Fasciola hepatica - Laboratory Diagnosis, Transmission, Treatment, Prevention, Control

Transmission of Fasciola hepatica

The transmission of Fasciola hepatica occurs via the following routes:

• drinking water contaminated with metacercariae

• consumption of plants harbouring metacercariae – including watercress, lettuce, and aquatic plants generally eaten raw

• eating raw or undercooked sheep, cattle liver as seen in Halsonum and Marrerra syndrome

Laboratory diagnosis of Fasciola hepatica

The laboratory diagnosis of Fasciola hepatica starts with the collection of samples, followed by microscopy, serodiagnosis, and imaging methods.

Sample

Samples collected include:

• stool

• biopsy tissues (liver, skin, lung, heart, brain, eye, intestine)

• blood (serum)

Microscopy

• microscopic diagnosis of fascioliasis is commonly done by demonstration of Fasciola hepatica eggs

• useful to determine chronic fascioliasis but not acute fascioliasis

• in acute cases, eggs are scanty and intermittent

• concentrations are done by sedimentation in 0.5% glycerinated saline, formalin-ether concentration method

• cannot distinguish between Fasciola hepatica and Fasciola buski eggs

Stool antigen detection

• Enzyme-linked immunosorbent assay (ELISA) can be done in stool samples to detect Fasciola corpo-antigen for chronic infection

Serodiagnosis

Serodiagnostic methods can be done for early detection of liver fluke infection as these tests are able to demonstrate infection in the serum within 2- 4 weeks of infection – which is 4 to 8 weeks before eggs are released in the stool.

• serodiagnosis for Fasciola hepatica can detect the infection early – during the pre-patent period which prevents liver damage due to chronic fascioliasis

• useful to detect acute fascioliasis and ectopic fascioliasis as eggs are not passed in the faeces in such conditions

• prevents pseudofascioliasis in which eggs are seen in the stool but is not due to active infection but due to ingestion of raw sheep or cattle liver containing Fasciola hepatica eggs

Numerous methods used for serodiagnosis include:

• immunoelectrophoresis

• indirect haemagglutination

• indirect immunofluorescence

• Western blot - 100% specificity when 12kDa, 17kDa, and 63kDa Fasciola hepatica antigen are used

• enzyme-linked immunosorbent assay (ELISA) – has 95% sensitivity and

  * uses excretory-secretory antigen of Fasciola hepatica

Intradermal Skin Test

The intradermal skin test involves the administration of fascioline into the intradermal layer of the patient’s skin. Fascioline is an extract of adult Fasciola, with a nitrogen content of 0.3ng/ml.

Molecular test

Important molecular tests of Fasciola hepatica diagnosis include:

• DNA probes

• PCR

Fasciola hepatica and Fasciola gigantica can be differentiated by the use of protein banding patterns after isoelectric focusing.

Imaging Methods

• Ultrasonogram (USG) shows hypoechoic lesions in the liver made by migrating larvae, as well as adult Fasciola hepatica, flukes in the gallbladder or the bile duct

• CT-scan

• MRI

Treatment of Fasciola hepatica infection

Drug of choice for the treatment of Fasciola hepatica infection is bithionol and Praziquantel.

Prevention, Control of Fasciola hepatica

The control and prevention of Fasciola hepatica can be obtained by following steps:

• avoid consumption of raw/undercooked sheep/cattle liver

• thorough cleaning and decontamination of salad vegetables such as watercress and other water-grown greens

• proper filtration and/or boiling of drinking water

• immediate treatment of infections in sheep, cattle, and people

• use of molluscicides to control snails

• reduce contamination of water sources by animal faeces