Chapter 3-Six plagues of antiquity.docx

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17 Mar 2012
Chapter 3-The Six plagues of Antiquity
As humans changed their lifestyles their relationship with infectious diseases came to be
For 2 million years these human populations consisted of small groups of hunter-gatherers
with limited contact with other such groups and there were no domesticated animals. Such
a population structure, with little or no exposure to new sources of infection and with
minimal survival and transmission parasites led to a situation where epidemic diseases were
virtually non existent
Only diseases with very high transmission rates that induced little or no immunity as well as
macro parasitic diseases that did not involve vectors for transmission and sexually
transmitted diseases were able to establish themselves in the groups of hunter-gatherers
It was only until human populations settled down and adopted an agricultural life, or
continued a nomadic existence that depended on the husbandry of large groups of animals
that conditions favoured the emergence of epidemic diseases (plagues)
Agriculture provided increased amounts of food for the people but it also contributed to
conditions that would result in a decline in human health
o The Agricultural Revolution with the cultivation of crops and animal husbandry that
provided the driving force for the growth of human cities (urbanization). Urban life
also 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 with
antiquity were characterised by long lived transmission stages as well as those
involving person to person contact.
The Pharaohs’ Plague
A look back
Assyrian and Babylonan literature as well as the Egyptian papyrus from the Kahun
describes a disease that causes blood to appear from the urine called hematuria
Such a sign was not considered to be connected with disease, but to be a mark of
puberty in the male child.
In a relief of the tomb of Ptah-Hetep I and Mehou of the VIth Dynasty at Sakkarah
there are figures with enlarged abdomens surely representing the pathology of snail
fever or blood fluke disease
In 1910 Marc Almand Ruffer examined several Egyptian mummies and found several
calcified eggs of the blood fluke in the kidneys of several mummies
Fossil snails capable of transmitting blood fluke disease have been found in the well
water of Jericho. It has been predicted that the water was infested with infected
snails, resulting in a high level of disease
The people of Jericho were so defeated by the disease that they were easily
defeated by Joshua’s army . The city remained deserted for 500 years and centuries
of recurring drought destroyed all the snails, and the city remained free from
disease to this day.
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Soon after food production began in the Fertile Crescent it spread to other parts of
Eurasia and North Africa. The plants and domesticated animals formed the basis for
agriculture in the valley s and triggered the rise of Egyptian civilization.
Egypt, despite its beautiful architecture was deeply affected by snail fever. The
disease could not be kept under control because:
o The early civilizations of Europe and those of the Fertile Crescent (Summer,
Assyria, and Babylon) were based on agriculture , which required irrigation
and/or natural flooding by the rivers.
o Irrigation farming especially in the tropics created conditions favourable for
the transmission of snail fever caused by the blood fluke
o Blood fluke disease is not a fatal disease but its corrosive
o The rule of the pharaohs may have been due to the power of the snail and
the blood fluke and malaria- the classic plagues of Egypt which debilitated
the population.
o Egypt was subjected to internal political dissension and attack by their iron-
armed neighbours (the Assyrians) and their civilization which was based on
agriculture and copper weapons began to collapse.
o The cause of snail fever was unknown to the Egyptians because the
transmission stages of the parasites (eggs, miracidia, and cercariae ) are
microscopic and the adult worms are tiny and live within small blood vessels
Blood fluke Disease
Blood fluke disease, also known as snail fever or endemic hematuria, involves feces or
urine, water, snails and a flatworm
The first people to experience this disease was the soldiers of Napoleon’s army during
the invasion of Egypt. The symptom of the disease , bloody urine, was rife among the
soldiers but many believed that it was the excessive heat that caused this condition
Billharz a German physician working in Egypt discovered worms in the blood vessels
Schistosoma , blood fluke disease is called schistosomiasis or bilhazaria due to Bilharz’s
In 1851 Bilharz reported seeing microscopic eggs with a pointed spine in a female worm,
he observed these eggs in the bladder and within the egg he observed a small motile
He found that the egg would hatch to release a small ciliated larva that swam around for
about an hour until in disintegrated.
Also by examining the blood tinged urine under a microscope he found schistosome
eggs several of which hatched to give progency that swam by using their cilia
The suspicion remained that humans acquired the infection either by eating infected
snails or by drinking water containing the ciliated larvae, called miracidia.
There were three known species of the human infecting blood flukes: Schistosoma
japonicium, schistosoma mansoni
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When tails of mice were immersed in water from the rice fields known to have high
incidence of bilharzia, they became infected with S. japonicium
Tailed larvae (cercaria) emerged from infected snails and could directly penetrate the
skin of mice
Snails bulinis and biomphalaria were the vectors of snail disease . Leiper proved that the
skino f mice could be directly invaded the the cercariae by placing the tails in cercariae
infested water (suggests that the infection was spread by bathing in infested water)
The life cycle of snail fever was finally discovered
o On reaching fresh water, the discharged eggs release a swimming larva, the
miracidium. Miriacidia are short lived but if they encounter a suitable snail they
penetrate the soft tissues (usually the foot) , migrate to the liver , and change in
form (sporocyst). For up to 6-7 weeks by asexual reproduction, the numbers of
parasites increase. During this time, the snail sheds thousands of fork tailed
cercarieae which can swim and directly penetrate the human skin and in 5-8
weeks they develop into adult worms.
Schistosomes differ from other flukes in that the sexes are separate and they inhabit the
blood vessels . The adult worms are 10 mm in length and the stouter males have a
groove running lengthwise, called the gynecophoric canal. Schistosoma split body.
Both males and females have two suckers at the head end of the worm, and the more
anterior one surrounds the mouth.
The schistosome adults, in copula, live in blood vessels (veins) close to the bladder and
small intestine. Mating occurs in the gynecophoric canal, and then the paired worms
move “upstream” into the smaller veins, where the female worm deposits the fertilized
eggs. Each day, hundreds of embryo-containing eggs move aross the walls of the veins
into the bladder and intestine, aided by the hosts’ inflammatory response, and in the
process 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 telltale sign of
hematuria. Once in the bladder or intestine, the egg becomes freed of the granuloma,
and is eliminated from the body in the urine or feces.
However, 2/3 of the eggs fail to work their way out of the body and are washed back in
the veins, by means of the bloodstream, they scatter throughout the body, where they
accumulate in various organs. Accumulation is the GREATEST in the liver and the spleen.
The piling up of eggs blocks normal blood flow, which can lead to tissue death.
The eggs act as an irritating foreign substance, that the body attempts to wall off by
surrounding it with a fibrous capsule. The egg-laden liver becomes filled with scar tissue
SIGNS OF INFECTION: fever, chills, sweating, headache, and cough. Six months to a year later,
the accumulation of eggs produces organ enlargement, especially the liver and spleen , and the
enlarged liver causes the abdomen to become bloated, appetite diminishes , blool loss leads to
Anemia and there is dysentery
Schistosomiasis is dependent on how severe the symptoms are and the cumulative
damage is based on the number of worms present
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