Ascariasis: Causes, Symptoms, Diagnosis, and Prevention

~Introduction

Ascariasis is a parasitic infection of the small intestine caused by the roundworm Ascaris lumbricoides, one of the most common human intestinal parasites in the world. It is estimated that more than 800 million to 1.2 billion people are infected globally, with the highest prevalence in tropical and subtropical regions where sanitation is poor.

The disease is part of a group of infections known as soil-transmitted helminthiases, which also includes infections by Trichuris trichiura (whipworm) and Ancylostoma duodenale/Necator americanus (hookworms). Although many cases are asymptomatic, heavy infestations can lead to malnutrition, intestinal blockage, impaired growth in children, and even death.

~History and Background

The presence of Ascaris worms in humans has been documented for thousands of years. Evidence of the parasite has been found in ancient Egyptian mummies, and descriptions appear in the writings of Hippocrates (460–375 BC). Despite advances in medicine, ascariasis remains a major public health problem in many developing countries, particularly in rural areas lacking adequate sanitation.

~Causative Agent

Ascaris lumbricoides is a large intestinal nematode (roundworm). Adult worms are cylindrical, tapering at both ends, and can grow 15–35 cm in length. Females are typically larger than males. Their cream-colored bodies are adapted to life in the human gut, where they feed on partially digested food.

~Epidemiology

Ascariasis is distributed worldwide but is most common in:

Asia (India, China, Southeast Asia)
Africa
Latin America
Pacific Islands

Risk factors include:

Poor sanitation (open defecation)
Contaminated water or food
Warm, humid climates favorable for egg survival in soil
Children playing in contaminated environments

The World Health Organization (WHO) identifies school-aged children as the group most affected, due to frequent soil contact and immature immune defenses.

~Life Cycle of Ascaris lumbricoides

Understanding the life cycle is key to grasping how infection occurs and spreads.

Eggs in the environment – Female worms in the human intestine can produce 200,000 eggs per day, which are passed in feces. Fertilized eggs require 2–4 weeks in moist, warm soil to become infective.
Ingestion – Humans become infected by swallowing infective eggs from contaminated food, water, or hands.
Larval migration – After hatching in the small intestine, larvae penetrate the intestinal wall and enter the bloodstream.
Lung phase – Larvae travel via the bloodstream to the lungs, break into the alveoli, ascend the respiratory tract, and are swallowed back into the digestive tract.
Adult stage – Back in the small intestine, larvae mature into adults over 2–3 months.
Egg production – Adults live for about 1–2 years, continuing the cycle.

This pulmonary migration is characteristic and explains some of the respiratory symptoms of ascariasis.

~Modes of Transmission

Transmission occurs fecal-orally:

Eating raw vegetables washed with contaminated water
Drinking contaminated water
Handling soil containing infective eggs and touching the mouth
Poor hygiene after defecation

It is not transmitted directly from person to person without environmental contamination.

~Pathogenesis

The disease mechanisms of ascariasis depend on:

Worm load (number of worms)
Stage of infection (larval migration vs. intestinal stage)
Host immune response

During larval migration, tissue damage occurs in the liver and lungs, causing inflammation and hypersensitivity reactions. In the intestinal stage, worms can compete for nutrients, physically obstruct the intestines, and migrate to other parts of the body, causing complications.

~Clinical Manifestations

The symptoms vary depending on worm burden and stage of infection.

1. Early Stage (Larval Migration)

Often asymptomatic
In some cases, Löffler’s syndrome: transient pneumonia with fever, cough, wheezing, and eosinophilia
Chest X-ray may show fleeting lung infiltrates

2. Intestinal Stage

Mild infection: usually no symptoms
Moderate to heavy infection:
- Abdominal discomfort
- Nausea, vomiting
- Malnutrition and weight loss
- Impaired growth and cognitive development in children
- Diarrhea or constipation

3. Complications

Intestinal obstruction: common in children; worms form a tangled mass
Biliary ascariasis: migration into bile ducts, causing jaundice or cholangitis
Pancreatitis: worms block the pancreatic duct
Appendicitis: rare, if worms enter appendix
Peritonitis: from intestinal wall perforation

~Diagnosis

Diagnosis is straightforward in most cases.

