Roundworm (Ascariasis): Symptoms, Treatment & Prevention

What Is Roundworm (Ascariasis)?

Ascariasis is an intestinal infection caused by the parasitic roundworm Ascaris lumbricoides. It is the most common human worm infection worldwide, affecting approximately 800 million to 1.2 billion people, primarily in tropical and subtropical regions where sanitation is inadequate. The adult worms live in the small intestine and can grow 10-30 centimeters long.

Roundworm infection, medically known as ascariasis, is caused by a large parasitic worm that resembles an earthworm in appearance. The worms are typically light brown to white in color and can reach lengths of up to 35 centimeters, making them among the largest intestinal parasites that infect humans. Despite being one of the most common parasitic infections globally, ascariasis is relatively rare in countries with modern sanitation systems and clean water supplies.

The infection occurs when a person accidentally swallows Ascaris eggs, typically through contaminated food or water. Once inside the body, the eggs hatch in the intestines and undergo a complex life cycle that includes migration through the lungs before the adult worms establish themselves in the small intestine. This migration phase can cause respiratory symptoms in some individuals, while the intestinal phase may cause digestive symptoms or no symptoms at all.

Understanding how roundworm infection occurs, its symptoms, and available treatments is important for anyone traveling to or living in areas where the infection is common. The good news is that ascariasis is highly treatable with effective medications, and proper hygiene practices can prevent infection entirely.

Who Gets Roundworm Infection?

Ascariasis primarily affects people living in tropical and subtropical regions where sanitation infrastructure is limited or absent. The highest prevalence is found in sub-Saharan Africa, Southeast Asia, Central and South America, and parts of the Western Pacific region. Children between the ages of 5 and 15 are most commonly affected, as they are more likely to play in contaminated soil and have less developed hygiene habits.

In developed countries, roundworm infections are relatively rare and typically occur in travelers returning from endemic areas, immigrants from high-prevalence regions, or individuals living in rural areas with poor sanitation. Agricultural workers who come into contact with soil fertilized with human waste may also be at increased risk.

Medical Classification

Ascariasis is classified under the International Classification of Diseases (ICD-10) with the code B77. The SNOMED CT code for ascariasis is 2991000, and the MeSH identifier is D001196. Understanding these classifications helps healthcare providers accurately diagnose and track the condition.

What Are the Symptoms of Roundworm Infection?

Many roundworm infections cause no symptoms, with the worm typically discovered in stool. When symptoms occur, they may include abdominal pain, nausea, loss of appetite, fatigue, and visible worms in stool. During the larval migration phase through the lungs, coughing and breathing difficulties may occur. Severe infections can cause intestinal obstruction and malnutrition.

The symptoms of ascariasis vary considerably depending on the number of worms present in the body, the stage of infection, and the individual's overall health status. Many people with light infections experience no symptoms at all, and the first sign of infection may be seeing an adult worm in their stool. This can be alarming but is actually a helpful indicator that infection is present.

The life cycle of Ascaris lumbricoides involves two distinct phases that can each produce different symptoms. After eggs are swallowed, they hatch in the small intestine and the larvae penetrate the intestinal wall, entering the bloodstream. From there, they travel to the lungs, where they can cause respiratory symptoms before being coughed up and swallowed again, finally maturing into adult worms in the intestines.

Respiratory Symptoms (Larval Migration Phase)

When roundworm larvae migrate through the lungs, some people experience what is known as Löffler syndrome. This typically occurs 4-16 days after swallowing the eggs and can include coughing (sometimes with blood-tinged sputum), wheezing, shortness of breath, and low-grade fever. These symptoms usually resolve within one to two weeks as the larvae complete their migration. In rare cases, a heavy larval load can cause more severe pneumonia-like symptoms.

Intestinal Symptoms

Once adult worms establish themselves in the small intestine, they can cause various digestive symptoms. Common complaints include vague abdominal discomfort or pain, particularly around the belly button area, nausea, loss of appetite, and occasional episodes of diarrhea. Children may become irritable and have difficulty sleeping. In some cases, adult worms may be visible in vomit or stool.

