692 Modern Food Microbiology
and generalized weakness. Death may occur in extreme cases.
79 Symptoms appear to be due to the
general toxic effect of metabolic products of the flukes.
Diagnosis is made by demonstrating eggs in stools. The eggs of F. buski are 130–140 µm × 80–85
µm in size. Both niclosamide and praziquantel are effective in treating this disease.
79
Paragonimiasis
This parasitic disease (also known as parasitic hemoptysis) is caused by Paragonimus spp., especially
P. westermani. It is found primarily in Asia but also in Africa and South and Central America.
P. kellicotti is found in North and Central America. In contrast to the trematodes, P. westermani is a
lung fluke.
The eggs of this parasite are expelled in sputum from definitive hosts (humans and other animals),
and the miricida develop in 3 weeks in moist environments. A miricidium penetrates a snail (first
intermediate host) and later gives rise to daughter rediae and cercariae about 78 days after entering the
snail.
19 The cercariae enter a second intermediate host (crab or crayfish) and encyst. The crustacean
host in parts of the Orient and the Philippines are various species of freshwater crabs, where they
usually form metacercarial cysts in leg and tail muscle.
79 In P. kellicotti, cysts form in the heart
region.
79 When the definitive host ingests the infected crustacean, the metacercariae hatch out of their
shells, bore their way as young flukes through the walls of the duodenum, and then move to the
lungs, where they become enclosed in connective tissue cysts.
79 The golden-brown eggs may appear
in sputum 2–3 months later.
Symptoms, Diagnosis, and Treatment
Paragonimiasis is accompanied by severe chronic coughing and sharp chest pains. Sputum is often
reddish-brown or bloody. Other non-specific symptoms may occur when parasites lose their way to
the lungs.
79 Diagnosis is made by demonstrating the golden-brown eggs in sputum or stools. The
eggs of P. westermani are 80–120 µm in length and 50–60 µm in width. Also, a complement fixation
test titer of at least 1:16 is diagnostic, and ELISA tests are available. The disease can be treated with
praziquantel.
79
Clonorchiasis
The Class Trematoda of the flatworms consists of parasites commonly referred to as flukes that
infect the liver, lungs, or blood of mammals. Clonorchis (Opisthorchis) sinensis is the Chinese liver
fluke that causes oriental biliary cirrhosis. Flukes typically have three hosts: two intermediate, where
the larval or juvenile stage develops, and the definitive or final host, where the sexually mature adult
develops. C. sinensis is an endoparasite whose anterior sucker surrounds the mouth. It also has a
midventral sucker. Along with cats, dogs, pigs, and other vertebrates, humans may serve as definitive
hosts.
When deposited in water, the eggs of C. sinensis hatch into ciliated larvae (miracidia), which invade
the first host, usually a snail. As a larva enters the snail, it rounds up as a sporocyst and reproduces
asexually to form embryos. Each embryo develops into a redia that escapes from the sporocyst and
begins to feed on host tissues. Embryos within the rediae develop into cercariae, which escape from
and generalized weakness. Death may occur in extreme cases.
79 Symptoms appear to be due to the
general toxic effect of metabolic products of the flukes.
Diagnosis is made by demonstrating eggs in stools. The eggs of F. buski are 130–140 µm × 80–85
µm in size. Both niclosamide and praziquantel are effective in treating this disease.
79
Paragonimiasis
This parasitic disease (also known as parasitic hemoptysis) is caused by Paragonimus spp., especially
P. westermani. It is found primarily in Asia but also in Africa and South and Central America.
P. kellicotti is found in North and Central America. In contrast to the trematodes, P. westermani is a
lung fluke.
The eggs of this parasite are expelled in sputum from definitive hosts (humans and other animals),
and the miricida develop in 3 weeks in moist environments. A miricidium penetrates a snail (first
intermediate host) and later gives rise to daughter rediae and cercariae about 78 days after entering the
snail.
19 The cercariae enter a second intermediate host (crab or crayfish) and encyst. The crustacean
host in parts of the Orient and the Philippines are various species of freshwater crabs, where they
usually form metacercarial cysts in leg and tail muscle.
79 In P. kellicotti, cysts form in the heart
region.
79 When the definitive host ingests the infected crustacean, the metacercariae hatch out of their
shells, bore their way as young flukes through the walls of the duodenum, and then move to the
lungs, where they become enclosed in connective tissue cysts.
79 The golden-brown eggs may appear
in sputum 2–3 months later.
Symptoms, Diagnosis, and Treatment
Paragonimiasis is accompanied by severe chronic coughing and sharp chest pains. Sputum is often
reddish-brown or bloody. Other non-specific symptoms may occur when parasites lose their way to
the lungs.
79 Diagnosis is made by demonstrating the golden-brown eggs in sputum or stools. The
eggs of P. westermani are 80–120 µm in length and 50–60 µm in width. Also, a complement fixation
test titer of at least 1:16 is diagnostic, and ELISA tests are available. The disease can be treated with
praziquantel.
79
Clonorchiasis
The Class Trematoda of the flatworms consists of parasites commonly referred to as flukes that
infect the liver, lungs, or blood of mammals. Clonorchis (Opisthorchis) sinensis is the Chinese liver
fluke that causes oriental biliary cirrhosis. Flukes typically have three hosts: two intermediate, where
the larval or juvenile stage develops, and the definitive or final host, where the sexually mature adult
develops. C. sinensis is an endoparasite whose anterior sucker surrounds the mouth. It also has a
midventral sucker. Along with cats, dogs, pigs, and other vertebrates, humans may serve as definitive
hosts.
When deposited in water, the eggs of C. sinensis hatch into ciliated larvae (miracidia), which invade
the first host, usually a snail. As a larva enters the snail, it rounds up as a sporocyst and reproduces
asexually to form embryos. Each embryo develops into a redia that escapes from the sporocyst and
begins to feed on host tissues. Embryos within the rediae develop into cercariae, which escape from