History
Most individuals are asymptomatic, even in communities where the prevalence is high. The most common manifestation is asymptomatic passage of an adult worm via the rectum, particularly in children in endemic areas. Rarely, an adult in a nonendemic area who is asymptomatic passes a worm via the rectum and may not be able to recount any significant exposure history. Less frequently, a worm migrates to the oropharynx and is coughed out. Ascaris eggs are often found in the stools of asymptomatic individuals in endemic areas. Some individuals with known significant worm burdens report anorexia, abdominal discomfort, and diarrhea; however, these symptoms cannot be directly attributed to ascariasis.
Pulmonary ascariasis
Symptoms develop 1-2 weeks after infection; they vary from none to life-threatening (rare), depending on sensitization or considerable migrating worm burden. Symptoms include chest pain (burning, aggravated by cough), cough (dry), dyspnea, fever, sputum (may be blood-tinged), and wheezing.
A massive infestation can lead to Löeffler syndrome (ie, transient eosinophilia, transient lung infiltrates); ascariasis remains the most common cause of this syndrome worldwide. In areas of continuous transmission, pulmonary symptoms tend to be less evident. Urticaria is present in 15% of patients and usually develops in the first 4-5 days of illness. Symptoms last 5-10 days but have been reported to last weeks in severe cases.
Intestinal obstruction
Partial or complete obstruction secondary to an entangled worm bolus can occur at any age; however, 85% of cases occur in children aged 1-5 years and most occur at terminal ileum, although they have been rarely reported in the duodenum. The worm bolus may also cause intussusception or volvulus. [17] Severe, sharp, colicky abdominal pain with associated vomiting predominates. The vomit may contain worms. Other common symptoms include fever and diarrhea. Depending on the duration of symptoms and the presence of comorbid conditions (eg, malnutrition), the patient may present with or progress rapidly to sepsis, sepsis syndrome, and septic shock.
Complete obstruction may begin subsequent to the administration of an antihelminthic, particularly in the setting of acute abdominal pain or partial bowel obstruction. Specific concern surrounds the administration of pyrantel pamoate, which causes a spastic paralysis of the worms and accentuates the potential for an obstructive bolus. Complete obstruction has also been reported with piperazine (flaccid paralysis of worms) and mebendazole (single large dose).
In endemic countries, ascariasis accounts for 5-35% of intestinal obstruction cases, particularly in children.
Hepatobiliary and pancreatic ascariasis and other GI diseases
Migrating adult worms (most common), worm fragments, or eggs can cause acalculous cholecystitis, ascending cholangitis, appendicitis, biliary colic, gastric hemorrhage, granulomatous peritonitis, liver abscess, Meckel diverticulum inflammation, obstructive jaundice, pancreatitis, and peritonitis and/or peritoneal granulomatosis (ie, ductal and/or intestinal perforation or migration through perforation secondary to typhoid or tuberculosis). Imaging with CT scanning and ultrasonography reveals the etiology in many cases. The etiology may not be apparent until endoscopic retrograde cholangiopancreatography (ERCP) or surgery is performed. [18]
Extra-GI conditions
Worms may migrate to the upper respiratory tract (ie, throat, nose, lacrimal ducts, and inner ear); to the vagina; and to the kidney, ureter, and bladder (via the vagina).
Experimental studies report that the migrating larvae can enter many tissues, including the brain, kidney, and lymph nodes, but cannot survive. Several case reports have suggested encephalopathy secondary to Ascaris larvae.
Physical
Pulmonary ascariasis
In most cases, the lungs are clear or wheezing may be observed. In more severe cases, including ascaris pneumonia, a fever (≤ 102ºF), rales, and wheezing may be observed. Dullness to percussion and bronchial breathing are rare, even in severe cases. Signs may persist for several days.
Intestinal obstruction or partial obstruction
The patient appears ill, often with abnormal vital signs (eg, tachycardia, fever) and may be actively vomiting and reporting severe abdominal pain. The abdomen is moderately-to-severely tender in a diffuse or localized pattern, usually on the right side. A palpable mass (worm bolus) may be observed. Assess for increasing pain, tachycardia, tachypnea, fever, abdominal tenderness, and vomiting, all of which may indicate progression of the obstruction, the development of sepsis, or perforation.
Hepatobiliary disease
Upon presentation, the patient may appear ill, may have abnormal vital signs (eg, tachycardia, tachypnea, fever), and may be actively vomiting. These patients usually report abdominal pain (mild, moderate, or severe). Depending on the pathology, the symptoms may rapidly progress rapidly over hours, as follows:
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Biliary colic: Fever and jaundice are often absent; the worms are usually in the ampullary orifice, and removal results in rapid improvement.
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Acalculous cholecystitis: Pain and tenderness in right upper quadrant are reported. Jaundice may or may not be present. The pain often radiates to the back on the right (see Cholecystitis).
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Ascending cholangitis: The patient is usually critically ill with fever, tachycardia, tachypnea, jaundice, severe pain, and severe right upper quadrant or diffuse abdominal tenderness. The liver is tender and enlarged.
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Pancreatitis: Moderate or severe pain and tenderness in the epigastrium and the left upper quadrant is reported, along with associated vomiting of varying intensity. The pain often radiates to the back on the left (see Pancreatitis and Pancreatic Pseudocyst).
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Hepatic abscess: Severe pain and tenderness is reported in the right upper quadrant. The liver is tender and enlarged.
Causes
Ascariasis is caused by ingestion of an embryonated A lumbricoides egg or embryonated A suum egg (see Pathophysiology). Whether A suum and A lumbricoides are separate species remains controversial; however, evidence suggests that they may be distinct entities.
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The roundworm Ascaris lumbricoides causes ascariasis. Worms can reach 10-30 cm in length. Clinical disease results from effects of pulmonary larval migration, intestinal obstruction, or migration through the biliary tree.
Tables
Parasite* |
Disease |
Prevalence |
A lumbricoides |
Common roundworm infection, ascariasis |
800 million to 1.4 billion |
T trichiura |
Whipworm infection, trichuriasis |
600 million to 1 billion |
Necator americanus and Ancylostoma duodenale |
580 million to 1.2 billion |
|
Strongyloides stercoralis |
Threadworm infection, strongyloidiasis |
30-300 million |
Enterobius vermicularis |
Pinworm infection |
4-28% of children |
Toxocara canis and Toxocara cati |
Visceral larva migrans and ocular larva migrans |
2-80% of children |
*All major parasites are found in tropical, subtropical, and temperate climates. |
||
Minor Parasite |
Disease |
Distribution |
Ancylostoma braziliense |
Costal regions worldwide |
|
Uncinaria stenocephala |
Cutaneous larva migrans |
Costal regions worldwide |
Ancyclostoma canium |
Eosinophilic enteritis |
Australia |
Ancylostoma ceylanicum |
Hookworm infection |
Asia |
Oesophagostomum bifurcum |
Nodular worm infection |
North America |
Strongyloides fuelleborni |
Swollen belly syndrome |
West Africa |
Ternidens diminutus |
False hookworm infection |
Southern Africa |
