Ascariasis (Roundworm)

An intestinal helminthic infection caused by the nematode Ascaris lumbricoides,

Aetiology

Causative organism:

Parasite	Characteristics
Ascaris lumbricoides	Large intestinal nematode

Key morphology:

Feature	Description
Adult worm	Cylindrical, tapered ends
Female worm	20–35 cm long
Male worm	15–30 cm long, curved tail
Eggs	Thick shell, mammillated surface

Pathophysiology

The infection occurs via the fecal–oral route.

Life Cycle Stages

Ingestion of embryonated eggs in contaminated food or water

Eggs hatch in the duodenum

Larvae penetrate intestinal mucosa

Larvae migrate via portal circulation → liver → lungs

In lungs, larvae enter alveoli and ascend the bronchial tree

Larvae are swallowed back to the intestine

Adult worms mature in the small intestine

Duration of life cycle: 2–3 months

Pulmonary Migration Phase

Larval migration through lungs causes:

Löffler syndrome

Features:

Transient pulmonary infiltrates

Peripheral eosinophilia

Cough and wheezing

Clinical Presentation

Pulmonary Phase (Larval Migration)

Symptom	Mechanism
Dry cough	Lung irritation
Wheezing	Airway inflammation
Dyspnea	Pulmonary infiltrates
Fever	Inflammatory response
Eosinophilia	Immune response

Intestinal Phase (Adult Worms)

Symptom	Cause
Abdominal pain	Intestinal irritation
Nausea and vomiting	Intestinal obstruction
Malnutrition	Nutrient competition
Growth retardation (children)	Chronic infection
Worms in stool or vomitus	Heavy infestation

Complications

Heavy worm loads may cause mechanical obstruction.

Complication	Mechanism
Intestinal obstruction	Worm bolus
Biliary obstruction	Migration into bile duct
Cholangitis	Bacterial infection
Pancreatitis	Worm entering pancreatic duct
Appendicitis	Worm obstruction
Hepatic abscess	Biliary invasion

Investigations

Stool Examination (Gold Standard)

Test	Finding
Stool microscopy	Ascaris eggs
Direct smear	Fertilized or unfertilized eggs

Egg morphology:

Type	Feature
Fertilized egg	Thick shell, mammillated surface
Unfertilized egg	Elongated and irregular

Blood Tests

Test	Result
CBC	Eosinophilia
IgE	Elevated
Inflammatory markers	Mild elevation

Classic ultrasound sign:

“Spaghetti sign” (biliary ascariasis)

Imaging

Investigation	Finding
Abdominal X-ray	Worm masses
Ultrasound	Linear echogenic worms in biliary tree
CT scan	Intestinal obstruction

Management

First-Line Anthelmintic Drugs

Drug	Dose
Albendazole	400 mg SD
Mebendazole	100 mg 2x1 for 3 days
Ivermectin	150–200 µg/kg SD
Pyrantel pamoate	10 mg/kg SD

Preferred treatment:

Albendazole 400 mg single dose

Management of Complications

Complication	Management
Intestinal obstruction	Nasogastric decompression, surgery if severe
Biliary ascariasis	ERCP extraction
Pancreatitis	Supportive care
Appendicitis	Surgical intervention