Image Source: http://www.dpd.cdc.gov/dpdx/images/ParasiteImages/A-F/Fascioliasis/Fasciola_LifeCycle.gif
Eggs have an incubation
period of 14-17 days and hatch in water to
release miracidium. The miracidium infects
lymnaeid snail during its larval
multiplication giving rise to cercariae.
This is an important process with one
miracidium giving rise to as many as 600
cercaria. The cercaria then develops into a
metacercaria which is enveloped in a cyst
and attaches to aquatic vegetation. Once it
is ingested by a definitive host the
metacercardia excyst and into the intestine.
The liver fluke burrow into the liver and
travel into the bile ducts where the adult
fluke develops. The eggs are passed in feces
contaminating the water and vegetation.
Symptoms
Most of the symptoms
are caused by biliary obstruction. In humans
most of the symptoms reported are high
fever, diarrhea, chills, bile inflammation,
liver enlargement, and Jaundice.
Pharyngeal form of
fascioliasis can be seen among people who
eat raw animal liver mostly in the Middle
East with characteristic symptoms of
bleeding and pain of the pharynx.
Pathogenesis
Mechanical obstruction
caused by fluke results in inflammation of
the bile duct. The parasite also secretes
toxic chemicals that lead to irritation of
liver tissue in sheep. Bacteria infection
may also follow leading to more
inflammation. Snails infected by the
parasite also are enlarged supporting
further parasitic growth.
Diagnosis
Fasciola hepatica eggs
can be found in a stool sample or bilary
aspirate. Ultrasonography can be used to
observe adult worms in the liver. The damage
caused by the parasite in the liver can be
visualized by using endoscopy. Enzyme linked
immunosorbent assay (ELISA) can be a more
accurate diagnostic test to test for antigen
of Fasciola hepatica.
Treatment
Bithionol-
Orally administered
with a dose of 30-50mg/kg every other day
for total dose of 10 to 15.
Side effects- skin
reaction, vomiting, diarrhea, abdominal
pain.
Praziquantel-
Daily dose of 25mg/kg
(3X) for a total dose of 5-7 with minimal
success in elimination of the parasite.
Effective in lowering minimizing the level
of infection.
Triclabendazole-
A dose of 10mg/kg body
weight per day (2X). Perfect cure rate with
a single dose is reported with minimal side
effect. However, this drug has not been
approved for human use in the United States.
|
