Approach

In endemic regions of Asia, Africa, and South America, most patients with ascariasis are asymptomatic and unaware of their infection. Notable exceptions are patients with eosinophilic pneumonitis (Loeffler syndrome) or obstructive complications involving the gastrointestinal or hepatobiliary tracts.[23]​ However, certain patients will observe the passage of adult worms and seek medical attention. Other patients may present with anxiety or panic over the possibility of harboring worms.

Clinical evaluation

If the consultation is taking place outside an endemic country, establishing risk factors, such as recent travel to or residence in a developing country, or adoption of the patient from a country where ascariasis is endemic, is important.[24] In such patients, asthma-like symptoms may herald early larval migration through the lungs. During this phase, larvae pass from the bloodstream to the alveoli, then migrate up the bronchi and are swallowed. Affected patients are said to have eosinophilic pneumonitis or Loeffler syndrome, and may experience fever, cough, dyspnea, and/or hemoptysis over several weeks. Depending on their burden of infection and degree of allergic hyperreactivity, physical exam may also reveal tachypnea, hypoxia, wheezing, rhonchi, rales, intercostal retractions, and/or urticarial skin lesions.[1][16][25] Allergic and pulmonary symptoms are most likely following the ingestion of large numbers of eggs.[13][25][26] Eosinophilic pneumonitis (Loeffler syndrome) due to Ascaris lumbricoides is more common in people whose exposure is rare or intermittent (e.g., expatriates and residents of places such as Saudi Arabia, where transmission is seasonal or sporadic).

Nonspecific gastrointestinal symptoms, including fullness, abdominal pain, anorexia, dyspepsia, vomiting, and diarrhea, may occur with smaller worm burdens.[1][11][24]​​ Tangled boluses of worms may lodge in the ileocecal area and lead to symptoms typical of small bowel obstruction, including nausea, vomiting, and constipation, plus cramps or colicky abdominal pain. Large worm boluses may lead to partial or complete small bowel obstruction. This occurs more frequently in children and is a major cause of morbidity and mortality due to ascariasis. Small bowel obstruction often presents with fever, emesis, distension, focal or generalized abdominal pain, and reduced or absent bowel sounds. If bowel perforation occurs, hypotension, tachypnea, rebound tenderness, and other manifestations of abdominal sepsis may be seen. Gastrointestinal symptoms are more common in younger children, due to their higher worm burdens and smaller intestinal lumina.[1][11]

In the case of hepatobiliary and/or pancreatic ascariasis, patients may present with symptoms of biliary colic, cholecystitis, acute cholangitis, pancreatitis, or hepatic abscess.[5][27] Physical findings can include fever, right upper quadrant tenderness, hepatomegaly, and jaundice. Hepatobiliary and/or pancreatic ascariasis is more common in adults.

Children with heavy worm burdens, especially in endemic and developing countries, may have their growth stunted.[12] In addition, exam may suggest findings of other nutritional deficiency states, such as kwashiorkor or iron-deficiency anemia (e.g., listlessness, brittle hair, cracked skin, edema, conjunctival pallor). Although these signs and symptoms are not specific to ascariasis, their presence should encourage clinicians to look for ascarids and additional intestinal helminths, especially hookworms, as possible contributing factors in children at risk.[16] The deleterious effect on childhood growth and development is the most insidious and pervasive impact of ascariasis. Some studies have suggested that burdens as low as 10 to 15 worms can cause malabsorption, lactose maldigestion, impaired intestinal permeability, and reduced food intake.[11][28][29] These nutritional effects are a particular problem in children who are already malnourished as a result of dietary deficiencies.

While less frequently studied, appetite loss and weight loss in adults associated with soil-transmitted helminths, including ascarids, have been postulated to negatively affect work productivity. Furthermore, the effects of ascariasis on growth and development in childhood may contribute to decreased adult productivity.[10][24]​​​[30][31]

Initial tests

Stool microscopy is the most reliable way to diagnose ascariasis.​[15][32][33][34]​​​​ It should be ordered for patients suspected of intestinal infection, such as returning travelers, expatriates, children adopted from endemic regions, and those in endemic regions with intestinal obstruction. When present on direct exam or in a concentrated specimen, eggs typically appear as pebbled, yellow-brown spheres or ovals measuring 60 to 70 micrometers.[1] Unfertilized eggs may be more difficult to identify because of their atypical size and appearance.

Due to the large number of eggs produced by each adult female worm, exam of a single stool sample is usually diagnostic. Stool microscopy yields false-negative results, however, in infections with single-sex adults or juvenile worms.[24]​​[25] Egg counts per gram of stool may be used to estimate the burden of infection in a given patient and the density of infection in a community.[1][15][30]​​​[34]​​​[35]

Chest x-ray should be performed in patients suspected of having eosinophilic pneumonitis (Loeffler syndrome): that is to say, patients with new-onset asthma or fever and cough who have recently returned from travel in an endemic region. During larval migration through the lungs, chest x-ray may reveal patchy pulmonary infiltrates.

An abdominal x-ray should be performed in patients with suspected intestinal obstruction from areas with endemic ascariasis. Patients with intestinal obstruction may have air fluid levels or multiple linear images of worms within the obstructive bolus.

Subsequent tests

Sputum and gastric aspirate microscopy may reveal larvae measuring 1 to 2 mm during larval migration through the lungs. Sputum may also contain larvae or Charcot-Leyden crystals.[1]

Complete blood count may reveal eosinophilia during the migratory phase, and low hemoglobin may reflect concurrent hookworm infection or nutritional deficiency. This test may complement sputum/gastric aspirate microscopy and chest x-ray in patients suspected of eosinophilic pneumonitis (Loeffler syndrome).

Adult worms may also be seen on barium follow-through, as linear filling defects outlined by contrast media, or, if the worms themselves ingest barium, as curved linear densities within the intestinal lumen. This investigation is commonly done on patients who have unexplained abdominal pain or weight loss. Ascarids may be an incidental or an expected finding depending on the differential diagnoses for that patient.

If abdominal x-ray suggests small bowel obstruction, an abdominal ultrasound, contrast study, or abdominal CT scan may reveal the cause of the obstruction to be a mass of adult worms in the gastrointestinal tract or single worms obstructing the hepatobiliary tree.[36][37][38][39] For patients thought to have hepatobiliary tree worms, an endoscopic retrograde cholangiopancreatography (ERCP) can then be performed to confirm the diagnosis and to remove them.[40] In resource-limited settings these diagnostic procedures may not be available, and diagnosis would rely on clinical judgment.

Emerging tests

Antibodies to Ascaris lumbricoides have been used in epidemiologic studies, but are rarely (if ever) used to diagnose individual infections. Migrating larvae are associated with elevated serum IgE levels, tissue eosinophilia, and mastocytosis. Interleukin (IL)-4, IL-5, and IL-13 may be preferentially released by CD4+ T cells as part of a Th2-mediated inflammatory response.[13][15] Urine-based gas liquid chromatography techniques for the diagnosis of ascariasis have also been developed, although their use remains limited to research.[41]

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