AQHA MAGAZINE May / June 2020 AQHA May-June YB 2020 WEB LR | Page 63

PG.61
ARTICLE BY: DR JENNIFER STEWART - EQUINE VETERINARIAN AND CONSULTANT NUTRITIONIST
In terms of management priorities a
balanced diet, regular dental, vaccination
and farriery, establishing an effective
worm control program for your
pastures and horses – is part of being
an owner. Now let’s have a peep into
the lifestyles of horse worms – because
there-in lies the key to controlling them.
LARGE STRONGYLES wreaked havoc as a
leading cause of colic and death in horses mid
last century. Now however, the availability of
anthelmintics with high efficacy has resulted in
a marked decline in the prevalence of S. vulgaris,
equinus and edentata around the world.
LUNG WORMS are rarely found in horses
except those that share paddocks with
infected donkeys. Infected donkeys don’t
often show any signs but infected horses may
have increased respiration rate, coughing and
respiratory distress. Because they live in the
lungs, searching for eggs in the manure is futile
and your veterinarian may need to collect a
sample of fluid from the lungs for diagnosis.
PINWORMS reside at the very end of the
intestinal tract, laying eggs around the rectum
that cause intense itching and a rubbed tail
is often the hallmark of pinworms (Oxyuris
equi). Eggs resist desiccation, may become
airborne in dust, and remain viable in stables
for long periods. Transmission then occurs
via contaminated feedstuffs. Diagnosis is
by detection of operculated eggs, slightly
flattened on one side, on transparent
adhesive tape that has been pressed against
the perianal skin and then placed on a
microscope slide for examination or by the
chance observation of an adult worm in the
manure. Pinworms are yet to show resistance
to drugs and most wormers will treat the
infection. Because the eggs are laid on
the skin, they aren’t often found in a FEC.
THREADWORMS (Onchocerca cervicalis)
make your horse’s neck their home. The adults
rarely cause issues but the baby worms can
cause intense itching as they burrow down
to the lowest part of the chest and abdomen
where they hope to be picked up by a fly and
transported to a new horse. The lesions can
resemble a few other conditions, including
sarcoids, cancer, fungal skin invasions and
proud flesh. Your veterinarian may take a
biopsy for a definitive diagnosis and treatment.
BOTFLIES lay eggs on the leg and chest
hair which hatch when the horse licks them.
The larvae penetrate the gums and tongue
en-route to their home in the stomach -
occasionally they get lost in their travels and
end up in the brain, heart and lungs. They reach
maturity 10-12 months after infestation, pass
out into the manure and pupate to become
adult botflies. Removing eggs from the hair
and strategic worming with the correct drug
at the right time of year provide control.
ROUNDWORMS are quite gross - reaching
20-40cm in length and living in the intestines
they produce 0.5 to 2 million eggs a day!! The
important thing about roundworm eggs is
their extreme persistence in the environment.
Their thick wall (which protects them from
freezing cold, drying-out and disinfectants)
allows them to remain viable for up to 10 years
and their sticky coating enables them to adhere
to a variety of surfaces - including boots, stable
MAY/JUNE ISSUE ~ YEARBOOK 2020