1. Stool Examination

Microscopy: detection of fertilized or unfertilized eggs
Eggs are thick-shelled and golden brown with a bumpy surface
Concentration techniques can improve detection

2. Imaging

Ultrasound: useful for detecting worms in biliary or pancreatic ducts
X-rays: may reveal intestinal obstruction or worm shadows
CT/MRI: rarely needed unless complications are suspected

3. Blood Tests

Eosinophilia may be seen during larval migration
Not specific but supportive

~Treatment

Treatment is effective, simple, and inexpensive.

1. Anthelmintic Medications

Albendazole – single 400 mg oral dose (first choice)
Mebendazole – 100 mg twice daily for 3 days, or single 500 mg dose
Pyrantel pamoate – alternative, especially in children
Ivermectin – sometimes used in mixed infections

2. Management of Complications

Intestinal obstruction: may require nasogastric decompression, IV fluids, and in severe cases, surgery
Biliary or pancreatic ascariasis: endoscopic removal (ERCP) may be necessary

Note: In heavy infections, treatment should be cautious, as killing many worms at once can worsen obstruction.

~Prevention and Control

Prevention strategies focus on breaking the fecal–oral transmission cycle.

1. Sanitation

Proper disposal of human feces
Access to clean toilets and sewage systems

2. Safe Food and Water

Washing vegetables and fruits thoroughly
Drinking boiled or filtered water
Avoiding raw produce from unsafe sources

3. Personal Hygiene

Handwashing with soap before eating and after defecation
Keeping fingernails short and clean

4. Public Health Measures

Mass drug administration (MDA): WHO recommends periodic deworming of at-risk populations, especially school-aged children, in endemic areas.
Health education campaigns to change hygiene behaviors

~Global Impact

Ascariasis has a major burden in low-income countries:

Childhood growth retardation: chronic infection reduces nutrient absorption
School performance: infections impair concentration and energy levels
Economic losses: decreased productivity due to illness

According to WHO estimates:

More than 60,000 deaths occur annually from complications, mostly in children
The highest prevalence is in rural communities dependent on agriculture, where use of untreated human feces as fertilizer is common

~Recent Advances in Research

Recent studies are exploring:

Improved diagnostics – molecular techniques like PCR to detect low-intensity infections
Vaccine development – targeting parasite antigens to prevent infection
Integrated control programs – combining deworming with water, sanitation, and hygiene (WASH) interventions
Drug resistance monitoring – to ensure effectiveness of current treatments

~Case Study Example

In a rural Indian village, a 7-year-old boy presented with abdominal pain, vomiting, and inability to pass stool. Examination revealed abdominal distension. X-ray suggested intestinal obstruction. Surgical exploration revealed a mass of Ascaris worms blocking the small intestine. The worms were removed, and the child recovered after deworming and nutritional support. This illustrates how neglected sanitation can lead to severe, life-threatening disease.

~Prognosis

With proper treatment, prognosis is excellent. Most patients recover fully, especially if complications are avoided. However, reinfection is common in endemic areas unless sanitation and hygiene are improved.

~Conclusion

Ascariasis remains one of the most common parasitic infections worldwide, primarily affecting impoverished communities with inadequate sanitation. Although often asymptomatic, heavy infections can cause significant morbidity, particularly in children. Effective treatment exists, but prevention requires sustained public health measures—clean water, proper sanitation, hygiene education, and regular deworming.

By combining medical treatment with improvements in living conditions, ascariasis could be drastically reduced, if not eliminated, in future generations.

Health Lines

Friday, August 15, 2025

Ascariasis