Paragonimiasis is a foodborne tissue-invasive parasitic infection caused by Paragonimus westermani. The infection is closely related to eating habits, and in humans it results from eating freshwater crayfish or crabs, secondary intermediate hosts or the flesh of wild boar, the paratenic host contaminated with the metacercariae of paragonimus.1 Although paragonimiasis is primarily a pulmonary disease, ectopic infection can occur in unexpected sites because of the complexity of the migration route of Paragonimus in the definitive hosts.2 Cutaneous or cerebral paragonimiasis are the known forms of ectopic infestation of paragonimiasis, but hepatic paragonimiasis is rare.3 Furthermore, consecutive and multiple ectopic organ involvement in paragonimiasis is very rare, especially in the liver and colon. Here, we report a case of consecutive extrapulmonary paragonimiasis involving the liver and colon.
A 44-year-old woman was transferred to Keimyung University Dongsan Hospital, Daegu, Korea in January 2010 due to skin rash and itching sensation. While she was suffering from the above symptoms, her husband had been diagnosed with an eosinophilic liver abscess, so she visited her local hospital to work up her symptoms. Subsequently, peripheral blood eosinophilia, positive skin test for dog allergen and a hepatic abscess on abdominal computed tomography (CT) were incidentally found. On admission to our hospital she was afebrile and a physical examination yielded no specific findings. Routine blood test revealed a white blood cell count of 7.65 × 109/L (eosinophil 20.9%, normal range <7%), hemoglobin (Hb) 96 g/L, platelet count 209 × 109/L. Serum biochemistry, immunoglobulin (IgE) level, electrolytes and urine analysis revealed no abnormal findings, and stool examination for various parasitic eggs was also negative. The result of chest X-ray was unremarkable. An abdominal dynamic CT scan showed irregular and hypoattenuated lesions in the posteroinferior segment of the right lobe of liver (Fig. 1). A transabdominal needle biopsy was performed under CT guidance for a histological confirmation of liver lesions. The specimens were diagnosed as chronic granulomatous inflammation with eosinophil infiltration (Fig. 2). Based on the skin test and laboratory findings, we considered that she might have a parasite infection transmitted from dogs, she was treated with praziquantel (75 mg/kg/d for one day) and albendazole (400 mg twice daily for 3 days). Three months after medication, a follow-up CT scan showed that the hepatic lesion slightly decreased in size and consolidation (Fig. 3). The peripheral blood eosinophil decreased to 11.3%. However, after 5 months, new lesions were detected at the lateral segment of the liver (Fig. 4a) and transverse colon (Fig. 4b). A colonoscopic finding showed a 10-cm long, diffuse encircling wall thickness at mid-transverse colon. Biopsy specimen showed chronic colitis with abnormally increased eosinophil infiltration (Fig. 5). Furthermore, peripheral blood eosinophilia of 36.7% persisted. As the clinical findings were indicative of an unusual parasitic infection, an antibody test by enzyme-linked immunosorbent assay (ELISA) was performed and the results indicated the presence of a Paragonimus westermani-specific antibody. Although there was no history of freshwater crayfish or crab intake, she was diagnosed with ectopic paragonimiasis and treated with praziquantel (75 mg/kg/d for one day). A repeated CT scan a month later showed that the hepatic lesions had greatly decreased in size (Fig. 6a) and the transverse colonic lesions were resolved (Fig. 6b). At 10 months follow-up after the initial treatment, the liver abscess had nearly complete improvement and peripheral blood eosinophilia was within normal range.
Infection with Paragonimus is common in limited areas of Asia such as China, Korea, Japan, the Philippines, and some areas of Latin America and Africa (especially in Nigeria).4 However, nowadays, because of the increased numbers of immigrants, overseas travelers, and worldwide food trading, human paragonimiasis has been detected in almost every location of the world.5
The incidence of paragonimiasis has recently decreased, due to a successful eradication program and changes in dietary habits in Korea, where the disease is known to be endemic. The incidence of paragonimiasis during the 1990s decreased to approximately 1% of that of the early 1970s in Korea. However, there are still high chances of infection because traditional soybean-sauce soaked freshwater crab (Kejang) is a favorite local food and at least 10% of freshwater crabs sold in local markets are contaminated with the metacercariae of Paragonimus westermani.6
If people ingest food stuffs contaminated with metacercariae, the larvae penetrate the walls of the intestine and move to the liver and spleen, and through the free pleural space into the lungs. They can live for up to 5 years or more.7 Because of the complexity of the migration route in the final host, this parasite often causes an ectopic infestation at various sites, such as brain, mesentery, genital tract, pleura, peritoneum, spleen and liver.8
Diagnosis is established by the detection of the characteristic ova in the stool or sputum.9 However, eggs may not be detected until 2 to 3 months after exposure in acute disease or ectopic infection.10 The inadequacies of sputum or stool examination for the diagnosis of paragonimiasis are well recognized, so highly sensitive and versatile serodiagnostic tests based on ELISA are now used as the predominant assays in biomedical research. Serological testing for anti-paragonimus IgG is very useful and it has a sensitivity of 100% and a specificity of 91.3–100%.11 In this case, we found no eggs in the stool. An ELISA for the paragonimiasis-specific IgG antibody, however, showed a positive result and allowed us to confirm the patient's paragonimiasis.
Previous studies reported that peripheral blood eosinophilia was found in more than 80% of paragonimiasis patients.12 Eosinophilia is found only the parasites are alive and migration,4 indicating the acute phase response of the host.13 In this case, the patient showed peripheral blood eosinophilia. Accordingly, she might have been in an acute infectious state with paragnimiasis at her first admission. After five months of the first treatment, the patient showed persistent high eosinophils level. We therefore thought that the parasites might still be alive and were migrating to the transverse colon.
Paragonimiasis needs specific chemotherapy, which results in an immediate improvement.4 An immediate and correct diagnosis is therefore very important. If a liver abscess is detected in patients live in or have traveled to an endemic paragonimiasis area, we should always consider paragonimiasis in the differential diagnosis. Praziquantel (75 mg/kg/d given in three doses for 2 days) is the therapeutic agent of choice for paragonimiasis.14 Studies have shown a 71–75% cure rate after one day, an 86–100% cure rate after 2 days and a complete cure after 3 days with this dosage.15
Although she was misdiagnosed at the first admission, our patient had taken praziquantel and follow-up CT scan showed improvement of the hepatic lesions. However, new lesions subsequently developed at the transverse colon and the lateral segment of the liver. We think that was caused by incomplete eradication of the parasite at the first treatment. She was treated repeatedly with praziquantel and clinically improved. This case report has served to remind physicians that paragonimiasis must always be considered in the differential diagnosis of liver abscess with elevation of peripheral blood eosinophils, although the global incidence of paragonimiasis has decreased.