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Week #2 - Sherman Ch. 3, 4; Kiple P. 612-615.docx

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University of Toronto Scarborough
Health Studies
Caroline Barakat

(Reading) Week #2 | Sherman Ch. 3, 4; Kiple p. 612-615 Chapter 3 Six Plagues of Antiquity - diseases of antiquity (5000 BC to AD 7000) were characterized by parasites with long-lived transmission stages as well as those involving person-to-person contact; thus, most diseases became established only when a small number of infectious individuals could be maintained (when the disease became epidemic), which required population greater than a few hundred thousand The Pharaohs Plague (Nile Valley of Egypt) (snail fever/blood fluke disease) (endemic hematuria/schistosomiasis) A look back - causes blood to appear in the urine (hematuria) - widespread - chronic snail fever or blood fluke disease - water was infested with infected snails, resulting in a high level of disease - food production spread to other parts of Eurasia and North Africa; plants and domesticated animals also cultivated in the Nile Valley of Egypt, which triggered the rise of Egyptian civilization; however, also sowed the seeds of Egypts decline - deserts that bordered the Nile discouraged invasion, so people lived in relative security - all power was invested in the pharaohs, who were both kings and gods - below the pharaoh was a vast bureaucracy that included workers and peasantry - early civilizations of Egypt of those of the Fertile Crescent were based on agriculture, which required irrigation and/or natural flooding of rivers; irrigation farming created conditions favorable for the transmission of snail fever caused by blood fluke - blood fluke disease: corrosive disease - rule of pharaohs may have been due to the power of the snail and blood fluke and malaria, which debilitated the populace - by 660 BC, Egypt became subject to internal political discussion and attack by the Assyrians, and their civilization, based on agriculture and copper weapons, collapsed; Persians overran in 525 BC - cause of snail fever was unknown because of the transmission stages of the parasite (eggs, miracidia, and cercariae) are microscopic; as well, the adult worms themselves are tiny and live within small blood vessels, so they were unnoticed for thousands of years Search for the destroyer - blood fluke disease involved feces or urine, water, snails, and flatworm - soldiers of Napoleons army first to experience the disease during invasion of Egypt - bloody urine high frequency in men - connection between hematuria and a parasite was not made until Theodor Bilharz made a discovery that worms were found in the blood vessels, a location never encountered; worms called Distomum (two mouths); in 1858, name changed to Schistosoma; today, called schistosomiasis or bilharzias - Bilharz reported seeing microscopic eggs in a pointed spine in the female worm; in the following year, he observed these eggs in the bladder, and within the egg he observed a small, motile embryo; also found that the eggs would hatch to release a small, ciliated larva that swam around for about an hour and disintegrated - John Harley, examining the blood-tinged urine in a drop of water under the microscope, found schistosome eggs, several of which hatched to give progeny that swam by using their cilia - suspicion remained that humans acquired the infection either by eating infected snails or by drinking water containing the ciliated larvae, called miracidia - Spencer Cobbold found that the eggs hatched in fresh or brackish water - Japanese physicians found that a related blood fluke, named Schistosoma japonicum, could also infect humans, but this species had eggs without a spine - Patrick Manson discovered another type of schistosome egg, one with a spine on its side; named Schistosoma mansoni - miracidia able to penetrate freshwater snails in the rice paddies, and a tailed larva (cercaria) emerged from infected snails and could directly penetrate the skin of mice - snails Bulinus and Biomphalaria as vectors - infection acquired by bathing in infested water - cercariae that hatched from Biomphalaria produced eggs with lateral spines, where those from Bulinus produced eggs with a terminal spine - S. mansoni remained in the liver and laid its eggs there, whereas S. haematobium early in its development left the liver for the veins surrounding the bladder - life cycle of snail fever: on reaching fresh water, the discharged eggs releasing a swimming larva, miracidium, which are short-lived, but if they encounter a suitable snail, they penetrate the soft tissues (usually foot), migrate to liver, and change in form (sporocyst); for 6 to 7 weeks, by asexual reproduction, numbers of parasites increase; 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 Snail fever, the disease - sexes of schistosomes are separate and inhabit the blood vessels - adults live in blood vessels close to bladder and small intestine - pathology of schistosomiasis is due not to the adult worms but to the eggs - passage of eggs through the bladder wall that results in bleeding and gives the sign of hematuria - more than two-thirds of eggs fail to work their way out of the body and are washed back in the veins; by bloodstream, they accumulate in the liver and spleen; the piling of eggs blocks the normal blood flow, and this leads to tissue death - earliest infection occur within 1 to 2 months and are fever, chills, sweating, headache, and cough - six months to a year later, the accumulation of eggs produces organ enlargement in the liver and spleen, which causes the abdomen to become bloated, appetite diminishes, blood loss leads to anemia, and there is dysentery - schistosomiasis is arithmetic disease: severity of symptoms and damage related to number of worms present, and latter depends on the degree of exposure - over the centuries the adult inhabitants of areas of endemic disease, such as Africa, developed some immunity, as a result of continuous exposure; Europeans and Americans, with no immunity, suffer more severe symptoms as a result of higher worm burdens Where snail fever is found - wars and human migrations carried blood flukes of East Africa lakes to Nile River, and from there they were distributed along the trade routes to most continents of the world - estimated 200 million people infected, more than a million deaths annually - S. japonium found in Southeast Asia and western Pacific as well as China, Philippines, Indonesia - S. haematobium and S. mansoni found in 43 countries in Africa, but S. mansoni also found in Americas (Brazil, Suriname, Venezuela, Caribbean)- estimated 50 million cases in Africa; highest in children - the Aswan High Dam of Egypt, by controlling the level of water in Lake Nasser, has brought electricity to many parts of Egypt as well as making it possible to cultivate four crops per year through year-round irrigation; but also created favorable conditions for the schistosome-carrying snails - schistosomiasis first occurred in animals living in rainforests and lakes of East Africa and spread, with vector snails, along the Nile and out into Middle East and Asia via trade routes - blood flukes also in birds and mammals Snail fever today - preventive measures include education of the population in means to prevent transmission, treatment of infected persons, and control of snail vector using molluscicides - human exposure can be reduced by safe water supply for bathing and washing as well as sanitary disposal of human wastes - other measures may be lining irrigation channels with cement to discourage snails, intermittently irrigating rice paddies to disrupt the life cycle, or storing water away from snails for 2 to 3 days - earliest treatment required intravenous administration; 1929, intramuscular injections of another antimony compound (tartar emetic), stibophen used, but cure rates were not as good as those with tartar emetic; both drugs showed severe toxic reactions and sometimes death - later, an oral drug with low toxicity was developed: praziquantel - no preventive vaccine or drug for this disease - failure to control schistosomiasis due to the cost of molluscicides and drugs, as well as infrastructure for providing clean water and sanitary disposal of wastesbut it is the habits of human population that are critical importance to elimination of this disease The Plague of Athens (Ethiopia > Egypt > Athens) - land and climate of Greece were unsuitable for farming grains; as a result, the economy rested on the large-scale movements of goods by ship - planted vines and olive trees and produced wine and oil - democratic society: states consisting of a city and its surrounding lands whose inhabitants, citizens, were valued (slaves and women did not have same rights) - city-states consisted of urban centers dedicated to commercial transactions - inhabitants were healthy but not immune to diseases that were endemic in Middle East - at close of Dark Ages, there emerged two powerful city-states that were essentially military garrisons governed by commander and his captains: Athens (in Attica) and Sparta (on the Peloponnesus); each city-state represented opposing philosophies: stern military discipline in Sparta versus intellectual and political freedom in Athens - Peloponnesian war began
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