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Ascaris Infection

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What is an ascaris infection? 

An ascarid  is a worm that lives in the small intestine. Infection with ascarids  is called ascariasis (ass-kuh-rye-uh-sis). Adult female worms can grow over 12 inches in length, adult males are smaller.

How common is ascariasis?

Ascariasis is the most common human worm infection. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor. Children are infected more often than adults. In the United States, infection is rare, but most common in rural areas of the southeast.

What are the signs and symptoms of an ascaris infection? 

Most people have no symptoms. If you are heavily infected, you may have abdominal pain. Sometimes, while the immature worms migrate through the lungs, you may cough and have difficulty breathing. If you have a very heavy worm infection, your intestines may become blocked. 

How is an ascaris infection spread? 

Ascarid eggs are found in the soil. Infection occurs when a person accidently ingests (swallows) infective ascarid eggs. Once in the stomach, larvae (immature worms) hatch from the eggs. The larvae are carried through the lungs then to the throat where they are then swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms lay eggs that are then passed in feces; this cycle will take between 2-3 months. 

Pigs can be infected with ascarids. Occasionally, a pig ascarid infection can be spread to humans; this occurs when infective eggs, found in the soil and manure, are ingested. Infection is more likely if pig feces is used as fertilizer in the garden; crops then become contaminated with ascarid eggs. 

How can I get ascariasis? 

You or your children can become infected after touching your mouth with your hands contaminated with eggs from soil or other contaminated surfaces. 

What should I do if I think I have ascariasis? 

See your health care provider. 

How is diagnosis of ascaris made? 

Your health care provider will ask you to provide stool samples for testing. Some people notice infection when a worm is passed in stool or is coughed up. If this happens, bring in the worm specimen to your health care provider for diagnosis. There is no blood test used to diagnose an ascarid infection. 

What is the treatment for ascariasis? 

In the United States, ascaris infections are generally treated for 1-3 days with medication prescribed by your health care provider. The drugs are effective and appear to have few side-effects. Your health care provider will likely request additional stool exams 1 to 2 weeks after therapy; if the infection is still present, treatment will be repeated. 

I am pregnant and have just been diagnosed with ascariasis. Can I be treated? 

Infection with ascarid worms is generally light and is not considered an emergency. Unless your infection is heavy, and your health may be at risk, treatment is generally postponed until after delivery of the baby. 

How can I prevent infection with ascarids? 

  • Avoid contacting soil that may be contaminated with human feces. 
  • Do not defecate outdoors. 
  • Dispose of diapers properly. 
  • Wash hands with soap and water before handling food. 
  • When traveling to countries where sanitation and hygiene are poor, avoid water or food that may be contaminated. 
  • Wash, peel or cook all raw vegetables and fruits before eating. 

Should I be concerned about spreading infection to the rest of my household? 

No. Infection is not spread from person to person. 


Symptoms of Ascariasis 

General information about symptoms of Ascariasis:  The symptom information on this page attempts to provide a list of some possible symptoms of Ascariasis. This symptom information has been gathered from various sources, may not be fully accurate,  and may not be the full list of  symptoms of Ascariasis. Furthermore, symptoms of Ascariasis may vary on  an individual basis for each patient. Only your doctor can provide adequate diagnosis of symptoms and whether they are indeed symptoms of Ascariasis. 

List of symptoms of Ascariasis: The list of symptoms mentioned in various sources for Ascariasis includes: 

  • No symptoms 
  • Stage 1: worm larvae in the bowels attach to bowel walls 
  • Stage 2: worm larvae migrate into the lungs: 

                   * Fever 
                   * Wheezing 
                   * Coughing 

  • Stage 3: worms enter the small intestine and mature into worms and remain there to feed 

                   * Abdominal symptoms 
                   * Abdominal discomfort 
                   * Malabsorption 

  • Intestinal blockage - may be partial or complete 

                   * Partial intestinal blockage 
                   * Total intestinal blockage 
                   * Severe abdominal pain 
                   * Vomiting 
                   * Restlessness 
                   * Disturbed sleep 

  • Worm in stool 
  • Worm in vomit 

Symptoms of Ascariasis:  Most people have no symptoms.  If you are heavily infected, you may have abdominal pain. Sometimes, while the immature worms migrate through the lungs, you may cough and have difficulty breathing. If you have a very heavy worm infection, your intestines may become blocked. 

A  few worms  in the intestine may cause no symptoms or may give rise only to vague or intermittent abdominal pain. Heavy infection may cause partial or complete blockage of  the intestine resulting in severe abdominal pain, vomiting, restlessness, and disturbed sleep.  The heavier or greater  the worm infection,  the more severe  the symptoms  are likely to be. Occasionally, the first sign  of infection may be the presence of a worm  in vomit or in  the stool. 

More symptoms of Ascariasis:  In addition to the above information, to  get a full picture of the possible symptoms of this condition and its related conditions, it may be necessary to examine symptoms  that may be caused  by complications of Ascariasis, underlying causes of Ascariasis, associated conditions for Ascariasis, risk factors for Ascariasis,  or other related conditions. 


Ascaris Infection - Diagnosis 

The  diagnosis is usually incidental when the host passes a worm in the stool or vomit. Stool samples for ova and parasites will demonstrate Ascaris eggs. Larvae may be found in gastric or respiratory secretions in pulmonary disease. Blood counts may demonstrate peripheral eosinophilia. On X-ray, 15-35 cm long filling defects, sometimes with whirled appearance (bolus  of worms).

Diagnostic Findings 

Microscopic identification of eggs in the  stool is the most common method  for diagnosing intestinal ascariasis. The recommended procedure is as follows: 
  • Collect  a stool specimen. 
  • Fix the specimen in 10% formalin. 
  • Concentrate using the formalin–ethyl acetate sedimentation technique. 
  • Examine a wet mount of the sediment. 

Where concentration procedures are not available, a direct wet mount examination of the specimen  is adequate for detecting moderate to heavy infections. For quantitative assessments of infection, various methods such as the Kato-Katz can be used. Larvae can be identified in sputum or gastric aspirate during the pulmonary migration phase (examine formalin-fixed organisms for morphology). Adult worms are occasionally  passed in the stool or through the mouth or nose and are recognizable by their macroscopic characteristics. 

Ultrasound :

Macroscopic Findings 

  • Fertilized eggs are rounded, have a thick shell, with an external mammillated layer that  is often stained brown by bile. In some cases, the outer layer is absent. Size: approximately 60 µm in diameter when spherical, and up to 75 µm when ovoid. 
  • Unfertilized eggs are elongated and larger (up to 90 µm in length); their shell is thinner; and their mammillated layer is more variable, either with large protuberances or practically none; these eggs contain mainly a mass of refractile granules. 
  • Fertilized Ascaris egg, still at the unicellular stage. Eggs are normally at  this stage when passed  in the stool. Complete development of the larva requires 18 days under favorable conditions. 
  • Unfertilized and fertilized eggs 
  • Unfertilized egg. Prominent mammillations of outer layer. 
  • Fertilized egg. The embryo can be distinguished inside the egg. 
  • Unfertilized egg with no outer mammillated layer (decorticated). 
  • Three fertilized eggs (one decorticated, on the right) of Ascaris lumbricoides. 


  • Two fertilized eggs from the same patient, where embryos have begun  to develop (this happens when the stool sample is not processed for several days without refrigeration). The embryos in early stage of division (4  to 6 cells) can be clearly seen. 
  • Egg containing a larva, which will be infective if ingested. 
  • Larva hatching from an egg. 



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