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A 35 year old female presented with complaints of fever and malaise. She had no medical history. There were no respiratory or urinary tract symptoms. She had visited Northern Italy 3 weeks before, but not the tropics. Her father had similar complaints.
On physical examination no fever was present and no other abnormalities were detected. Laboratory results showed mildly elevated liver enzymes, CRP 39 mg/L and leukocyte count 11.2 x 109/L, 30 percent eosinophiles. Chest X-ray and abdominal ultrasound showed no liver abscess or other abnormalities. Because of the eosinophilia parasitological examination of the stool was performed. On microscopy one liver fluke egg was detected. PCR on the stools confirmed an Opisthorchis felineus infection.
Opisthorchis felineus is part of the family Opisthorchidae, Class Trematodes (flukes). Fluke-infection is a common food borne parasitic zoonose in Southeast Asia (Clonorchis sinensis, Opisthorchus viverrini and Fasciola spp) and in Eastern Europe, mainly Russia and Siberia. Worldwide the number of human infections with O. felineus has been estimated to be 1.2 million. Infection in Western Europe is extremely rare. The trematode lives in the biliary duct of mammals where it reproduces. The eggs are excreted with the faeces. Water snails eat these eggs that develop into miracidia and free swimming cercariae. These cercariae invade freshwater fish such as the tench (member of the carp family)and develop into the infectious stage of metacercaria. By eating raw fish containing metacercaria mammals, including humans, can be infected. The incubation period is 2-4 weeks. Acute symptoms are abdominal pain, fever and malaise. Chronic complications include liver abscess and biliary duct carcinoma.
The diagnosis is made by microscopic detection of eggs in the faeces. It is impossible to differentiate microscopically between the liver flukes Opisthorchis and Clonorchis , hence specific PCR testing is needed. The diagnosis can be confirmed by a positive antibody test.
Our patient had eaten raw fish in a restaurant in Italy, carpaccio of tench. Public health services in Italy report that a large percentage of tench in central Italian lakes are infected by O. felineus. Fish can be decontaminated by heating to 70°C or freezing below -28°C. Eggs of the parasite have been found in the excrements of stray cats around the lakes. Of the 52 people who had consumed raw fish in the restaurant concerned, 45 presented with symptoms. Eight of them were admitted to the local hospital. One patient developed a liver abscess. All patients were treated with praziquantel 75mg/kg/dd. Our patient made a full recovery.
Doctors, patients and caterers should be aware that changing eating habits, e.g. consumption of raw fish in Europe, can lead to an incline of parasitic infections.