Human Paragonimiasis after Eating Raw or Undercooked Crayfish — Missouri, July 2006−September 2010

SL Patrick, PhD; G Turabelidze, MD; H Marx; A Grim, MPH; MA Lane, MD; GJ Weil, MD; TC Bailey, MD; NF Önen, MD; LM Demertzis, MD; PG Tuteur, MD; EV Hayes MD; SZ Davila, MD; SM Folk, MD; RE Mitchem, DO; E Kammerer, MD; LP Fannon Jr; JL Jones, MD; PP Wilkins, PhD; YC Lo, MD


Morbidity and Mortality Weekly Report. 2010;59(48):1573-1576. 

In This Article

Abstract and Introduction


Paragonimiasis is a parasitic disease caused by Paragonimus trematodes, commonly known as lung flukes. Humans become infected by eating raw or undercooked crayfish (also known as crawfish and crawdads) or freshwater crabs that harbor the parasites. Paragonimiasis most frequently involves the lungs, but can affect other organs, including the brain and skin. In North America, Paragonimus kellicotti causes infections among dogs, cats, and wild carnivores, but rarely infects humans.[1] Paragonimiasis is not a nationally notifiable condition. In September 2009, physicians from the Washington University School of Medicine (WUSM) in St. Louis published details of three paragonimiasis cases diagnosed since July 2006 in persons who had eaten raw crayfish from rivers in Missouri,[2] prompting the Missouri Department of Health and Senior Services (MDHSS), CDC, and WUSM to collaborate in paragonimiasis surveillance and prevention. During September 2009–September 2010, six additional cases were diagnosed in Missouri. These nine patients, aged 10−32 years, had fever, cough, pleural effusion, and eosinophilia. All had eaten raw or undercooked crayfish from rivers in Missouri while on canoeing or camping trips within 4 months of illness onset. Health-care providers should consider paragonimiasis when examining patients with unexplained fever, cough, eosinophilia, and pleural effusion or other chest radiographic abnormalities and should ask those patients whether they have eaten raw or undercooked crayfish.

The WUSM article[2] and reports of two paragonimiasis cases in October 2009 prompted MDHSS, the Missouri Department of Natural Resources, and the Missouri Division of Tourism to distribute posters warning against eating raw or undercooked crayfish to campers and canoe outfitters in November 2009. After the sixth case was reported in April 2010, MDHSS issued a health advisory on April 30 to enhance health-care provider awareness about paragonimiasis and to request voluntary reporting of cases. MDHSS developed an investigation form and revised the Missouri Health Surveillance Information System for reporting of paragonimiasis. In May, WUSM issued a press release to publicize the series of six cases, resulting in an additional patient (patient 7) seeking evaluation in June, 10 months after illness onset and after having undergone multiple diagnostic tests and failed treatments. In September, a medical center in northwest Missouri reported the other two cases.

Clinical information and exposure histories were collected through medical record review and interviews of patients and the parents of a patient by attending physicians. Sputum, stool, pleural effusion, and lung biopsies, if available, were examined microscopically for Paragonimus parasites or eggs. Serum samples were tested for Paragonimus antibodies by enzyme-linked immunosorbent assay (ELISA) at a commercial laboratory or by immunoblot assay at CDC. Seven patients lived in Missouri and two in Illinois (Table). All nine patients had eaten raw or undercooked crayfish directly taken from rivers in Missouri (i.e., Current, Jacks Fork, Huzzah, Little Niangua, and Meramec) while canoeing or camping within the months of May–August during 2006–2010. Among the eight adults, seven had eaten raw crayfish during group canoe trips, and the other had eaten undercooked crayfish while camping. Seven adults had eaten raw or undercooked crayfish after alcohol consumption; two had eaten raw crayfish on dares. The child had eaten a small raw crayfish while camping to demonstrate outdoor survival skills to other children.

Illness onset ranged from 2−16 weeks after crayfish ingestion. Common signs and symptoms were fever (100%), cough (100%), weight loss (56%), malaise (56%), chest pain (44%), dyspnea (44%), myalgia (44%), and night sweats (44%). Cough was not among the earliest indicators for patients 1, 4, and 7. Patient 1 experienced fever and headache 3 weeks before the onset of mild nonproductive cough. Two patients (patients 4 and 7) experienced upper-abdominal pain 6−8 weeks after crayfish ingestion. Patient 4 underwent emergency cholecystectomy for suspected acute cholecystitis, but his resected gall bladder was normal. Patient 7 experienced acute chest pain 2 weeks after experiencing abdominal pain. In addition, patient 8 experienced bilateral spontaneous pneumothoraces 3 weeks after the onset of fever, dyspnea, and nonproductive cough. These clinical manifestations likely were caused by P. kellicotti migration through the diaphragm into the pleural space and lungs.

During routine clinical care, all patients received a presumptive diagnosis of paragonimiasis 3−45 weeks after illness onset. All had eosinophilia (range: 850−3,900 eosinophils/mm3; eosinophil percentage: 7%−40%) and pleural effusion. Pleural effusions were analyzed for six patients. Five patients had eosinophilic pleural effusion, defined as a pleural effusion with ≥10% eosinophils (eosinophil percentage: 44%−90%; normal: ≤3%). Other chest radiologic abnormalities included pulmonary nodules (four patients), pericardial effusion (three patients), pulmonary infiltrates (three patients), and pneumothorax (one patient). Extrapulmonary complications included migratory skin nodules (four patients), cardiac tamponade (one patient), and cerebral lesions (one patient) associated with blurred vision.

P. kellicotti eggs were identified in sputum or bronchoalveolar lavage fluid from two patients 40–45 weeks after illness onset. Paragonimus antibodies were positive by ELISA or immunoblot for seven patients (Table). Among seven patients (patients 1 and 4−9) whose serum samples were tested for Paragonimus antibodies by immunoblot, three (patients 1, 4, and 5) tested negative in two consecutive serum samples collected ≥1 month apart. An acute serum from patient 4 was tested by ELISA; the result was positive. Patients 1 and 5 were diagnosed on the basis of their clinical histories and findings and response to therapy.

All patients were treated with 75 mg praziquantel per kilogram of body weight in 3 divided doses for 2–3 days. Their symptoms promptly improved. All symptoms, eosinophilia, and radiographic abnormalities resolved within 1−3 months of treatment.