: some whether conditions dont allow for diseases to take place
Agent: biological, physical, chemical (type of bacteria)
Modes of Disease Transmission
Direct occurs through direct contact, e.g. from person to person
Indirect through a common route / vector, e.g. contaminated air / water,
Portal of entry: Dermal through the skin, e.g. fungi
Ingestion through the mouth, e.g. E.coli in water
Inhalation during respiration, e.g. particulate matter
Types of disease outbreaks
Three main types:
1) Endemic usual occurrence of a given disease within
a given geographical area 2) Epidemic occurrence
of a disease in excess of normal expectancy in a defined region 3)
Pandemic worldwide epidemic
Definition of Plagues
In the past, all disease outbreaks were referred to as plagues
Derived from Latin word plaga which means to strike a blow that wounds
Today, we refer to such a disease outbreak as an epidemic, comes from Greek
word epi’ (among) and demos (“the people”)
Acceptable definition of plague: highly infectious, usually fatal epidemic disease.
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Plague is a serious, potentially life-threatening infectious disease that is usually
transmitted to humans by the bites of rodent fleas
Historical Perspective
Hunter & Gather society:
-Society was a lot healthier because there was less contact with people
-Scarce population
- Hunters never stayed in the same place, they were constantly moving around
- Barely no diseases
Agriculture Revolution:
- People started settling down
- Had bigger families (more children= free labour)
- People began being more connected
- no bathrooms or hygiene resolutions
- Diseases started to increase e.g. Black Plaque
Globalized Societies:
-Better transportation such as airplanes, trains, cars helped increase diseases to
-Also helped increase transmission e.g. Sars
Technological Advancements:
Certain present day new products that are created may result in creating diseases.
e.g. Toxic Shock Syndrome
Plaques of Antiquity
oDates back from 5000 BC to 700 AD
oCharacterized by parasites with long lived transmission stages (e.g. eggs,
larva, ...)
oTransmitted from person to person contact.
The Pharaohs Plaque
Evidence that it dates back to 1900 BC
Thought to first have appeared in the Nile Valley of Egypt
Agriculture, the inundation of the Nile, eventually irrigation created favorable
conditions that promoted the spread of the disease
Disease now known as snail fever or blood fluke disease / endemic hematuria /
European invasion of Egypt (1799 1801) resulted in the first European
experience with plaques
The Plaque of Athens
Occurred in 430BC
an epidemic that started in Ethiopia and gradually moved into Egypt
raged for about two years
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identity of the disease is not known
characterized by fever, pustules and a rash of extremities
destroyed fighting power of the Athenian navy
The Roman Fever
Roman Empire was established 27 BC - it had a series of colonies
Vast trade network emerged
Malaria became prevalent
Thought to result from the bad air due to vapors released from marshes in the
Epidemics occurred every 5 to 8 years
Plague had an effect on the early Christian Church
The Antonine Plaque
AD 166 - brought to the Roman Empire by Roman troops from Mesopotamia
Made its way to Europe
Symptoms: high fever, inflammation of the mouth and throat, thirst, diarrhea,
postules that appeared after 9 days
Identity of the plague not known likely to be the first record of smallpox
The Cyprian Plaque
250 AD believed to have originated in Ethiopia, moved to Egypt, and made its
way to the Roman colonies of North Africa.
Justinian Plaque
First pandemic of the Bubonic plague
Arrived in 541 in Constantine the capital of the Roman Empire in the east
Raged Europe, North Africa and the Middle East until 757
1 million people died
Attempts at Control & Prevention
Quarantine isolation of the sick
Pest houses special hospitals where inflicted are isolated
Quick burials
Burning of clothes and bedding
Emphasis on studies of human anatomy
Changes to farming from growing of crops to raising of sheep for wool
Bigger ships with smaller crews
New diversified economy
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