Foodborne Animal Parasites 691
Order Pseudophyllidea
Family Diphyllobothriidae
Genus Diphyllobothrium
Order Cyclophyllidea
Family Taeniidae
Genus Taenia
Fascioliasis
This syndrome (also known as parasitic biliary cirrhosis and liver rot) is caused by the digenetic
trematode Fasciola hepatica. The disease among humans is cosmopolitan in distribution, and the
organism exists where sheep and cattle are raised; they, along with humans, are its principal definitive
hosts.
This parasite matures in the bile ducts, and the large operculate eggs (150 × 90 µm in size) enter
the alimentary tract from bile ducts and eventually exit the host in feces. After a period of 4–15 days
in water, the miricidium develops, enters a snail, and is transformed into a sporocyst. The sporocyst
produces mother rediae, which later become daughter rediae and cercariae. When the cercariae escape
from the snail, they become free swimming, attach to grasses and watercress, and encyst to form
metacercariae. When ingested by a definitive host, the metacercariae excyst in the duodenum, pass
through the intestinal wall, and enter the coelomic cavity. From the body cavity, they enter the liver,
feed on its cells, and establish themselves in bile ducts, where they mature.
19,79
Fascioliasis in cattle and sheep is a serious economic problem that results in the condemnation
of livers. Human cases are known, especially in France, and they are contracted from raw or improperly cooked watercress that contains attached metacercariae. Human cases are rare in the United
States and are limited to the South.
48 Pharyngeal fascioliasis (halzoun) in humans results from eating
raw Fasciola-laded bovine liver where young flukes become attached to the buccal or pharyngeal
membranes, resulting in pain, hoarseness, and coughing.
19
Symptoms, Diagnosis, and Treatment
Symptoms develop in humans about 30 days after the infection; they consist of fever, general malaise,
fatigue, loss of appetite and weight, and pain in the liver region of the body. The disease is accompanied
typically by eosinophilia. Fascioliasis can be diagnosed by demonstrating eggs in stools or biliary or
duodenal fluids. Effective treatment is achieved upon the administration of praziquantel.
79
Fasciolopsiasis
Fasciolopsiasis is caused by Fasciolopsis buski, and the habitat of this organism is similar to that of
F. hepatica. Humans serve as definitive host, several species of snails as first intermediate hosts, and
water plants (watercress nuts) as second intermediate hosts. Unlike F. hepatica, this parasite occurs in
the duodenum and jejunum of humans and pigs, and human infection rates as high as 40% are found
in parts of Thailand, where certain uncooked aquatic plants are eaten.
19
Human symptoms of fasciolopsiasis are related to the number of parasites, with no symptoms
occurring when only a few parasites exist in the body. When symptoms occur, they develop within
1–2 months after the initial infection and consist of violent diarrhea, abdominal pain, loss of weight,
Order Pseudophyllidea
Family Diphyllobothriidae
Genus Diphyllobothrium
Order Cyclophyllidea
Family Taeniidae
Genus Taenia
Fascioliasis
This syndrome (also known as parasitic biliary cirrhosis and liver rot) is caused by the digenetic
trematode Fasciola hepatica. The disease among humans is cosmopolitan in distribution, and the
organism exists where sheep and cattle are raised; they, along with humans, are its principal definitive
hosts.
This parasite matures in the bile ducts, and the large operculate eggs (150 × 90 µm in size) enter
the alimentary tract from bile ducts and eventually exit the host in feces. After a period of 4–15 days
in water, the miricidium develops, enters a snail, and is transformed into a sporocyst. The sporocyst
produces mother rediae, which later become daughter rediae and cercariae. When the cercariae escape
from the snail, they become free swimming, attach to grasses and watercress, and encyst to form
metacercariae. When ingested by a definitive host, the metacercariae excyst in the duodenum, pass
through the intestinal wall, and enter the coelomic cavity. From the body cavity, they enter the liver,
feed on its cells, and establish themselves in bile ducts, where they mature.
19,79
Fascioliasis in cattle and sheep is a serious economic problem that results in the condemnation
of livers. Human cases are known, especially in France, and they are contracted from raw or improperly cooked watercress that contains attached metacercariae. Human cases are rare in the United
States and are limited to the South.
48 Pharyngeal fascioliasis (halzoun) in humans results from eating
raw Fasciola-laded bovine liver where young flukes become attached to the buccal or pharyngeal
membranes, resulting in pain, hoarseness, and coughing.
19
Symptoms, Diagnosis, and Treatment
Symptoms develop in humans about 30 days after the infection; they consist of fever, general malaise,
fatigue, loss of appetite and weight, and pain in the liver region of the body. The disease is accompanied
typically by eosinophilia. Fascioliasis can be diagnosed by demonstrating eggs in stools or biliary or
duodenal fluids. Effective treatment is achieved upon the administration of praziquantel.
79
Fasciolopsiasis
Fasciolopsiasis is caused by Fasciolopsis buski, and the habitat of this organism is similar to that of
F. hepatica. Humans serve as definitive host, several species of snails as first intermediate hosts, and
water plants (watercress nuts) as second intermediate hosts. Unlike F. hepatica, this parasite occurs in
the duodenum and jejunum of humans and pigs, and human infection rates as high as 40% are found
in parts of Thailand, where certain uncooked aquatic plants are eaten.
19
Human symptoms of fasciolopsiasis are related to the number of parasites, with no symptoms
occurring when only a few parasites exist in the body. When symptoms occur, they develop within
1–2 months after the initial infection and consist of violent diarrhea, abdominal pain, loss of weight,