Etiology and Treatment of Ascariasis
Etiology
Ascariasis is caused by the roundworm Ascaris lumbricoides, transmitted through the fecal-oral route via ingestion of embryonated eggs from fecal-contaminated food, water, or soil. 1
Transmission and Risk Factors
- Transmission occurs through ingestion of embryonated eggs from fecal-contaminated material in areas with poor sanitation and inadequate sewage disposal 1
- Highest prevalence occurs in tropical and subtropical regions, particularly in rural settings of Africa, Asia, and South America 2
- Key risk factors include poverty, poor sanitation, inadequate sewage disposal, poor personal hygiene, and use of human fecal matter as fertilizer 1
- Children younger than 5 years have the greatest prevalence 1
- Worldwide distribution affects more than 1.2 billion people, making it the most common helminthic infection globally 1, 3
Life Cycle and Pathophysiology
- After ingestion, larvae migrate through the pulmonary system for maturation before returning to the intestinal tract 3
- Adult worms reside in the small intestine where they can cause various complications depending on worm burden 3
Treatment
The first-line treatment for ascariasis is a single oral dose of albendazole 400 mg, mebendazole 500 mg, or ivermectin 200 μg/kg. 2
Medication Regimens
- Albendazole 400 mg as a single oral dose achieves cure rates exceeding 95% 2, 4
- Mebendazole 500 mg as a single oral dose is equally effective with similar cure rates 2, 4
- Ivermectin 200 μg/kg as a single oral dose is an alternative option 2
- All patients with confirmed A. lumbricoides infection warrant anthelminthic treatment, even if asymptomatic, to prevent complications from parasite migration 1
Special Populations
- Pregnant women should be treated with pyrantel pamoate rather than albendazole or mebendazole 1
- Children can safely receive albendazole or mebendazole 1
Clinical Presentations Requiring Treatment
Loeffler's Syndrome (Pulmonary Phase)
- Presents with fever, dry cough, wheezing, and urticarial rash during larval migration 2
- Treat with albendazole 400 mg or mebendazole 500 mg as a single dose 5
- Consider repeating treatment one month after resolution of pulmonary symptoms 5
- Exercise caution with corticosteroids if Strongyloides coinfection is possible 5
Intestinal Complications
- Gastrointestinal obstruction (particularly in children) and biliary obstruction (more common in adults) may occur 2
- Intestinal or biliary obstruction may require surgical intervention in addition to anthelmintic therapy 2
- Mechanical obstruction by a bolus of worms is the most common cause of bowel obstruction, occurring at a rate of 2 per 1000 infected people 6
- Volvulus with perforation is a rare but serious complication requiring emergency surgical management 7
Diagnosis
Concentrated stool microscopy is the first-line diagnostic test, with fecal PCR being a higher sensitivity alternative when available 2
Diagnostic Methods
- Direct visualization of adult worms passed in stool is diagnostic when present 2
- Microscopic examination of fecal smears or concentration techniques for characteristic ova establishes the diagnosis 1
- Ultrasonography can detect worms in the biliary tract and pancreas for hepatopancreatic ascariasis 3
- ERCP can diagnose biliary and pancreatic ascariasis and extract worms when indicated 3
Follow-up and Prevention
No specific follow-up is typically needed after successful treatment unless symptoms persist 2
Prevention Strategies
- Health education, personal hygiene, improved sanitary conditions, proper disposal of human excreta, and discontinuing use of human fecal matter as fertilizer are effective long-term preventive measures 1
- Mass drug administration should be repeated periodically in endemic areas, as most treated patients become re-infected within months 1
- Water, sanitation, and hygiene (WASH) programs are highly effective but access and follow-up remain challenging in refugee camps and resource-limited settings 8
Important Caveats
- Reinfection is common in endemic areas, with most treated patients becoming re-infected within months despite successful initial treatment 1
- Ascariasis may reappear in certain at-risk populations in industrialized countries, particularly among immigrants and refugees from endemic regions 8
- Detection, treatment, and follow-up remain challenging even in wealthy, industrialized countries with refugee populations 8