Parasites - Killingly Public Schools


Parasites - Killingly Public Schools
Horse Strongyles
• Large strongyle worms
occurs commonly among
horses that graze in groups
or on pastures previously
grazed by infected horses
– infected horses pass eggs in
the feces
– Develop into larva which after
two molts become infective
– when L3 gets swallowed by a
grazing horse, it will either
migrate to the small intestine
or the liver depending on the
strongyles species
Horse Strongyles
• Strongylus vulgaris
– Shed infective L3 in small
intestine then into large
intestine causing damage
– Next migrate into blood
vessels causing further
– Extensive damage leads to
blood clots, which can
block the flow of blood to
parts of the intestines
• Necrotic or ruptured
• Colic
• Abdominal pain
Horse Strongyles
• Strongylus edentatus
– Infected L3 migrate to
the large intestines and
then the liver via veins
• larvae develop, grow
larger, and migrate about
the liver for 8 weeks
causing hepatitis
Horse Strongyles
• Strongylus equinus
– Infected L3 travel to the liver, pancreas, and other
parts of the abdomen
– Irritation leads pancreatitis, peritonitis, and
Horse Strongyles
• Small strongyles
– significantly damages a horse’s cecum and colon
by feeding on the superficial lining of the
intestines called the mucosa
– ulcers form and inflammation of the cecum and
– tissues of the intestinal wall will surround the
larvae, protecting them for an extended time
allowing further irritation and damage to the
Horse Strongyles
Horse Strongyles
• During late winter and spring, the small strongyle
larvae living in the wall of an infected horse’s
cecum and colon come out of dormancy as
– numerous adult parasites within the intestines can
cause diarrhea, colic, and potentially death
• Horses usually infected by both large and small
strongyles simultaneously
– tend to have more small strongyles (produce more
eggs than the large strongyle worms)
Horse Strongyles
Taenia Tapeworm
• Cats and dogs are natural hosts for the tapeworm
– tapeworm starts off in small intestine
– each segment contains an independent set of organs
with new segments being created at the neck while
older segments drop off the tail
– the segments that drop off are full of eggs and are
shed in the feces
– an intermediate host (mouse, rabbit, deer, sheep etc.)
swallows one while eating
Taenia Tapeworm
Taenia Tapeworm
• The eggs mature into larva in the new host’s
– migrate into the blood supply and travel to liver,
irritating it
– travels to abdominal cavity where it forms a sac and
develops for 2 months
– In order to continue developing it needs a new host so
when the current host dies or is killed a predator, the
sac with the tapeworm may be consumed
– two months later, inside the new host, the larva
matures into an adult starting the cycle again
Taenia Tapeworm
• Cats and dogs are
natural hosts for
(uncommon for cats in
N. America – usually in
• Whipworm lives in
small intestine of host
– Eggs are shed in the
feces and into the
– Infected eggs are
– Larva hatches from eggs
in small intestine and
develop into adults for 210 days, starting cycle
over again

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