Ascaris lumbricoides is an intestinal nematode (roundworm); it is one of the most common helminthic human infections worldwide . Issues related to pulmonary infection are reviewed here. The epidemiology, clinical manifestations, and diagnosis of ascariasis are discussed separately. (See "Ascariasis".)
The life cycle of ascariasis is summarized separately (figure 1). In general, within four days following oral ingestion of eggs, they hatch in the small intestine and release larvae which migrate hematogenously to the lungs. Within the alveoli of the lungs, the larvae mature over a period of approximately 10 days, then ascend the bronchial tree and are swallowed.
Respiratory manifestations occur primarily in the first stage of infection; they rarely complicate the intestinal phase.
The syndrome of eosinophilic pneumonitis among patients originally described by Loeffler was attributed to Ascaris infection retrospectively; ascariasis remains the most common cause of Loeffler's syndrome worldwide [2,3]. Transient respiratory symptoms can occur during migration of Ascaris larvae through the lungs; this occurs one to two weeks following ingestion of eggs. The severity of symptoms correlates to some degree with larval burden, although pulmonary symptoms are less common in regions with continuous transmission of A. lumbricoides [4-8].
Symptoms include dry cough and burning substernal discomfort. Some patients experience dyspnea and blood-tinged sputum. Urticaria occurs in about 15 percent of cases . Fever occurs in many patients though rarely exceeds 38.3ºC (101ºF). Over half of patients have crackles and wheezing, in the absence of consolidation. Hepatomegaly may develop. Lymphadenopathy is generally not observed. Symptoms generally subside within 5 to 10 days. Ascaris pneumonia is self-limited and only very rarely fatal.