CLINICAL PRESENTATION IN HUMANS
Ash (1997), Liver Flukes and Malignancy,
Pungpak (1985, 1994), Sun (1999)
Opisthorchiasis results from the liver flukes O.
O. viverrini invading the biliary ducts of the human host as
indicated in the diagram above.
Image from Atlas of Medical Parasitology
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.
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
The incubation period is 2 weeks and worms can live up to 20 years
in their human hosts.
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