PLAGUES AND PEOPLE LEC 2 - CHAPTER 3 & 4 - Plagues of Antiquity Bubonic Plague (Black Death).docx

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Published on 2 Jun 2012
School
UTSC
Department
Health Studies
Course
HLTB21H3
PLAGUES AND PEOPLE
CHAPTER 3 SIX PLAGUES OF ANTIQUITY (5000 BC to 700 AD)
2 million years ago, human populations were not exposed to infection because of small-group hunter
gatherers
-only diseases with very high transmission rates that induced little to none immunity, & macro parasitic
diseases not involving vectors for transmission and STD’s were able to establish themselves in groups of
hunter-gatherers
malaria and yellow fever came more existent after human populations settled down
agriculture provided increased amounts of food for the people, but it also contributed to the
conditions that would result in a decline in human health
-urban life enhanced the transmission of certain diseases through the air and water, by direct contact,
and by vectors such as snails, mosquitoes, and flies.
The diseases of antiquity (5000 BC to AD 700) were characterized by parasites with long-lived
transmission stages (ex: eggs) as well as those involving person-to-person contact
THE PHAROAHS’ PLAGUE (snail fever/blood fluke/ endemic hematuria)
1900 BC: Hematuria a disease that causes blood to appear in the urine
-was described by the father of Arabian medicine, Avicenna
disease undergoes transmission stages
Tomb of Ptah-Hetep I and Mehou of the VIth Dynasty at Sakarrah
- figures of fisherman and bargemen with enlarged abdomens, representing the pathology of chronic
snail fever or blood fluke disease
-found the calcified eggs of the blood fluke in the kidneys of mummies
Fossil snails capable of transmitting blood fluke disease have been found in the well water of Jericho
-people of Jericho defeated by Joshua’s army b/c of disease and inability to repair the decaying walls
-Joshua destroyed Jericho to prevent disease and remained deserted for 500 years
Snail Fever existed in tropical and subtropical parts of the world, especially in Egypt
Blood Fluke disease not a fatal disease, (unlike malaria and yellow fever), but it is a corrosive disease
Early civilizations of Egypt were based on agriculture (required irrigation and/or flooding by rivers)
-caused conditions favourable for the transmission of snail fever caused by the blood fluke
- Cause of snail fever : set Egyptian civilization on its inexorable downward spiral, was unknown to
ancient Egyptians because the transmission stages of the parasite (eggs, miracidia, and cercariae) are
microscopic. (adult worms are tiny and live within the small blood vessels, so they were unnoticed)
Blood Fluke also known as snail fever, endemic hematuria, involves feces or urine, water, snails,
and a flatworm
symptom: bloody urine (worms were found in blood vessels by Theodor Bilharz, a German physician
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working in Egypt
Theodor named the worm Distomum Haematobium but later changed to Schistosoma (split-body)
Today, Blood Fluke is called Schistomiasis or bilharzia
Bilharz reported seeing microscopic eggs with a pointed spine in the female worm
- he observed eggs found in the bladder and within egg, he observed a small, motile embryo.
-eggs would hatch to release small ciliated larva that swam for an hour and disintegrate
-infected by eating infected snails or by drinking water containing the ciliated larvae called miracidia
-eggs did not hatch in urine, but they did in fresh or brackish water
Schistosoma japonicum eggs without a spine (found in Southeast Asia and the Western Pacific)
Schistosoma mansoni eggs with spine on the side (found in Africa, Brazil, Venezuela, and the
Caribbean)
tailed larva called a cercaria emerged from infected snails and could directly penetrate the skin of
mice
-suggested that the infection was acquired by bathing in infested water
Leiper identified the snails Bulinius and Biomphalaria as the vectors
-he showed that when cercariae was placed in hydrochloric acid, they were killed
-also showed that the adult S. mansoni and S haematobium were different from each other and that
cercariae that hatched from Biomphalaria produced eggs with lateral spines
-cercariae hatched from Bulinus produced eggs with terminal spine
S. Mansoni remained in the liver and laid its eggs there
S. Haematobium early in development left the liver for the veins surrounding the bladder
Life cycle:
-reach fresh water
-discharge eggs releasing swimming larva called Miracidia
-Miracidia are short-lived, penetrate the soft-tissues, migrate to the liver, a change form (sporocyst)
-6-7 weeks, by asexual reproduction, parasites increase
-during that time, snail sheds thousands of fork-tailed cercariae, which can swim and directly penetrate
human skin
-5-8 weeks, develop into adult worms
Snail Fever, the disease
schistosomes: sexes are separate and they inhabit the blood vessels
-adult worms are ~10mm in length, stouter males have groove running lengthwise, called the
gynecophoric canal where female resides
-adults live in blood vessels close to the bladder and small intestine
-mating occurs in the gynecophoric canal, then paired worms move “upstream” into smaller veins where
female lays eggs
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-each day, 100s of embryo-containing eggs move across the walls of the veins into the bladder or
intestine, aided by the hosts inflammatory response, then eggs become enclosed in a small tumor called
a granuloma
it is the passage of eggs through the bladder wall that results in bleeding and gives the signal of
hematuria
-once in the bladder/intestine, egg becomes freed of granuloma and is eliminated from the body
through urine/feces
more than 2/3 of eggs are washed back in the veins by bloodstream and scattered throughout the
body
-accumulation is greatest in liver and spleen
-piling up of eggs block blood flow leading to tissue death
Earliest signs of infection occur within 1-2 months:
-fever, chills, sweating, headache, and cough
Six months- 1 year:
-accumulation of eggs increased, especially in liver and spleen. (enlarged liver causes the abdomen to
become bloated, appetite diminishes, blood loss
Origins
Schistosomiasis probably first occurred in animals living in the rainforests and lakes of East Africa and
then spread along the Nile and out into Middle East and Asia
Blood Flukes occur in birds and mammals other than humans
”swimmer’s itch” or “cercarial dermatitis” is found in lakes and along the seashore in Michigan,
Minnesota, Wisconsin, New Jersey, and New England that normally infect aquatic birds and mammals
-skin rash are the result of their failure to continue their migration past human skin
tartar emetic (treatment for schistosomiasis)
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Document Summary

Chapter 3 six plagues of antiquity (5000 bc to 700 ad) 2 million years ago, human populations were not exposed to infection because of small-group hunter gatherers. Only diseases with very high transmission rates that induced little to none immunity, & macro parasitic diseases not involving vectors for transmission and std"s were able to establish themselves in groups of hunter-gatherers. Malaria and yellow fever came more existent after human populations settled down. Agriculture provided increased amounts of food for the people, but it also contributed to the conditions that would result in a decline in human health. Urban life enhanced the transmission of certain diseases through the air and water, by direct contact, and by vectors such as snails, mosquitoes, and flies. The diseases of antiquity (5000 bc to ad 700) were characterized by parasites with long-lived transmission stages (ex: eggs) as well as those involving person-to-person contact. The pharoahs" plague (snail fever/blood fluke/ endemic hematuria)

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