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Abstract & Commentary
Paragonimiasis Acquired in the United States
By Brian Blackburn, MD, Clinical Assistant Professor of Medicine, Division of Infectious Diseases and Geographic Medicine at Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.
Synopsis: Nine cases of human paragonimiasis occurred after ingestion of crayfish in Missouri over a four-year period. Although rarely documented previously, this appears to represent a focus of autochthonous transmission of this parasite within the United States.
Source: Centers for Disease Control and Prevention (CDC). Human paragonimiasis after eating raw or undercooked crayfish Missouri, July 2006-September 2010. Morb Mortal Wkly Rep. 2010;59:1573-1576.
Shortly after ingestion, patients may develop diarrhea, abdominal pain, fever, chest pain, eosinophilia, and cough. Subsequently, patients may develop eosinophilic pleural effusions, or bronchiectatic and cavitary lung disease with cough and hemoptysis, sometimes mimicking tuberculosis. Less commonly, lesions develop in the brain, skin, or other ectopic sites. Paragonimiasis is most highly endemic to East and Southeast Asia, but transmission occurs in Peru, Ecuador, Nigeria, Cameroon, and other areas.1 While imported cases occasionally occur in the United States, infection acquired within the United States has been described only six times in the literature to date.2 In North America, P. kellicotti causes infections among animals, but rarely humans.1,2
In Missouri, nine people who had developed paragonimiasis between 2006 and 2010 were identified by public-health officials. The patients were aged 10-32 years, and all had eaten raw or undercooked crayfish from rivers in Missouri (during the months of May-August) four months or less before illness onset. Seven (78%) patients were serologically positive for paragonimiasis (two of whom were also positive for P. kellicotti eggs in respiratory secretions), and two (22%) were clinically defined (but seronegative) cases. The patients presented with fever (100%), cough (100%), eosinophilia (100%), weight loss (56%), chest pain (44%), dyspnea (44%), and night sweats (44%). Five had eosinophilic pleural effusions, and other radiologic abnormalities included pulmonary nodules (44%), pulmonary infiltrates (33%), and pneumothorax (11%). Four patients noted migratory skin nodules, one had cardiac tamponade, and one had cerebral lesions. All patients were treated with praziquantel and noted prompt resolution of their symptoms subsequently.
Paragonimiasis is a parasitic infection that predominantly affects the lungs, but through migration of the parasite can also cause skin lesions, pleural effusions, brain lesions, and eosinophilia. Because of the chronic presentation and cavitary lung disease, with cough and weight loss that often results, the disease is commonly confused with tuberculosis; another common misdiagnosis is eosinophilic pneumonia.
Although highly endemic to Asia, and an emerging infection in other parts of the world (such as Latin America and sub-Saharan Africa), paragonimiasis is rare in North America, with transmission described in only a handful of cases to date.2 This report more than doubles the number of cases reported in the United States that appear to have resulted from autochthonous transmission. The public should be educated regarding the risk of raw freshwater crayfish or crab consumption, and clinicians should consider the possibility of this infection in patients with a consistent clinical picture, even if they have not left the United States.
Because clinicians do not usually consider paragonimiasis in the differential diagnosis of patients in the United States, this infection is probably underreported, and likely exists elsewhere in North America. A seventh case in North America (in Montreal, Canada) has also been reported, and numerous others have probably occurred that have not been reported.3
While the patients in this report presumably acquired their infections within the United States (given the compelling exposure histories and timing of illness onset), the authors did not mention the presence or absence of antecedent international travel in these patients. It is, therefore, at least possible that some of them may have traveled outside the United States in the months leading up to presentation, and acquired their infections abroad. Aside from this limitation, this report offers otherwise compelling evidence for a focus of autochthonous transmission of paragonimiasis in Missouri, and raises the possibility of transmission elsewhere in North America. Both the public and physicians in the United States should be better educated about the presence of this parasite, and measures should be undertaken to prevent exposure and to diagnose and treat those already infected.