INTESTINAL PARASITES OF IMPORTANCE
There are many parasites that can infest the gastrointestinal tract of a soldier.
This lesson will discuss some of those parasites.
a. Entamoeba histolytica (pronounced EN-tuh-MEE-buh his-toe-LIT-i-kuh).
Entamoeba histolytica is a protozoan, a one-celled organism. Using microscopic
examination, one stage of the organism looks very similar to the amoeba you have
probably observed in some biology classes. Entamoeba histolytica is present
throughout the world, but it is found frequently in warm locations that have poor sanitary
conditions. The moving, feeding, and reproducing stage of the organism (the
trophozoite) lives in the lower gastrointestinal tract of the host. The organism can form
a cyst. A cyst is a stage of life that does not move and feed. This is the form of the
organism that infects the host. Humans ingest these cysts, which pass through the
gastrointestinal tract until they reach the lower intestine. There, the cysts become
trophozoites. Additional cysts are then formed and passed from the body in feces. The
cysts are spread by ingestion of feces-contaminated material or food. Poor sanitary
procedures contribute to the spread of the cysts. Fingers, fluid, flies, and other animal
carriers can all carry the cyst-contaminated material. Diseases caused by Entamoeba
histolytica include amebiasis, amebic dysentery, and amebic hepatitis (if the liver is
infected). Symptoms associated with these conditions include abdominal discomfort,
bloody dysentery, diarrhea, and fever.
b. Trichuris trichiura (pronounced trick-YOO-ris Trick-ee-YOO-ruh). Trichuris
trichiura has the common name of whipworm (see figure 2-1). The whipworm is a
parasitic roundworm that lives in the intestines. Humans are the main hosts of this
organism. Trichuris trichiura is commonly called a whipworm because it has a whip-like
head. The worm can reach a length of 50 mm. Infection is by ingestion of the eggs.
The host does not need to ingest any intermediate host. Once ingested, the larva
comes out of the eggshell in the upper part of the small intestine, and it remains in the
intestines. Eventually it imbeds a part of itself into the intestinal mucosa of the host,
where it obtains its nourishment. People who have had a heavy infestation of
whipworms usually have the following signs and symptoms: frequent and
blood-streaked loose stools, pain and tenderness in the abdomen, severe anemia, and
weight loss. Laboratory examination of the patient's stools can lead to a specific
identification of whipworm infestation. Infestations may be prevented by the sanitary
disposal of human wastes (feces), careful preparation of vegetables, washing of hands
before meals, application of principles of personal hygiene, and treatment of persons
infested with whipworms.