Ascariasis
The most common human roundworm infection, contracted via contaminated soil, causing GI upset, lung inflammation, and potentially intestinal or biliary blockage in heavy infections.
Emergency Management: Acute intestinal obstruction with suspected bowel ischemia/necrosis requiring emergent surgical resection.
Ascariasis is a parasitic infection caused by the large intestinal nematode (roundworm) Ascaris lumbricoides. It is the most common human helminthic infection globally. While mostly asymptomatic in mild cases, heavy worm burdens can cause severe intestinal obstruction, biliary colic, and malnutrition, particularly in children.
Detailed Overview
The lifecycle of Ascaris is complex. Humans ingest infective eggs from soil-contaminated food or water. The eggs hatch in the small intestine, and the larvae penetrate the gut wall, migrating through the venous system to the liver and then the lungs. In the lungs, they break into the alveoli, are coughed up, and swallowed back into the GI tract, where they mature into adult worms (which can grow 15-35 cm long). Adult worms live in the jejunum and consume the host's digested food. Severe complications arise mechanically when large tangles of adult worms obstruct the bowel or migrate into the biliary tree.
Epidemiology & Demographics
Infects an estimated 800 million to 1.2 billion people worldwide, predominantly in tropical and subtropical regions with poor sanitation and hygiene. Highest prevalence is in children aged 2 to 10 years.
Etiological Mechanism
Ascaris lumbricoides, a soil-transmitted helminth (STH).
Primary Causes
Ingestion of food, water, or soil contaminated with embryonated Ascaris eggs. Use of human feces as fertilizer ('night soil') heavily contributes to transmission.
Pathology occurs in two phases. 1) Pulmonary migratory phase: 4-16 days post-ingestion, larvae migrating through the pulmonary capillaries into alveoli cause local hemorrhage, eosinophilic inflammation, and exudate production (Loeffler's syndrome). 2) Intestinal phase: 6-8 weeks post-ingestion, adult worms in the jejunum cause mucosal inflammation. They secrete anti-trypsins to avoid digestion, which impairs host protein digestion, leading to malnutrition. A large bolus of worms can physically occlude the intestinal lumen. Worms also have a propensity to migrate into small orifices (Ampulla of Vater, appendix) when irritated by fever or certain drugs, causing acute biliary obstruction or appendicitis.
Diagnostic Criteria & Guidelines
Microscopic identification of Ascaris eggs in feces or macroscopic identification of passed adult worms. Ultrasound diagnosis is common for biliary complications.
Albendazole 400 mg orally as a single dose (acts by inhibiting microtubule polymerization in the parasite). Alternative: Mebendazole 100 mg BID for 3 days or 500 mg single dose. For biliary ascariasis without cholangitis, initial management is conservative (IV fluids, antispasmodics) as worms often spontaneously exit the duct back into the intestine, followed by anthelmintic therapy.
Second-Line & Adjunctive Therapy
Ivermectin 150-200 mcg/kg as a single dose. Pyrantel pamoate 11 mg/kg (max 1g) single dose is preferred for pregnant women, as Albendazole/Mebendazole are generally avoided in the first trimester due to teratogenic potential.
Surgical & Procedural Management
Endoscopic Retrograde Cholangiopancreatography (ERCP) to physically extract worms from the biliary tree if conservative management fails or if acute cholangitis/pancreatitis is present. Exploratory laparotomy and enterotomy to manually extract worms in cases of complete bowel obstruction, ischemia, or perforation.
Patient Counseling & Advice
Explain that treatment will cause the passing of dead worms in the stool over the next few days. Emphasize that re-infection is very common if environmental exposures (poor handwashing, contaminated soil) continue.
Follow-Up & Monitoring Schedule
Repeat stool O&P 2-3 weeks after treatment to confirm eradication (absence of eggs). If eggs persist, retreat.
Preventive Strategies
Mass drug administration (MDA) programs in endemic areas for schoolchildren (usually single-dose Albendazole twice yearly). Improvement of sanitation infrastructure and stopping the use of human feces as fertilizer.
Excellent with anthelmintic treatment for uncomplicated cases. Mortality is low but can occur with delayed surgical management of intestinal obstruction or ascending cholangitis.