Symptoms of Severe Infection

Heavy worm burdens can lead to serious complications. When large numbers of worms are present, they can form tangled masses that physically block the intestine, causing a condition called intestinal obstruction. This is a medical emergency characterized by severe abdominal pain, vomiting (sometimes containing worms), abdominal distension, and inability to pass stool or gas.

Adult worms can also migrate to unusual locations, including the bile ducts (causing biliary ascariasis with symptoms similar to gallbladder disease), the pancreatic duct (causing pancreatitis), the appendix (causing appendicitis), or even exit through the nose or mouth during vomiting or coughing episodes.

Nutritional Effects

Chronic roundworm infection, particularly in children, can lead to significant nutritional problems. The worms compete with their host for nutrients, potentially causing deficiencies in vitamin A, protein, and other essential nutrients. Signs of nutritional deficiency include fatigue, weakness, pale appearance, poor concentration, and in children, growth retardation and cognitive impairment. These effects are most significant in areas where food security is already a concern.

When Should You See a Doctor for Roundworm?

See a doctor if you notice worms in your stool, experience persistent abdominal pain or digestive symptoms, or have returned from travel to areas with poor sanitation. Seek immediate medical care for severe abdominal pain, vomiting with worms, signs of intestinal obstruction, or severe respiratory symptoms. Most cases can be diagnosed and treated at a regular healthcare facility.

Deciding when to seek medical care for suspected roundworm infection depends on the severity of symptoms and individual circumstances. In most cases, roundworm infection is not an emergency, but prompt diagnosis and treatment can prevent complications and stop the spread of eggs in the environment.

If you discover a worm in your stool or vomit, this is a clear indication that you should see a healthcare provider for diagnosis and treatment. While finding a worm can be disturbing, it actually provides valuable diagnostic information. If possible, preserve the worm in a clean container with water or take a photograph to show your doctor. This can help confirm the diagnosis and ensure appropriate treatment.

Situations Requiring Medical Attention

You should contact a healthcare provider if you experience any of the following: visible worms in stool or vomit, persistent abdominal pain or discomfort lasting more than a few days, unexplained nausea, loss of appetite, or weight loss, respiratory symptoms following travel to endemic areas, or if a child is showing signs of malnutrition or growth problems. Healthcare providers can perform simple tests to confirm the diagnosis and prescribe effective treatment.

Emergency Situations

Certain symptoms require immediate medical attention. Severe, colicky abdominal pain accompanied by vomiting and abdominal distension may indicate intestinal obstruction, which requires emergency treatment. Similarly, if worms are visibly emerging from the mouth, nose, or rectum during active expulsion, medical evaluation is needed. Severe respiratory distress during the larval migration phase, though rare, also warrants emergency care.

How Do You Get Infected with Roundworm?

Roundworm infection occurs by accidentally swallowing Ascaris eggs through contaminated food, water, or soil. Common sources include unwashed vegetables grown in contaminated soil, drinking contaminated water, and putting contaminated hands in the mouth. The infection cannot spread directly from person to person, as eggs require time in soil to become infectious.

Understanding how roundworm infection spreads is essential for prevention. The transmission cycle of Ascaris lumbricoides depends entirely on the fecal-oral route, meaning that eggs must be swallowed to cause infection. However, there is an important detail that distinguishes ascariasis from some other parasitic infections: freshly passed eggs are not immediately infectious. They must spend time in warm, moist soil (typically 2-4 weeks) before they become capable of causing infection.

This soil maturation requirement has significant implications for how the infection spreads. It means that direct person-to-person transmission does not occur. You cannot catch roundworm from being near an infected person or from casual contact. Instead, the infection cycle requires eggs to pass out of an infected person's body in feces, contaminate soil, mature in that soil, and then be accidentally ingested by another person.

Common Routes of Transmission

The most common way people become infected is by eating raw vegetables or fruits that have been grown in soil contaminated with human feces (often used as fertilizer in some regions) and not washed thoroughly. Water contaminated with fecal matter can also contain infectious eggs. Children playing in contaminated soil may get eggs on their hands and transfer them to their mouths. Poor handwashing after using the toilet in areas with inadequate sanitation can also lead to environmental contamination and subsequent infection.

