Basics
Description
Ascaris lumbricoides is a large parasitic nematode (roundworm), 15-40 cm in length, which infects humans via eggs found in soil.
Epidemiology
- Geographic distribution: South America, sub-Saharan Africa, China, and East Asia
- All ages may be affected; however, children are more frequent hosts owing to oral behavior and tend to have a higher worm burden.
- Ascariasis is more common where sanitation is poor and population is dense.
- Eggs are viable in the soil for more than 6 years in temperate climates.
- It is the most prevalent helminth infection in the world.
- ~1/6 of the world's population is infected.
- 8-15% of infections are symptomatic.
- 120-220 million cases
- Mostly moderate and heavy worm loads
General Prevention
Infection control
- Sanitary disposal of human excrement, not using human feces as fertilizer, and hand washing has the potential to eliminate this infection.
- In communities with high transmission of Ascaris, community-wide mass drug delivery of anthelmintics is effective in controlling morbidity.
Pathophysiology
- Fertilized eggs are ingested from soil contaminated with human feces.
- Larvae hatch in the small intestine and migrate to cecum and colon.
- Larvae invade the mucosa into the venous system and travel to the portal circulation, inferior vena cava, and finally, pulmonary capillaries.
- During migration through the pulmonary vessels, an eosinophilic response is evoked.
- Larvae penetrate the alveoli, are expelled by coughing, and swallowed back (days 10-14).
- Larvae become adult worms in the small intestine (day 24).
- Female worms excrete up to 200,000 eggs per day.
- Ingestion to excretion takes 2-3 months.
- Once in soil, fertilized eggs require 2-3 weeks of incubation in soil to become infectious and restart cycle.
Etiology
Children commonly acquire this infection from playing in dirt contaminated with Ascaris eggs.
Commonly Associated Conditions
- This infection may be associated with other soil-transmitted helminths:
- Hookworm (Necator americanus, Ancylostoma duodenale)
- Trichuris trichiura
- Strongyloides stercoralis
- Toxocara canis
Diagnosis
History
- Gastrointestinal symptoms include the following:
- Abdominal distention
- Pain
- Nausea
- Diarrhea
- Decreased appetite
- In the chronic phase, ascariasis is associated with the following:
- Growth stunting
- Cognitive delays
- Severe respiratory symptoms during the pulmonary migratory stage, when larvae cause an inflammatory response (L ¶effler syndrome), characterized by the following:
- Dyspnea
- Cough
- Fever
- Shifting pulmonary infiltrates
- Eosinophilia
- Severe presentation during the intestinal phase, when symptoms are due to the presence of worms:
- Pain
- Obstruction (2 per 1,000)
- Peritonitis from perforation
- Biliary colic, hepatitis, or pancreatitis from blockages due to worms
- History of passage of large worms in the stool or vomitus is suggestive of ascariasis.
- History of wheezing may precede passage of worms by 2-3 months.
Physical Exam
- Chest: may have rales or wheezing if Ascaris larvae are in the lungs
- Abdomen
- Distended
- Auscultate and palpate for signs of obstruction or perforation.
Diagnostic Tests & Interpretation
Lab
- Microscopic examination of stool specimens will demonstrate the characteristic ascaris eggs (round with thick shell).
- During the pulmonary phase, may have peripheral eosinophilia and larvae in sputum, but negative stool examinations
- Serologic tests are unnecessary and are poorly specific to the diagnosis.
Imaging
- Chest radiograph, if cough is present
- Abdominal imaging, if abdominal signs or symptoms of obstruction or perforation
Differential Diagnosis
Ascariasis should be considered in the differential diagnosis when a patient presents with pneumonia, peripheral eosinophilia, and/or intestinal obstruction in returned traveler or resident from an endemic area.
Treatment
Medication
First Line
- Oral
- Albendazole
- 400 mg, single dose
- WHO recommends 200 mg single dose for children <1 year old.
- Mebendazole
- 100 mg, b.i.d. for 3 days or 500 mg once
- Ivermectin
- 150-200 mcg/kg, single dose
- Alternatives (oral):
- Pyrantel pamoate
- 11 mg/kg to max 1 g per day for 3 days
- Piperazine citrate
- 75 mg/kg/24 h for 2 days; maximum, 3.5 g
- Has been used historically for cases of intestinal obstruction (causes worm paralysis), but it is no longer available in the United States
Surgery/Other Procedures
Surgery or endoscopic retrograde cholangiopancreatography may be required for severe intestinal or biliary tract obstruction.
Ongoing Care
Follow-up Recommendations
- Treatment is highly effective.
- Reexamination of stool specimens 2 weeks after therapy can be considered but is not essential.
- Reinfection is common in endemic areas and has led to mass drug administration programs.
Patient Monitoring
Warn parents about passage of worms in stool with treatment.
Prognosis
- Once intestinal infection is detected and treated, the prognosis is excellent.
- If obstructive or respiratory complications have occurred, the prognosis is less favorable.
- The case fatality rate in cases with complications is up to 5%, most from obstruction.
Complications
- Bronchopneumonia may be seen during the pulmonary migrational stage, producing fever, cough, dyspnea, wheeze, eosinophilia, and pulmonary infiltrates (L ¶effler syndrome).
- Heavy infestations may cause abdominal pain, malabsorption, and growth failure.
- Children may experience obstruction (ileocecal), malabsorption, or intussusception.
- Perforation or migration into the appendix, biliary, or pancreatic ducts may rarely occur.
- Hepatitis, acute cholecystitis, or pancreatitis can occur. Liver abscess can occur if intrahepatic ducts are obstructed.
Additional Reading
- American Academy of Pediatrics. Ascaris lumbricoides infections. In: Pickering LK, Baker CJ, Kimberlin DW, et al, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012:239-240.
- Capello M, Hotez PJ. Intestinal nematodes. In: Long S, Pickering L, Prober C, eds. Principles and Practice of Pediatric Infectious Diseases. 3rd ed. Churchill Livingstone/Elsevier; 2008:1296-1298.
- Centers for Disease Control and Prevention. Parasites-ascariasis. http://www.cdc.gov/parasites/ascariasis/. Accessed November 24, 2013.
- Dold C, Holland CV. Ascaris and ascariasis. Microbes Infect. 2011;13(7):632-637. [View Abstract]
- Hall A, Hewitt G, Tuffrey V, et al. A review and meta-analysis of the impact of intestinal worms on child growth and nutrition. Matern Child Nutr. 2008;4(Suppl 1):118-236. [View Abstract]
- O'Lorcain P, Holland CV. The public health importance of Ascaris lumbricoides. Parasitology. 2000;121(Suppl):S51-S71. [View Abstract]
- World Health Organization. Intestinal worms. http://www.who.int/intestinal_worms/en/. Accessed November 24, 2013.
Codes
ICD09
ICD10
- B77.9 Ascariasis, unspecified
- B77.0 Ascariasis with intestinal complications
- B77.81 Ascariasis pneumonia
- B77.89 Ascariasis with other complications
SNOMED
- 50982003 Infection by Ascaris lumbricoides (disorder)
- 1082721000119101 Pneumonia due to Ascaris (disorder)
FAQ
- Q: What are the long term effects of untreated Ascaris infection in children?
- A: Growth stunting and cognitive delays are the most common long-term effects of untreated infections. Given the prevalence of this infection in the world, this is a major cause of morbidity in the world.