Potential Pediatric Pulmonary Parasites

Abstract & Commentary

By Phil Fischer, MD, DTM&H

Dr. Fischer is Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN.

Dr. Fischer reports no financial relationships relevant to this field of study.

Synopsis: Respiratory symptoms in immigrants and returned travelers can prompt consideration of several different parasitic pulmonary infections. In October 2010, two U.S.-based journals published case reports and photos of children with hydatid cysts in the lungs. Echinococcosis relates to close contact with dogs and is treatable by a combination of medical and surgical therapies.

Sources: Ludmir J, Valliante WK, Kuskov SI, et al. Picture of the Month: Ruptured hydatid lung cyst. Arch Pediatr Adolesc Med 2010;164:973-975.

Kumar VA, Mehta A, Agara D. Actively motile larval forms in fluid aspirated from lung. Clin Infect Dis 2010;51:804-805, 865-866.

One month after being treated for "pneumonia," an 8-year-old boy from Botswana presented with a one-day history of fever, cough, and chest pain. He was tachypneic and had radiographic evidence of an encapsulated structure in the left chest containing an air-fluid level. A liver cyst was also noted on computed tomographic (CT) imaging. Three days later, he developed more acute respiratory distress with a pneumothorax. During thoracostomy, pleural thickening and a bronchopleural fistulae were identified. An hydatid cyst was removed via lobectomy. Typical Echinococcus granulosus structures were identified histologically. Post-operatively, he was treated with albendazole for three months.

A 7-year-old boy in India who was reportedly "inseparable from his pet dog" sought medical care with a two-week history of respiratory symptoms. A chest radiograph showed an effusion. Fluid was drained percutaneously, and a cyst was aspirated transthoracically. Active, motile parasites were identified in the cyst fluid; characteristic "mouth parts" of Echinococcus granulosus were seen under magnification. The boy was treated with albendazole for six weeks.

Commentary

With widespread international travel, medical personnel who care for immigrants and returned travelers can expect to see parasitic infections they might otherwise have relegated to distant memories of medical school parasitology courses. As demonstrated by these two recently reported children, hydatid disease is still a real clinical problem to reckon with.

Echinococcus granulosus1 is a global cestode tapeworm that usually lives in sheep (as the intermediate host of parasite larvae) and dogs (as the definitive host of adult parasites). Human infection most often occurs following ingestion of eggs from the feces of infected dogs, sometimes from close contact with contaminated muzzles and paws. The "hatched" parasites then cross the human intestinal lumen to gain access to the portal circulation and, eventually, the liver and/or lungs. In about 10% of infected children, other tissues are also involved. Multiple cysts are observed in about one-fourth of infected children. Cysts are often asymptomatic, but they can cause upper abdominal pain with nausea and vomiting. Rupture of a cyst can result in fever, abdominal pain, and allergic symptoms as serious as anaphylaxis. Pulmonary findings can also result from erosion or fistulization of a cyst into the airway. The diagnosis is based largely on historical findings associated with radiographic evidence of typical cysts. The disease may be staged by classification of the cyst. Serologic tests can be useful in confirming a diagnosis. Cyst rupture, even if associated with medical intervention, has provoked worsened symptoms, so the previous mainstay of treatment was surgical excision of an unruptured cyst. More recently, however, improved results have been seen using chemotherapy, such as albendazole. Then, depending on the number and nature of the cysts, treatment is instituted combining percutaneous aspiration, injection of a parasiticidal agent, and re-aspiration. Widespread eradication efforts involve alterations in sheep-slaughtering practices and treatment of dogs but have only been successful in Iceland, Tasmania, and New Zealand.

Beyond echinococcosis, other parasitic worms can also cause pulmonary findings in children.2 Hookworm, picked up by skin contact with fecally contaminated dirt or grasses, and Ascariasis, transmitted by the fecal-oral route, both have larval stages that pass through human lungs. Fever, cough, and wheezing can result, and eosinophilia often is found during the passage of larvae through the pulmonary system. Both mebendazole (100 mg by mouth twice daily for three days, same dose for children as for adults) and albendazole are effective for treatment. Pulmonary strongyloidiasis, transmitted by skin contact with contaminated soil but sometimes perpetuated by auto-reinfection, is occasionally complicated by bacterial superinfection. This occurs when bacteria carried by larvae penetrate the intestinal lumen and enter the human vascular system — a potentially fatal event. Severe disease is most common in immunocompromised patients, such as those receiving chemotherapy. Treatment with ivermectin or albendazole is helpful.

Young schistosomal parasites that develop in the human after skin contact with contaminated fresh water will also pass through the lungs en route to the establishment of adult worm infections in the vascular system. Symptoms can include fever, cough, respiratory distress, and eosinophilia one to two months following the initial infection. Praziquantel provides effective treatment of adult worms and can also help with early pulmonary infections. Paragonimiasis is contracted by eating raw, parasite-infected freshwater crabs and crayfish. It is associated with fever, cough, and even hemoptysis. Praziquantel is the treatment of choice.

Certainly, parents would prefer that their traveling children not develop infection with pulmonary parasites. Prevention of all these different infections, however, requires blocking skin contact with soil and grasses through the use of shoes and clothing, avoiding contact with fresh water in areas where schistosomes live, and the "usual" remembering to apply good hand hygiene, eating only well-cooked foods, and drinking only pure or treated beverages. The elimination of all contact with parasites can be very difficult, and the development of respiratory symptoms following international travel should prompt health care providers to consider the possibility of parasitic lung infections. Of course, tuberculosis should always be part of the differential diagnosis.

References

  1. White AC, Fischer PR, Summer AP. Cestodes. In: Feigin RD, Cherry JD, Demmler-Harrison GJ, et al, eds. Textbook of Pediatric Infectious Diseases, 6th edition, Saunders Elsevier, Philadelphia, 2009, pages 2996-3015.
  2. Vijayan VK, Kilani T. Emerging and established parasitic lung infestations. Infect Dis Clin N Am 2010;24:579-602.