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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–43. Life cycle of Trichinella spiralis (trichina worm). Depending on the classification used, there are several species of Trichinella: T spiralis, T pseudospiralis, T nativa, T murelli, T nelsoni, T britovi, T papuae, and T zimbabwensis, all but the last of which have been implicated in human disease. Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. A second host is required to perpetuate the life cycle of Trichinella. The domestic cycle most often involves pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. In the sylvatic cycle, the range of infected animals is great, but animals most often associated as sources of human infection are bear, moose, and wild boar. Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae (except for T pseudospiralis and T papuae, which do not encyst) of Trichinella species . After exposure to gastric acid and pepsin, the larvae are released from the cysts and invade the small bowel mucosa where they develop into adult worms . Females are 2.2 mm in length; males 1.2 mm. The life span in the small bowel is about 4 weeks. After 1 week, the females release larvae that migrate to striated muscles where they encyst . Diagnosis is usually made based on clinical symptoms and is confirmed by serology or identification of encysted or nonencysted larvae in biopsy or autopsy specimens. (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Trichinella spiralis, or trichina worm.

Current Medical Diagnosis & Treatment 2023 > Trichinosis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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eFigure 35–45. 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 2023 > Gnathostomiasis

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