The Life Cycle of Roundworm

Understanding the complete life cycle helps explain why certain prevention measures are effective. When a person swallows mature Ascaris eggs, they hatch in the small intestine within hours. The released larvae penetrate the intestinal wall and enter the bloodstream, which carries them to the liver and then to the lungs. This journey takes about 10-14 days.

In the lungs, the larvae mature further, break through into the airways, and are coughed up into the throat. Most are then swallowed, returning to the small intestine where they mature into adult worms. The entire process from egg ingestion to egg-laying adults takes approximately 8-12 weeks. Adult worms can live 1-2 years in the intestine, with each female producing up to 200,000 eggs per day, which pass out in feces to potentially continue the cycle.

Roundworm in Pets

While dogs and cats can harbor their own species of roundworms (Toxocara canis and Toxocara cati), these are different parasites from Ascaris lumbricoides. However, if humans accidentally ingest eggs from animal roundworms, the larvae can migrate through the body causing a condition called visceral larva migrans. These animal roundworm larvae cannot complete their life cycle in humans and typically do not cause intestinal infection, but they can cause inflammation in organs like the lungs, liver, or eyes.

How Is Roundworm Infection Diagnosed?

Roundworm infection is typically diagnosed through stool examination, where eggs or adult worms are identified under a microscope. If you have seen a worm, describing or photographing it can help with diagnosis. Blood tests may show elevated eosinophils (a type of white blood cell), which suggests parasitic infection. In some cases, imaging studies may be needed to assess complications.

Diagnosing roundworm infection is usually straightforward when adult worms have been seen in stool or vomit. In such cases, describing the worm's appearance (size, color, shape) to a healthcare provider or bringing the actual worm for identification can confirm the diagnosis. Digital photographs of passed worms can also be helpful diagnostic tools in the era of telemedicine.

When worms have not been directly observed, healthcare providers typically rely on laboratory testing to confirm the diagnosis. The most common and definitive test is microscopic examination of a stool sample, looking for the characteristic oval-shaped eggs of Ascaris lumbricoides. Because egg production can be intermittent and may not begin until weeks after initial infection, multiple stool samples collected on different days may be necessary for accurate diagnosis.

Stool Examination

The stool examination for roundworm eggs is a simple procedure that can be performed at most medical laboratories. A small amount of stool is mixed with a saline or concentration solution and examined under a microscope. Ascaris eggs have a distinctive appearance – they are oval-shaped with a thick, bumpy outer shell (in fertilized eggs) or a more irregular shape (in unfertilized eggs). An experienced laboratory technician can easily identify these eggs and distinguish them from eggs of other parasites.

Blood Tests

While blood tests cannot definitively diagnose ascariasis, they can provide supportive evidence of parasitic infection. A complete blood count often shows elevated eosinophils – a type of white blood cell that increases in response to parasitic infections and allergic conditions. This eosinophilia is particularly pronounced during the larval migration phase when larvae are passing through the lungs. However, eosinophil levels may be normal in chronic, established infections.

Imaging Studies

In cases where complications are suspected, imaging studies may be helpful. Abdominal X-rays can sometimes reveal the silhouettes of adult worms in the intestine, particularly in heavy infections. Ultrasound can detect worms in the bile ducts or gallbladder, a condition known as biliary ascariasis. CT scans or MRI may be used when other complications are suspected or when the diagnosis remains unclear.

How Is Roundworm Infection Treated?

Roundworm infection is treated with antiparasitic medications, most commonly mebendazole or albendazole. These medications are highly effective, with cure rates exceeding 90%. Treatment typically lasts 1-3 days, after which the worms die and are eliminated from the body within a few days. Pregnant women should consult a doctor before taking these medications.

The treatment of ascariasis is straightforward and highly effective when appropriate medications are used. The World Health Organization (WHO) recommends benzimidazole anthelmintics – specifically albendazole or mebendazole – as first-line treatments for intestinal roundworm infection. These medications work by disrupting the worms' ability to absorb glucose, effectively starving them and causing their death. The dead worms are then naturally expelled from the body in stool.

