Ascaris lumbricoides: Difference between revisions

Latest revision as of 14:04, 2 August 2020

Background

Life Cycle

Female worm releases egg into small intestine, which are passed in feces
They develop to become infectious eggs over 2 to 6 weeks, depending on environmental conditions
The eggs are then ingested, releasing the contained larva into the small intestine
Larvae penetrate the intestinal wall, enter the venous blood, and deposit into the lungs, where they climb the bronchial tree and are swallowed
- It matures in some way in the lungs
They reach the small intestine (again), where they develop into adults
Egg production starts about 2 months after initial ingestion
Adult worms live 10 to 24 months

Epidemiology

Likely the most common helminth infection worldwide, with a global distribution
Promoted by poor sanitation and by using human waste as fertilizer
Children often become infected when playing in contaminated soil
Ova can remain viable in soil for up to 6 years
It is unclear if it's still endemic in parts of the US, include Appalachia

Clinical Manifestations

Mostly asymptomatic
After 2 week incubation period, may develop pulmonary symptoms from a hypersensitivity response
- Non-productive cough, chest discomfort, low-grade fever, and eosinophilia
- Resolves by the time the worms mature
- Can rarely develop Löffler syndrome (eosinophilic pneumonia)
Once in the abdomen, the symptoms are usually mild
- May include mild abdo discomfort, dyspepsia, anorexia, or nausea
- If heavier worm burden, it can cause malnutrition
Can migrate, with adult worms exiting per rectum, mouth, tear duct, or nose (though all rare)

Complications

Malnutrition leading to intellectual stunting, poor school performance, and decreased growth
Can cause intestinal obstruction and intestinal performation when they amass
Can cause cholangitis, liver abscesses, pancreatitis, and appendicitis when they enter small orifices
- More common in adults

Diagnosis

Stool for ova, which should be easy to find due to the large amount of eggs released
Can also find larvae in sputum and gastric aspirates
PCR can detect them in stool
May appear as filling defects on bowel imaging

Management

Albendazole 400 mg po once, or mebendazole 500 mg po once, or mebendazole 100 mg po daily for 3 days, or pyrantel pamoate 11 mg/kg po once (max 1 g)
Ivermectin can also treat ascariasis 150 to 200 mcg/kg po once
In pregnancy and in children, albendazole and mebendazole can be used

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-== Microbiology ==
+==Background==
-== Life Cycle ==
+===Life Cycle===
+*Female worm releases egg into small intestine, which are passed in feces
-[[File:Ascariasis_LifeCycle_1.gif|Ascaris lumbricoides]]
+*They develop to become infectious eggs over 2 to 6 weeks, depending on environmental conditions
+*The eggs are then ingested, releasing the contained larva into the small intestine
+*Larvae penetrate the intestinal wall, enter the venous blood, and deposit into the lungs, where they climb the bronchial tree and are swallowed
+**It matures in some way in the lungs
+*They reach the small intestine (again), where they develop into adults
+*Egg production starts about 2 months after initial ingestion
+*Adult worms live 10 to 24 months
+===Epidemiology===
-* Female worm releases egg into small intestine, which are passed in feces
-* They develop to become infectious eggs over 2 to 6 weeks, depending on environmental conditions
-* The eggs are then ingested, releasing the contained larva into the small intestine
-* Larvae penetrate the intestinal wall, enter the venous blood, and deposit into the lungs, where they climb the bronchial tree and are swallowed
-** It matures in some way in the lungs
-* They reach the small intestine (again), where they develop into adults
-* Egg production starts about 2 months after initial ingestion
-* Adult worms live 10 to 24 months
+*Likely the most common helminth infection worldwide, with a global distribution
-== Epidemiology ==
+*Promoted by poor sanitation and by using human waste as fertilizer
+*Children often become infected when playing in contaminated soil
+*Ova can remain viable in soil for up to 6 years
+*It is unclear if it's still endemic in parts of the US, include Appalachia
+==Clinical Manifestations==
-* Likely the most common helminth infection worldwide, with a global distribution
-* Promoted by poor sanitation and by using human waste as fertilizer
-* Children often become infected when playing in contaminated soil
-* Ova can remain viable in soil for up to 6 years
-* It is unclear if it's still endemic in parts of the US, include Appalachia
+*Mostly asymptomatic
-== Clinical Presentation ==
+*After 2 week incubation period, may develop pulmonary symptoms from a hypersensitivity response
+**Non-productive cough, chest discomfort, low-grade fever, and eosinophilia
+**Resolves by the time the worms mature
+**Can rarely develop Löffler syndrome (eosinophilic pneumonia)
+*Once in the abdomen, the symptoms are usually mild
+**May include mild abdo discomfort, dyspepsia, anorexia, or nausea
+**If heavier worm burden, it can cause malnutrition
+*Can migrate, with adult worms exiting per rectum, mouth, tear duct, or nose (though all rare)
+===Complications===
-* Mostly asymptomatic
-* After 2 week incubation period, may develop pulmonary symptoms from a hypersensitivity response
-** Non-productive cough, chest discomfort, low-grade fever, and eosinophilia
-** Resolves by the time the worms mature
-** Can rarely develop Löffler syndrome (eosinophilic pneumonia)
-* Once in the abdomen, the symptoms are usually mild
-** May include mild abdo discomfort, dyspepsia, anorexia, or nausea
-** If heavier worm burden, it can cause malnutrition
-* Can migrate, with adult worms exiting per rectum, mouth, tear duct, or nose (though all rare)
+*Malnutrition leading to intellectual stunting, poor school performance, and decreased growth
-=== Complications ===
+*Can cause intestinal obstruction and intestinal performation when they amass
+*Can cause cholangitis, liver abscesses, pancreatitis, and appendicitis when they enter small orifices
+**More common in adults
+==Diagnosis==
-* Malnutrition leading to intellectual stunting, poor school performance, and decreased growth
-* Can cause intestinal obstruction and intestinal performation when they amass
-* Can cause cholangitis, liver abscesses, pancreatitis, and appendicitis when they enter small orifices
-** More common in adults
+*Stool for ova, which should be easy to find due to the large amount of eggs released
-== Diagnosis ==
+*Can also find larvae in sputum and gastric aspirates
+*PCR can detect them in stool
+*May appear as filling defects on bowel imaging
+==Management==
-* Stool for ova, which should be easy to find due to the large amount of eggs released
-* Can also find larvae in sputum and gastric aspirates
-* PCR can detect them in stool
-* May appear as filling defects on bowel imaging
+*[[Is treated by::Albendazole]] 400 mg po once, or [[Is treated by::mebendazole]] 500 mg po once, or [[Is treated by::mebendazole]] 100 mg po daily for 3 days, or [[Is treated by::pyrantel pamoate]] 11 mg/kg po once (max 1 g)
-== Management ==
+*[[Is treated by::Ivermectin]] can also treat ascariasis 150 to 200 mcg/kg po once
+*In pregnancy and in children, [[albendazole]] and [[mebendazole]] can be used
-* Albendazole 400 mg po once, or mebendazole 500 mg po once, or mebendazole 100 mg po daily for 3 days, or pyrantel pamoate 11 mg/kg po once (max 1 g)
-* Ivermectin can also treat ascariasis 150 to 200 mcg/kg po once
-* In pregnancy and in children, albendazole and mebendazole can be used
 {{DISPLAYTITLE:''Ascaris lumbricoides''}}