the freshwater
which liver
2
snails
The shell of the freshwater
snail in which stomach fluke
multiply.
cycle
600
1
on
1
The shell of the freshwater
snail in which liver fluke
multiply.
er
Life cycle of flukes in the environment
LIFE
CYCLE snails
OF FLUKES
IN THE
- TRANSMISSION
Freshwater
are active during
late ENVIRONMENT
spring, summer and early
autumn.
Stomach fluke
pa
th
o a
sh
d b
se
nsi
Liver fluke
Volume 22 • Issue 02 • 2018
This is the stage that is infective for livestock and in this form, the flukes can survive for a few months.
LIVER FLUKE - DETAILED
UNDERSTANDING OF THE DISEASE PROCESS
THAT TAKES PLACE IN THE ANIMAL
Safer period to graze wetlands.
4
1. Start of infection
The signs of disease will depend on the number of infective
worms (high, medium or low) taken in by the animal. The
signs that will be seen with a medium to high infection are
described here.
Danger period to graze wetlands on infected farms.
2. Week 1-8
Animals show rapid weight loss, weakness, signs of
blood loss and even sudden death if the infection rate is
extremely high.
3. >12 Weeks
Affected sheep can fall behind when herded or develop
bottle jaw which is a sign of slow blood loss. Continued
weight loss especially during the period when the grazing
is poor.
4. Examination of dead sheep
When a veterinarian cuts the dead animal open he will
look for signs of liver damage (thickened gall tubes)and
flukes in the gall tubes
Development of liver fluke inside Cattle
When the animals graze in wet areas they take the
immature worms which are attached to plants.
In side the animal, these immature flukes
penetrate through the wall of the small intestine,
migrate to the liver and penetrate the liver.
The immature flukes will then start to eat liver
tissue, forming small tunnels in the process.
Immature flukes feed on the liver for the next
6-8 weeks while they are growing which causes
severe damage to the liver. Liver damage depends
on the number of immature flukes feeding on the
liver tissue.By 8 weeks they become adult flukes
which will now enter the small bile ducts (tubes)
and migrate to the larger bile ducts. These adult
flukes attach to the wall of the bile ducts and feed
by drinking blood. After a month each adult starts
2
3
plant and form a protective capsule around it.
fluke
8
1
rainwater into areas with standing
water. Freshwater snails become
infected by this stage of the flukes.
These flukes will now multiply
inside the freshwater snail.
produce eggs that are
excreted with the dung.
Eggs in the dung hatch
with an increase in
temperature.
1. The
shell of the freshwater Spring
snail in which liver fluke multiply Summer and autumn
Winter
Adult
liver of
and
stomach
this stage
of the stomach
parasite it fluke multiply
During high rainfall, the flukes that have multiplied inside the freshwater snails are released into the water again.
2. The
shell
the
freshwater At
snail
in which
flukes
inside livestock
is washed
out of the dung by
Images
supplied
by Karen Grobler
at Afrivet
At this stage, the flukes can swim. The small flukes swim until they reach a plant that grows in the water. They will attach to the
to produce eggs (20 000 per day) which go with
the bile into the intestine and out with the dung.
The thin walls of the bile ducts now become
thickened and white and the whole liver can
become hard (fibrotic) due to the bodies reaction
to this infection.
To confirm infection in the live animal, dung must
be collected and sent to the veterinarian for tests
to determine if there is a liver fluke infection. The
newest tests can identify the infection early (from
4 weeks after infection), which will be at the time
when the first signs of disease are observed in the
case of a very severe infection
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