Plagues and People; Chapter 3

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14 Mar 2012

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Chapter 3 – Six Plagues of Antiquity:
- Plagues came to be a record only in our recent past, in a time when we became farmers (less
plagues in the hunter-gatherers time, no domestication)
-Vectors of Malaria and Yellow Fever may have been present at the hunter-gatherer stage
- The diseases of antiquity (500 BC t o700 AD) where characterized by parasites with
long-lived transmission stages (ex.eggs) and also person-to-person contact
- The were characterized by parasites with long-lived transmission stage; as well those that
involved person to person contact
- The Pharaoh’s Plague (blood fluke disease): The disease that causes blood to appear in the
urine (hematuria)
- In 1910 Marc Armand Ruffer examined Egyptian mummies and found the calcified eggs of
the blood fluke in the kidneys of several. Fossil snails capable of transmitting blood fluke
disease have been found in the well water of Jericho
- Snail fever has existed in tropical and sub tropical parts of the world especially Egypt
- Blood fluke and pharaohs plague disease are not as fatal as Malaria and yellow fever, but
they are corrosive
- Snail fever: also known as blood fluke or endemic Hematuria (blood in the urine),
involves feces or urine, water, snails and a flatworm
- The soldiers of Napoleon’s army during the invasion of Egypt (1799 to 1801) where the
first Europeans to Experience it
Bloody urine is a symptom of the disease and had a higher frequency in men
- Blood fluke disease is also called schistosomiasis or bilharzia
- Theodor Bilharz, a German physician working in Egypt made a discovery that worms where
found in the blood vessels. He named the worm Distomum Haematobium, which in 1858 was
then changed to Schistosoma
- In 1851 Bilharz saw microscopic eggs in the female worm with a pointed spine. A year later
her saw these eggs in the bladder and within the eggs he saw a small motile embryo. The eggs
would hatch to release a small, ciliated larva that swam around for an hour and then
- In 1870 Spencer Cobbold found that although the eggs don’t hatch in urine, they do in fresh
or brackish water
- In 1904 japanese physicians found that a related blood fluke named Schistosoma japonicum
could also infect humans but it had eggs without a spine (another know species of human
effecting blood flukes)
- In 1905 Patrick Manson discovered a schistosome egg with a spine on its side, which was in the
feces of an English man who had never visited Africa. It was named Schistosoma mansoni.
(Another known species of human effecting blood flukes)
- 3 forms of blood fluke that infect humans
- Infection was acquired by bathing in infested water
- The snails “Bulinus” and “Biomphalaria” where the vectors of blood fluke
- Cercariae that hatched from Biomphalaria produced eggs with lateral spines and those
from Bulinus produced eggs with a terminal spine
- S.mansoni remained in the liver and laid its eggs there, whereas S.haematobium left the
liver for the veins surrounding the bladder
- Life cycle of snail fever: on reaching the fresh water, the discharged eggs release a swimming
larva, the miracidium. Miracida are short-lived, but if they encounter suitable snail they penetrate
the soft tissues (usually the foot), migrate to the liver, and change in form (sporocyst); for 6 to 7
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weeks by asexual reproduction, the number of parasites increase. During this time, the snail sheds
thousands of fork-tailed Cercariae, which can swim and directly penetrate human skin, and in 5 to
8 weeks they develop into adult worms.
- Schistosomes differ from other flukes because the sexes are separate and they inhabit the blood
vessels. Both male and females have 2 suckers on the head. The males have a groove running
lengthwise called the gynecophoric canal, and this is where the female resides (split bodies)
- Usually live in the blood vessels and small intestine
- Mating also happens here and then the paired worms move up into smaller veins where the
female worm deposits the fertilized eggs.
- The eggs move across the walls of the veins to the bladder or intestine and become enclosed in a
small tumor called a granuloma.
- The bleeding and sign of hematuria occurs when the eggs pass through the bladder walls
- Once in the bladder or intestine, egg becomes freed of the granuloma and is eliminated for the
body as urine or feces
- More than 2/3 of the eggs do not make their way out of the body and are washed back to the
veins through the bloodstream an then scatter through the body and accumulate in various organs
(mostly in liver and spleen)
- Piling up of eggs blocks normal blood flow and leads to tissue death. Liver is eventually is filled
with scar tissue
- In bladder blood fluke S. Haematobium, scarred area blocks migration of eggs through the
lower bowel tissues, and more eggs are swept back into other sites.
- Earliest sign of infection occur first or 2nd month; are fever, chills, sweating, headache and
cough. 6 months to a year later the buildup of eggs causes organ enlargement, especially spleen
and liver. Liver enlargement then causes bloated abdomen, loss of appetite, loss of blood which
leads to anemia
- Schistosomiasis is an arithmetic disease: severity of symptoms and damage is directly related to
the number of worms present
- Wars an human migrations carried blood flukes of the East African Lakes to the Nile River, and
then they were distributed along the trade routes to most of the countries in the world
- Currently 200 million people have schistosomes, resulting in a million deaths annually.
- Remains one of Africa’s greatest tragedies with 50 million cases
- S.Japonicum- Southest Asia, Western Pacific, China, Philippines and Indonesia
- S. Haematobium and S. Mansoni- 43 countries in Africa
- S. Mansoni- Americas (Brazil, Venezuela, Suriname and Caribbean
- Mostly occurs to children
- First occurred in animals living in the rainforest and lakes of East Africa and then spread with
the vector snails along the Nile and out to the Middle East and Asia via the trade routes
- Blood fluke occurs in humans, birds and mammals
- Diagnostic today is by examining urine under the light microscope and stool and finding eggs.
-No preventive vaccine or drugs. Praziquantel(1970) a drug of treating blood fluke, non-
The Plagues of Athens: in 430 BC an epidemic that started in Ethiopia moved into Egypt and
was bought by ship to Piraeus. It raged for 2 years and killed 1/4th of the Athenians, including
Pericles in 429 BC.
- In 1994-1995 a mass grave was uncovered outside Athens’ ancient cemetery containing 90
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