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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–14. Life cycle of Toxoplasma gondii. The only known definitive hosts for T gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces . Although oocysts are usually only shed for 1–2 weeks, large numbers may be shed. Oocysts take 1–5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water, or plant material contaminated with oocysts . Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites . Cats become infected after consuming intermediate hosts harboring tissue cysts . Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment . Humans can become infected by any of several routes: eating undercooked meat of animals harboring tissue cysts . consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat) . blood transfusion or organ transplantation . transplacentally from mother to fetus . In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens . Diagnosis of congenital infections can be achieved by detecting T gondii DNA in amniotic fluid using molecular methods such as PCR . (From Global Health, Division of Parasitic Diseases and Malaria, CDC.) A flowchart of the life cycle of Toxoplasma gondii.

Current Medical Diagnosis & Treatment 2024 > Toxoplasmosis

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eFigure 37–43. 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 2024 > Trichinosis

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eFigure 37–43. 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 2024 > Trichinosis

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eFigure 37–43. 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 2024 > Trichinosis

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eFigure 37–43. 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 2024 > Trichinosis

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eFigure 37–43. 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 2024 > Trichinosis

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eFigure 37–43. 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 2024 > Trichinosis

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