Heterophyiasis is infection with the intestinal fluke Heterophyes heterophyes, which is acquired by eating infected raw or undercooked fish from freshwater or brackish water.

F buski, known as the giant intestinal fluke, is found in the duodenum and jejunum of pigs and humans and is the largest intestinal fluke to parasitize humans. Humans are infected by eating freshwater aquatic plants such as water caltrops, water chestnuts, and water bamboo, which can harbor the metacercariae.

Heterophyiasis occurs in the Middle East, Far East, and Egypt. The clinical features of the disease include severe and fluctuating abdominal pain and diarrhea. When the eggs of the flukes move into the heart, fatal valvular and myocardial damage may occur.

Causal Agents. The trematode Heterophyes heterophyes, a minute intestinal fluke.

Metagonimiasis is an infectious parasitic disease that is associated with eating undercooked fish. It is found mostly in the Far East, but also in Siberia, Manchuria, the Balkan states, Israel and Spain.

Schistosoma. Unlike all other trematodes, schistosomes are not hermaphroditic but dioecious, forming separate sexes. Adult worms have elongate tubular bodies, each male having a unique gynecophoral canal (schisto-soma = split body) in which a female worm resides.

Schistosomiasis, also known as bilharzia, is a disease caused by parasitic worms. Although the worms that cause schistosomiasis are not found in the United States, people are infected worldwide. In terms of impact this disease is second only to malaria as the most devastating parasitic disease.

C. Clonorchis sinensis adults are flattened, lance shaped, and measure approximately 10 to 25 mm long by 3 to 5 mm wide. The oral and ventral suckers (acetabulum) are relatively small. Like other flukes, they are hermaphroditic.

Life Cycles of Intestinal Trematodes The infective stage (metacercaria) can be found in a wide variety of freshwater and brackish water fishes. Perhaps most important are Haplorchis spp., Heterophyes heterophyes, and Metagonimus yokogawai.

Clonorchis sinensis, the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on bile.

Adults of Paragonimus spp. are large, robust, ovoid flukes. They are hermaphroditic, with a lobed ovary located anterior to two branching testes. Like all members of the Trematoda, they possess oral and ventral suckers.

Adults of Heterophyes heterophyes are minute flukes, measuring 1-2 mm in length. The tests are large and paired, and are situated near a small ovary. The surface of the worm is covered with minute spines. Adults reside in the small intestine of the definitive host.

In this figure, the following structures are labeled: oral sucker (OS), pharynx (PH), intestine (IN), ventral sucker, or acetabulum (AC), and eggs within the uterus (UT) Snail intermediate hosts of Heterophyes heterophyes. Like all trematodes, Heterophyes heterophyes requires a snail as an intermediate host.

In addition to humans, various fish-eating mammals (e.g., cats and dogs) and birds can be infected by Heterophyes heterophyes . Egypt, the Middle East, and Far East. The main symptoms are diarrhea and colicky abdominal pain.

Adults reside in the small intestine of the definitive host. Figure A: Adult of H. heterophyes, stained with carmine. In this figure, the following structures are labeled: oral sucker (OS), pharynx (PH), intestine (IN), ventral sucker, or acetabulum (AC), and eggs within the uterus (UT)