INTRODUCTION TO PARASITOLOGY
Section I. OVERVIEW OF PARASITOLOGY
Today the third world countries are in constant fight for their survival against
parasites. However, parasitic infections are not restricted to any particular geographical
location and many researchers believe that the United States is heading toward an
epidemic due to parasites. The size of parasites is varied, from minute microscopic
forms to some measuring as much as 10 meters in length. Their life cycles can be as
uncomplicated as simple cell division or so complex as to need two intermediate hosts
to complete the required larval molting. Most parasites survive better in tropical
weather, but there are some that have a predilection for cold climates.
HISTORY OF PARASITOLOGY
The history of the world is full of cases where parasitic diseases are mentioned.
From the parasites found in the Egyptian mummies to various references used in the
Bible, man has known and battled parasites since the beginning of recorded history.
a. Ancient History. The Ebers papyrus, written about 1600 BC, contains
references to the presence of parasitic worms in man. The laws of the Mosaic code
prohibiting the consumption of meat from unclean animals indicate that the early
Israelites had knowledge about parasitic infections. There is also evidence of parasitic
recognition among the Roman, Greek, Persian, and Phoenician scientists. Chinese
doctors were aware of parasites as early as 300 BC.
b. Modern History. The liver fluke Fasciola hepatica was discovered by Jehan
de Brie in 1379 from sheep. Anton Van Leewenhoek (1632-1723) described the
morphology of the protozoan Giardia lamblia from his own stool. In 1880, Laveran
demonstrated the intracellular parasites of malaria. These are but a few of the many
discoveries made in the nineteenth and twentieth century that expanded the field of
c. Misconceptions. Parasites were thought to be beneficial to humans during
the seventeenth and eighteenth centuries. For example, many people believed that lice
protected children from disease and leeches were used extensively for blood letting as
a cure. For a time, intestinal parasites were thought to help in cleaning the tract of
excess food and waste and until recently, the Chinese believed that powdered Ascaris
was helpful for medicinal treatment of impotency. In France, the heads of tapeworms
(scolices) were once used as weight control measures.