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Pulmonary manifestations of ascariasis

Peter F Weller, MD, FACP
Karin Leder, MBBS, FRACP, PhD, MPH, DTMH
Section Editor
Edward T Ryan, MD, DTMH
Deputy Editor
Elinor L Baron, MD, DTMH


Three types of helminths have life cycles in which infecting larvae reach the lungs via the bloodstream: Ascaris, hookworm, and Strongyloides [1]. Two Ascaris species may elicit pulmonary symptoms in humans: Ascaris lumbricoides and Ascaris suum; these species are genetically very closely related and may be a single species [2-5].

The pulmonary manifestations of Ascaris infection are reviewed here. The epidemiology, clinical manifestations, and diagnosis of ascariasis are discussed separately, as are general issues related to pulmonary eosinophilia. (See "Ascariasis" and "Causes of pulmonary eosinophilia".)


A. lumbricoides infects an estimated 1.2 billion people worldwide [6]. Issues related to epidemiology of Ascaris infection are discussed separately. (See "Ascariasis", section on 'Epidemiology'.)

Pulmonary ascariasis is rare in highly endemic areas with ongoing exposure [7,8]; it occurs most often in the setting of episodic exposure [9-11]. One study in Colombia (where intestinal Ascaris infection rates range from 25 to 90 percent) noted only four cases of Loeffler syndrome among about 13,000 subjects [7].

There is an increasing recognition that A. suum can cause human infection and symptomatic pulmonary ascariasis. Two reported cases of pulmonary ascariasis initially thought to be due to A. lumbricoides [12] were subsequently reconsidered by the authors to be due to A. suum [12,13]. Cases of pulmonary ascariasis have also been attributed to A. suum infection in Japan, China, Denmark, and the United States [2,14-16].


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Literature review current through: Sep 2015. | This topic last updated: Jun 9, 2015.
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