PARASITES IN HUMANS

Human parasites include various protozoa and worms which may infect humans, causing parasitic diseases. Human parasites are divided into endoparasites, which cause infection inside the body, and ectoparasites, which cause infection superficially within the skin. The cysts and eggs of endoparasites may be found in feces which aids in the detection of the parasite in the human host while also providing a means for the parasitic species to exit the current host and enter other hosts. Although there are number of ways in which humans can contract parasitic infections, observing basic hygiene and cleanliness tips can reduce its probability.

ARCHAELOGICAL EVIDENCE

It is assumed that early human ancestors generally had parasites, but until recently there was no evidence to support this claim. Generally, the discovery of parasites in ancient humans relies on the study of feces and other fossilized material. The earliest known parasite in a human was eggs of the lung fluke found in fossilized feces in northern Chile and is estimated to be from around 5900BC. There are also claims of hookworm eggs from around 5000BC in Brazil and large roundworm eggs from around 2330BC in Peru. Tapeworm eggs have also been found present in Egyptian mummies dating from around 2000BC, 1250BC, and 1000BC along with a well preserved and calcified female worm inside of a mummy .

WRITTEN EVIDENCE

The first written records of parasites date from 3000 to 400BC in Egyptian papyrus records. They identify parasites such as roundworms, Guinea worms, threadworms, and some tapeworms of unknown varieties. In ancient Greece, Hippocrates and Aristotle documented several parasites in his collection of works Corpus Hippocraticus. In this book, they documented the presence of worms and other parasites inside of fish, domesticated animals, and humans. The bladder worm is well documented in its presence in pigs along with the larval stages of a tapeworm (Taenia Solium). These tapeworms were mentioned in a play by Aristophanes as �hailstones� with Aristotle in the section about pig diseases in his book History of Animals. The cysts of the Echinococcus granulosus tapeworm were also well known in ancient cultures mainly because of their presence in slaughtered and sacrificed animals . The major parasitic disease which has been documented in early records is dracunculiasis. This disease is caused by the Guinea worm and is characterized by the female worm emerging from the leg. This symptom is so specific to the disease that it is mentioned in many texts and plays which predate 1000AD .

GREECE AND ROME

In Greece, Hippocrates and Aristotle created considerable medical documentation about parasites in the Corpus Hippocraticus. In this work, they documented the presence of parasitic worms in many animals ranging from fish to domesticated animals and humans. Among the most extensively documented was the Bladder Worm (Taenia solium). This condition was called �measly pork� when present in pigs and was characterized by the presence of the larval stages of the Bladder Worm in muscle tissue. This disease was also mentioned by the playwright Aristophanes when he referred to �hailstones� in one of his plays. This naming convention is also reflected by Aristotle when he refers to �bladders that are like hailstones.� Another worm which was commonly written about in ancient Greek texts was the tapeworm Echinococccus granulosus. This worm was distinguished by the presence of �massive cysts� in the liver of animals. This condition was documented so well mainly because of its presence in slaughtered and sacrificed animals. It was documented by several different cultures of the time other than the Greeks including the Arabs, Romans, and Babylonians . Not many parasitic diseases were identified in ancient Greek and Roman texts mainly because the symptoms for parasitic diseases are shared with many other illnesses such as the flu, the common cold, and dysentery. However, several diseases such as Dracunculiasis (Guinea worm disease), Hookworm, Elephantiasis, Schistosomiasis, Malaria, and Amebiasis cause unique and specific symptoms and are well documented because of this. The most documented by far was Guinea worm disease mainly because the grown female worm emerges from the skin which causes considerable irritation and which cannot really be ignored. This particular disease is widely accepted to also be the �fiery serpents� written about in the Old Testament of the Bible. This disease was mentioned by Hippocrates in Greece along with Pliny the Elder, Galen, Aetius of Amida, and Paulus Aegineta of Alexandria in Rome. Strangely, this disease was never present in Greece even though it was documented .

NORTHERN AFRICA,THE MIDDLE EAST AND MESOPOTAMIA

The medieval Persian doctor Avicenna records the presence of several parasites in animals and in his patients including Guinea worm, threadworms, tapeworms, and the Ascaris worm. This followed a tradition of Arab medical writings spanning over 1000 years in the area near the Red Sea. However, the Arabs never made the connection between parasites and the diseases they caused . As with Greek and Roman texts, the Guinea worm is very well documented in Middle Eastern medical texts. Several Assyrian documents in the library of King Ashurbanipal refer to an affliction which has been interpreted as Guinea Worm disease . In Egypt, the Ebers Papyrus contains one of the few references to hookworm disease in ancient texts. This disease does not have very specific symptoms and was vaguely mentioned. However vague the reference, it is one of the few that connects the disease to the hookworm parasite . Another documented disease is elephantiasis. Symptoms of this disease are highly visible, since it causes extreme swelling in the limbs, breasts, and genitals. A number of surviving statues indicate that Pharaoh Mentuhotep II is likely to have suffered from elephantiasis. This disease was well known to Arab physicians and Avicenna, who noted specific differences between elephantiasis and leprosy. That the disease schistosomiasis was extremely common in Ancient Egyptis suggested by mummified evidence, but it is not specifically documented in surviving texts. Other names for this disease include bilharzia, Katayama disease, Red Water fever, snail fever, and big belly. The only really defining symptom is bloody urine, but this can easily be overlooked as several other diseases exhibit the same symptom. However, the main reason it was not documented is probably because it was simply so common. In the same way, the Greeks and Romans did not acknowledge the existence of colds and coughs because of how common they were .

CHINA

The Chinese mostly documented diseases rather than the parasites associated with them. Chinese texts contain one of the few references to Hookworm disease found in ancient records, but no connection to hookworm is made . The Emperor Huang Ti recorded the earliest mentioning (2700BC) of malaria in his text Nei Ching. He lists chills, headaches, and fevers as the main symptoms and distinguished between the different kinds of fevers.

INDIA

In India, the Charaka Samhita and Sushruta Samhita document Malaria. These documents list the main symptoms as fever and enlarged spleens. The Brigu-Samhita from 1000BC makes the earliest reference to Amebiasis. The symptoms were given as bloody and mucosal diarrhea.

COMMONLY DOCUMENTED PARASITES

Protozoa

Plasmodium spp. - causes Malaria  Entamoeba - causes amoebiasis, amoebic dysentery Giardia  Toxoplasma gondii - causes Toxoplasmosis

Parasitic worms and flukes

Guinea worm (Dracunculus)  Schistosoma - causes Schistosomiasis  Strongyloides stercoralis - causes Strongyloidiasis  Guinea Worm - also known as Dracunculiasis 495. Hookworm  Tapeworm

Ectoparasites

Sarcoptes scabiei - causes scabies  Pediculus humanus capitis - causes headlice  Phthirus pubis - causes pubic lice  Ticks (Ixodoidea)

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