Mebendazole, available in both tablet and liquid formulations, is typically given as 100 mg twice daily for 3 days, or as a single 500 mg dose. Albendazole is usually given as a single 400 mg dose. Both medications are well-tolerated with minimal side effects, which may include mild abdominal discomfort, nausea, or diarrhea as the worms are expelled. After treatment, it may take several days for all worms to be eliminated from the body.

Treatment Effectiveness

Studies show that both mebendazole and albendazole achieve cure rates of over 90% for ascariasis when taken as directed. In cases of heavy infection, a follow-up stool examination 2-4 weeks after treatment may be recommended to confirm that all worms have been eliminated. If eggs are still present, retreatment may be necessary. In endemic areas, regular deworming programs (typically every 6-12 months) are used to keep infection levels low and prevent complications.

Alternative Medications

For patients who cannot tolerate benzimidazoles or in regions where they are unavailable, alternative treatments include ivermectin (a single dose of 150-200 mcg/kg) or pyrantel pamoate (11 mg/kg as a single dose, up to 1 gram). Ivermectin is particularly useful when multiple parasitic infections are present, as it is effective against a broad range of parasites. However, ivermectin should be used with caution in areas where Loa loa (another parasitic worm) is endemic due to the risk of severe reactions.

Treatment During Pregnancy

Pregnant women who have ascariasis present a special treatment consideration. While the benzimidazole drugs are generally avoided during the first trimester due to theoretical concerns about fetal effects, the WHO advises that treatment may be given during the second and third trimesters when the benefits outweigh the potential risks. Untreated ascariasis during pregnancy can contribute to maternal anemia and nutritional deficiencies that may affect fetal development. Pregnant women should always consult with a healthcare provider to weigh the risks and benefits of treatment.

Children and School Attendance

Children with roundworm infection do not need to be kept home from school or daycare, provided they are feeling well enough to participate. Because roundworm does not spread directly from person to person, there is no risk of transmission to classmates through normal contact. Standard hand hygiene practices should be followed as always, and treatment should be completed as prescribed.

How Can You Prevent Roundworm Infection?

Roundworm infection can be prevented through good hygiene practices: wash hands thoroughly before eating and after using the toilet, wash all fruits and vegetables thoroughly, drink only safe water when traveling to endemic areas, avoid eating raw vegetables where human feces is used as fertilizer, and teach children proper hand hygiene. These simple measures are highly effective at preventing infection.

Preventing roundworm infection relies primarily on breaking the transmission cycle through proper sanitation and hygiene practices. Since the infection requires ingestion of eggs that have matured in contaminated soil, avoiding contact with or ingestion of such contaminated material is the key to prevention. The good news is that these preventive measures are simple, inexpensive, and highly effective.

Personal hygiene forms the foundation of prevention. Handwashing with soap and clean water before eating, before preparing food, and after using the toilet removes any eggs that may have been picked up from the environment. This simple practice can prevent not only ascariasis but many other infectious diseases as well. For children, who may be more likely to put their hands in their mouths after playing, teaching and reinforcing good hand hygiene habits is particularly important.

Food and Water Safety

When traveling to or living in areas where roundworm infection is common, food and water safety becomes especially important. All fruits and vegetables should be thoroughly washed with clean water before eating. Produce that cannot be effectively washed should be peeled before consumption. Vegetables that grow close to or in the soil (such as lettuce, carrots, and root vegetables) carry higher risk if grown in areas where human feces is used as fertilizer.

Water safety is equally important. In areas with potentially contaminated water supplies, drink only bottled water, water that has been boiled for at least one minute, or water that has been treated with appropriate filtration or disinfection methods. Avoid ice unless you are certain it was made with safe water. Be cautious of raw salads or other uncooked foods that may have been prepared with contaminated water.

Environmental Measures

On a community level, proper sanitation infrastructure is the most effective way to prevent roundworm transmission. Access to toilets that safely dispose of human waste prevents environmental contamination with Ascaris eggs. Avoiding the use of untreated human feces as fertilizer eliminates a major transmission route. In endemic areas, community-wide deworming programs combined with health education have proven effective at reducing infection rates.

