Trematode infections of liver 
Fasciola, Clonorchis, Opisthorchis are together called as 
liver flukes. Fasciola infect liver and bile duct, whereas the 
others infect only the bile duct. 
Life Cycle
Life cycle of liver flukes is similar to as described for other 
trematodes, except schistosomes (Chapter 46, Figure 46.12).
 Morphology: Similar to other trematodes, they have 
adult worm (leaf-like), operculated eggs, and larvae (in 
five stages) 
 Hosts: Liver flukes have three hosts
 Definitive host: Humans are the definitive host. 
Other animals can also act as definitive host such as—
sheep for F. hepatica (also called as sheep liver fluke) 
and dogs and cats for Clonorchis and Opisthorchis
 Intermediate hosts: Snails are the first intermediate 
host, whereas the second intermediate host is aquatic 
plant (for Fasciola) and cray fish (for Clonorchis, and 
Opisthorchis)
 Transmission: Man gets infection by ingestion of second 
intermediate host carrying metacercaria larvae (infective form)
 The larvae excyst and penetrate through the intestinal 
wall to migrate to their habitat (liver or bile duct), where 
they develop into adult worms
 Adult worms undergo fertilization to produce eggs. Eggs 
are passed from the bile duct or liver to intestine and 
excreted in feces (diagnostic form).
Fascioliasis 
Fascioliasis (caused by Fasciola hepatica), although 
reported worldwide is particularly endemic in sheepraising countries such as Peru, Bolivia, and Chile. In India, 
it is extremely rare. 
Clinical Features 
 Liver: Migration of metacercaria larvae into liver 
causes fever, right upper quadrant pain, hepatomegaly 
and eosinophilia. Liver parenchyma is inflamed with 
formation of multiple subcapsular abscesses (called as 
liver rot) 
 Bile duct: The adult worm can cause obstruction of the 
bile duct and dilatation of the biliary tract and biliary 
cirrhosis. It does not cause malignancies
 Halzoun or Marrara syndrome: In endemic areas (e.g. 
Lebanon or Sudan) where uncooked goat and sheep 
livers may be eaten, the adult worms may attach to 
the pharyngeal wall; causing severe pharyngitis and 
laryngeal edema. 
Laboratory Diagnosis 
 Stool microscopy reveals characteristicoperculated eggs, 
measuring130–150 μm × 63–90 μm in size (Fig. 49.7A). 
Concentration techniques (by sedimentation methods) 
can be followed to increase the sensitivity. Floatation 
methods are not useful. Egg of F. hepatica is similar to 
that of Fasciolopsis buski
 Antibody detection: ELISA or western blot are available 
to detect serum antibodies against excretion secretion 
antigen. It helps in the early diagnosis before the eggs 
are detected in stool, useful for the seroepidemiological 
study and to monitor the response to treatment Molecular methods: Various PCR-based methods are 
available to detect F. hepatica specific genes in stool 
specimens
 Imaging methods like ultrasound, CT scan or MRI can 
be employed to detect the lesions in the liver.
Fasciola gigantica
F. gigantica is closely related to F. hepatica. It is a common 
parasite of herbivores like cattle; human infection is rare. 
Eggs of F. gigantica are morphologically similar to that of 
F. hepatica and but larger in size. Rest of life cycle, clinical 
feature, laboratory diagnosis and treatment are similar to 
that of F. gigantica.
Clonorchiasis and Opisthorchiasis
Clonorchis sinensis (called as Chinese or oriental liver 
fluke) is found primarily in Eastern Asia like China, Korea, 
Japan and Malaysia. 
Opisthorchis viverrini has been reported from Southeast 
Asia, mainly from Laos, Thailand and Cambodia. In India, 
they are not reported yet. Opisthorchis felineus (cat liver 
fluke) is another species, that is limited to Central and 
Eastern Europe, Russia and Kazakhstan.
Clinical Features 
In chronic infection with heavy worm burden, they cause 
mechanical obstruction of the bile duct and irritation due to 
toxin released by the flukes leads to cholangitis, dilatation of 
the bile duct, marked ductal epithelial hyperplasia, and fibrosis leading to cholangiocarcinoma (bile duct carcinoma). 
 They inhibit tumor suppressor genes (p53) and release 
of cytokines such as IL-6 and TNF-α (factors associated 
with carcinogenesis)
 In addition, O. viverrini can also cause hepatocellular 
carcinoma; reported mainly from the Northeastern 
Thailand.
Laboratory Diagnosis 
 Stool microscopy: Demonstration of the characteristic 
flask-shaped eggs (measures 28–35 μm × 12–19 μm) in 
the stool establishes the diagnosis. Eggs of Clonorchis
and Opisthorchis are morphologically indistinguishable 
(Fig. 49.7B). 
 Microscopy of the duodenal aspirate is more sensitive 
than stool microscopy. Entero-test can be done to take 
duodenal contents (similar to that is done for Giardia) 
 Formalin ether concentration should be done when 
egg burden is low. 
 Antibody detection: ELISA using recombinant 
propeptide of cathepsin L proteinase is available for 
detection of specific IgG4 antibodies against C. sinensis. 
It is used to evaluate the level of infection and for 
monitoring the treatment response 
 Antigen detection: ELISA is also available for the 
detection of circulating antigen in the serum. Detection 
of antigen is more useful as it indicates current infection 
 A multiplex PCR has been developed to detect Clonorchis
and Opisthorchis simultaneously. It is rapid with high 
sensitivity and specificity.
 Triclabendazole (10 mg/kg once) is the drug of choice for 
fascioliasis 
 Praziquantel (25 mg/kg, three doses in 1 day) is the drug of 
choice for clonorchiasis and opisthorchiasis.
T Reatment Liver fluke infections
Prevention (Liver Fluke) 
Common preventive measures include sanitary disposal of 
sewage, and control of snail hosts
 Fascioliasis can be prevented by avoidance of 
consumption of alfalfa juice, raw water plants and 
cleaning them before use 
 Clonorchiasis and opisthorchiasis can be prevented by 
avoidance of eating raw or undercooked fresh water fish.
Hepatosplenic Schistosomiasis
Lodging of Schistosoma mansoni and S. japonicum eggs 
in the liver can lead to granuloma formation and fibrosis 
(called as Symmers pipestem fibrosis).
 Fibrosis impedes the portal blood flow leading to portal 
hypertension, hepatomegaly, splenomegaly (enlarged 
and hard) and gastric varices
 S. mansoni is increasingly associated with hepatitis 
C virus; particularly in Egypt and accelerates the 
occurrence of chronic hepatitis and cirrhosis in these 
patients
 Hepatitis B virus infection has been associated with S. 
japonicum. In consice form for studying for exams