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Intestinal Trematodes 191

Morphology and even progress to epileptic-like signs. Pulmonary
symptoms may include cough with chest pain, hemop-
This oval and brownish worm as an adult measures tysis (blood in sputum), and bronchitis. Eosinophilia is
roughly 10 mm in length and 8 mm in width. The eggs often present and the larval stage may migrate to the
of the oriental lung fluke are oval and measure, on aver- brain and produce neurological signs and symptoms.
age, 100 μm in length and 55 μm in width. The egg is
unembryonated when passed in the feces and the oper- Life Cycle
culated egg appears similar in size and shape to that of
the Diphyllobothrium latum tapeworm with the excep- The life cycle of the worm of the genus Paragonimus
tion that the lung fluke has opercular shoulders and a occurs widely in Asia and includes the countries of Japan,
thickened shell at the opposite end of the operculum as a Korea, Taiwan, China, the Philippines, and Thailand
differentiating characteristic. (Figure 8-5). Eggs from the adult larvae are coughed up in
the sputum from the lungs and swallowed. Upon reaching
Symptoms the intestines the eggs are passed in the stool and contam-
ination of fresh water sources ensues in some cases. Upon
The disease is manifested clinically in a number of hatching, miracidia are produced that invade certain
ways that range from the victims who appear perfectly species of snails. Large numbers of these stumpy-tailed
healthy to those with severe clinical signs and symptoms. cercariae leave the snail and crawl into the muscles and
Peritoneal infections often lead to dysentery, masses in visceral (gut) tissue of water creatures, such as crayfish
the abdominal region, and significant pain. Invasions of and crabs, which become the secondary or secondary
the central nervous system may lead to seizures, paralysis, intermediate hosts that inhabit fresh water. Humans eat

Source: Centers for Disease Control and Prevention (CDC)

FIGURE 8-5 Life cycle of Paragonimus westermani, one of the causal agents of paragonimiasis