Travel Precautions

If you are traveling to regions where roundworm infection is common (tropical and subtropical areas with poor sanitation), take extra precautions. Stick to foods that have been thoroughly cooked and are served hot. Peel fruits yourself rather than eating pre-cut fruit. Avoid street food that may have been prepared under unsanitary conditions. Use hand sanitizer when handwashing facilities are not available. Upon returning from travel, if you experience any digestive symptoms or notice anything unusual in your stool, seek medical evaluation.

What Are the Complications of Roundworm Infection?

While most roundworm infections are mild, heavy infections can cause serious complications including intestinal obstruction, biliary obstruction (worms blocking bile ducts), pancreatitis, appendicitis, malnutrition, and growth problems in children. These complications are more common in areas with high infection rates and poor access to medical care.

Although the majority of roundworm infections are asymptomatic or cause only mild symptoms, heavy infections and certain situations can lead to serious complications. Understanding these potential complications helps explain why prevention and prompt treatment are important, particularly in endemic areas where reinfection is common and worm burdens can accumulate over time.

The risk of complications generally correlates with the number of worms present in the body. A person with only a few worms may experience no problems at all, while someone with dozens or hundreds of worms faces significantly higher risks. Children, who often have higher worm burdens relative to their body size, are at greater risk for complications than adults.

Intestinal Obstruction

The most serious complication of ascariasis is intestinal obstruction, which occurs when a large mass of tangled worms physically blocks the passage of food and feces through the intestine. This is a medical emergency that presents with severe abdominal pain, vomiting (sometimes containing worms), abdominal distension, and failure to pass gas or stool. Intestinal obstruction requires immediate medical attention and may necessitate surgical intervention if it cannot be relieved with medication.

Biliary and Pancreatic Complications

Adult roundworms can migrate from the intestine into the biliary system (the bile ducts and gallbladder) or the pancreatic duct. This migration can cause biliary colic (severe pain in the upper right abdomen), acute cholangitis (infection of the bile ducts), cholecystitis (gallbladder inflammation), or acute pancreatitis. These conditions cause intense abdominal pain and require urgent medical treatment. Imaging studies such as ultrasound can usually identify worms in these locations.

Nutritional Consequences

Chronic roundworm infection contributes to malnutrition through several mechanisms. The worms compete with their host for nutrients, particularly vitamin A and other micronutrients. They can also cause malabsorption by damaging the intestinal lining. In children, chronic infection has been linked to stunted growth, cognitive impairment, and reduced school performance. These effects are most significant in populations where baseline nutrition is already marginal.

Respiratory Complications

During the larval migration phase, particularly when large numbers of larvae are passing through the lungs simultaneously, significant respiratory symptoms can occur. This ranges from mild cough and wheezing to pneumonia-like illness. In rare cases, particularly in individuals with underlying respiratory conditions, this can lead to respiratory failure requiring intensive care.

What Is the Outlook for Roundworm Infection?

The prognosis for roundworm infection is excellent with proper treatment. Antiparasitic medications cure over 90% of infections within days. Most people recover completely without long-term effects. However, in endemic areas, reinfection is common without improved sanitation. Untreated severe infections can cause serious complications, particularly in children.

For the vast majority of people who receive appropriate treatment, roundworm infection resolves completely with no lasting effects. The antiparasitic medications available today are highly effective, well-tolerated, and widely accessible. After completing a course of treatment, the worms are eliminated and symptoms resolve, typically within days to weeks depending on the initial severity of infection.

The main challenge in endemic areas is not treating individual infections but preventing reinfection. Without improvements in sanitation and hygiene practices, people living in contaminated environments may become reinfected shortly after treatment. This is why public health programs in endemic areas often combine regular mass drug administration with education about hygiene and efforts to improve sanitation infrastructure.

For travelers who acquire infection abroad, the outlook is uniformly excellent. A single treatment course is usually curative, and reinfection is unlikely unless there is continued exposure to contaminated environments. Any nutritional deficits that developed during the infection period resolve with adequate diet once the worms are eliminated.