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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

View in Context

eFigure 37–26. Life cycle of Paragonimus westermani (lung fluke). The eggs are excreted unembryonated in the sputum, or alternately, they are swallowed and passed with stool . In the external environment, the eggs become embryonated , and miracidia hatch and seek the first intermediate host, a snail, and penetrate its soft tissues . Miracidia go through several developmental stages inside the snail : sporocysts , rediae , with the latter giving rise to many cercariae , which emerge from the snail. The cercariae invade the second intermediate host, a crustacean such as a crab or crayfish, where they encyst and become metacercariae. This is the infective stage for the mammalian host . Human infection with P westermani occurs by eating inadequately cooked or pickled crab or crayfish that harbor metacercariae of the parasite . The metacercariae excyst in the duodenum , penetrate through the intestinal wall into the peritoneal cavity, then through the abdominal wall and diaphragm into the lungs, where they become encapsulated and develop into adults (7.5–12 mm by 4–6 mm). The worms can also reach other organs and tissues, such as the brain and striated muscles, respectively. However, when this takes place completion of the life cycle is not achieved because the eggs laid cannot exit these sites. Time from infection to oviposition is 65–90 days. Infections may persist for 20 years in humans. Animals such as pigs, dogs, and a variety of feline species can also harbor P westermani. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of P westermani.

Current Medical Diagnosis & Treatment 2024 > Paragonimiasis

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

View in Context

eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

View in Context

eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

View in Context

eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

View in Context

eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

View in Context

eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–28. Life cycle of Diphyllobothrium latum (broad fish tapeworm). Immature eggs are passed in feces . Under appropriate conditions, the eggs mature (approximately 18–20 days) and yield oncospheres, which develop into a coracidia . After ingestion by a suitable freshwater crustacean (the copepod first intermediate host) the coracidia develop into procercoid larvae . Following ingestion of the copepod by a suitable second intermediate host, typically minnows and other small freshwater fish, the procercoid larvae are released from the crustacean and migrate into the fish flesh where they develop into a plerocercoid larvae (sparganum) . The plerocercoid larvae are the infective stage for humans. Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection. Nevertheless, these small second intermediate hosts can be eaten by larger predator species, eg, trout, perch, walleyed pike . In this case, the sparganum can migrate to the musculature of the larger predator fish, and humans can acquire the disease by eating these later intermediate infected host fish raw or undercooked . After ingestion of the infected fish, the plerocercoid develop into immature adults and then into mature adult tapeworms, which will reside in the small intestine. The adults of D latum attach to the intestinal mucosa by means of the two bilateral groves (bothria) of their scolex . The adults can reach more than 10 M in length, with more than 3000 proglottids. Immature eggs are discharged from the proglottids (up to 1,000,000 eggs per day per worm) and are passed in the feces . Eggs appear in the feces 5–6 weeks after infection. In addition to humans, many other mammals can also serve as definitive hosts for D latum. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Diphyllobothrium latum.

Current Medical Diagnosis & Treatment 2024 > Noninvasive Cestode Infections

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–41. Life cycle of Dracunculus medinensis (Guinea worm). Humans become infected by drinking unfiltered water containing copepods (small crustaceans) that are infected with larvae of D medinensis . Following ingestion, the copepods die and release the larvae, which penetrate the host stomach and intestinal wall and enter the abdominal cavity and retroperitoneal space . After maturation into adults and copulation, the male worms die and the females (length: 70–120 cm) migrate in the subcutaneous tissues toward the skin surface . Approximately 1 year after infection, the female worm induces a blister on the skin, generally on the distal lower extremity, which ruptures. When this lesion comes into contact with water, a contact that the patient seeks to relieve the local discomfort, the female worm emerges and releases larvae . The larvae are ingested by a copepod and after 2 weeks (and two molts) have developed into infective larvae . Ingestion of the copepods closes the cycle. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the nematode or roundworm Dracunculus medinensis.

Current Medical Diagnosis & Treatment 2024 > Dracunculiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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eFigure 37–45. Life cycle of Gnathostoma spinigerum. In the natural definitive host (pigs, cats, dogs, wild animals), the adult worms reside in a tumor that they induce in the gastric wall. They deposit eggs that are unembryonated when passed in the feces . Eggs become embryonated in water, and eggs release first-stage larvae . If ingested by a small crustacean (Cyclops, first intermediate host), the first-stage larvae develop into second-stage larvae . Following ingestion of the Cyclops by a fish, frog, or snake (second intermediate host), the second-stage larvae migrate into the flesh and develop into third-stage larvae . When the second intermediate host is ingested by a definitive host, the third-stage larvae develop into adult parasites in the stomach wall . Alternatively, the second intermediate host may be ingested by the paratenic host (animals such as birds, snakes, and frogs) in which the third-stage larvae do not develop further but remain infective to the next predator . Humans become infected by eating undercooked fish or poultry containing third-stage larvae, or reportedly by drinking water containing infective second-stage larvae in Cyclops . (Adapted from a drawing provided by Dr. Sylvia Paz Díaz Camacho, Universidade Autónoma de Sinaloa, Mexico. Content source: Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of the Gnathostoma species.

Current Medical Diagnosis & Treatment 2024 > Gnathostomiasis

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