CLINICAL PRESENTATION IN HUMANS
Ash (1997), Liver Flukes and Malignancy,
Pungpak (1985, 1994), Sun (1999)

Opisthorchiasis results from the liver flukes O. felineus and
O. viverrini invading the biliary ducts of the human host as indicated in the diagram above.
Image from Atlas of Medical Parasitology website

Symptoms of Opisthorchiasis depend on the quantity of liver flukes in the individual. Clinical cases have discovered fluke quantities that varied from less than 100 to up to 21,000 flukes! Those that have less than 100 flukes usually have no symptoms other than general malaise.


As these flukes invade the liver and biliary passages of humans, severe cases of Opisthorchiasis can present symptoms of diarrhea, abdominal pain, and splenomegaly. Extreme cases can lead to fever, acute pain and enlarged and palpable liver and gallbladder, jaundice, tachycardia, weight loss, and eosinophilia.

 

Pathology of gall bladder infected with Clonorchis.
Similar pathology would be observed with Opisthorchis infection.
Image from Sun, 1999
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Lab tests of cases found high bilirubin, high alkaline phosphatase, elevation of serum transaminase, and low serum albumin. It is also interesting to note that no correlation has been found between the severity of the disease and the fecal liver fluke egg output of the patient. As the flukes block the gallbladder and bile ducts of the human host, eggs may no longer appear in the feces of the host.


Two adult worms (arrow) in the ductal luman.
This liver shows dilation and thickening of the intrahepatic bile
Ducts and are unmistakable features that establish the diagnosis
Of clonorchiasis or opisthorchiasis.
Image from Sun, 1999

CHRONIC INFECTION AND CHOLANGIOCARCINOMAS
Liver Flukes and Malignancy, Pungpak (1985)


Chronic Opisthorchiasis may eventually cause cholangiocarcinomas such as biliary cancer. Though not everyone who has been infected with a liver fluke gets this type of cancer, those who have been infected and treated for Opisthorchiasis acquire cancer at a higher rate than the non-infected population.

A folded adult O. viverrini in the bile duct. Note the many eggs in the uterus.
Image from Sun, 1999

Chronic infection by liver flukes leads to chronic inflammation in the human host. Acute and chronic inflammatory cells are involved in and respond to these conditions and macrophages and eosinophils have been found around the ducts. These cells produce reactive oxygen species and other toxic compounds, such as oxygen radicals that lead to death and regeneration of the bile ducts. This situation could possibly be the mechanism for cholangiocarcinomas associated with Opisthorchiasis.


A section of C. sinensis from the liver shows a large
Sucker on the destroyed epithelium of an intrahepatic
Bile duct. There are many ova in the uterus of the parasite.
Similar pathology would be evident in either O. viverrani or O. felinus.
Image from Sun, 1999


INCUBATION PERIOD
Mehlorn (2001)

The incubation period is 2 weeks and worms can live up to 20 years in their human hosts.

DIAGNOSTIC TESTS
Ash (1997)

First, a history of eating raw, pickled, or poorly cooked fish should be obtained. Diagnosis is made on the detection of eggs in the patient's stool. Fewer than 100 eggs per gram of feces is considered evidence of mild infection and more than 30,000 eggs per gram is considered to indicate severe infection.
If eggs are not detected, examination of duodenal drainage aspiration may detect eggs. This procedure requires hospitalization and is usually indicative of severe infection as the flukes could be blocking ducts to such an extent that eggs cannot be passed on into the stool.
Indirect evidence of Opisthorchiasis in the bile ducts can be obtained by using radiologic techniques. Non-invasive ultrasonography has largely replaced the invasive procedure of obtaining duodenal drainage. Computed tomography can also be used to diagnose Opisthorchiasis.
The enzyme-linked immunosorbent assay (ELISA) remains the most appropriate immunodiagnostic technique for detecting Opisthorchiasis. Interestingly, one study found that the antibody titer to the Opisthorchis antigen was proportional to the changes in the liver detected through ultrasound. This makes ELISA a good predictor of the development of cholangiocarcinoma.

MANAGEMENT & THERAPY
Bogitsh (1998), Mehlorn (2001), Sun (1999)

Praziquantel has been the antihelmintic drug of choice for the past 10 years. A safe and effective dose of 25 mg/kg of body weight, three times a day for two days has been determined. Though this treatment has demonstrated 100% efficacy in eliminating liver flukes, it is not associated with a decreased incidence of cholangiocarcinomas in infected but treated individuals compared to the infected and untreated population.
Because the cultural preference for raw fish is so pervasive in northeast Thailand culture, many individuals continue to eat their traditional cuisine and treat themselves with praziquantel annually as a pseudo prophylaxis for infection. More studies are indicating that irreversible damage is caused to the liver after infection, therefore complete prevention would be better than treatment of infection in order to decrease risk for cholangiocarcinomas.