Ashley R. Berthelot, DVM
Health maintenance, early detection
of problems, good diagnostics, and
high quality treatment translates to
long-term savings for the owner. In
addition, the overall well-being of
the horse improves and the
longevity of life and career can be
increased.
Establishing an effective
parasite control program
is probably second only
to supplying the horse
with clean, plentiful
water and high quality
feed.
Internal Parasites:
 Silent
thieves and killers
 Cause extensive damage
 Effect the horse from a dull haircoat and
unthriftiness to colic and death
 Can decrease resistance to infection
 Can rob a horse of valuable nutrients
Large
strongyles
Small strongyles
Roundworms
Tapeworms
Lungworms
Pinworms
Threadworms
Bots
Large Strongyles:
 Penetrate
lining of the bowel
and migrate along the blood
vessels that supply intestine
 Cause
unthriftiness, weight
loss, poor growth in young
horses, anemia, and colic
SmallStrongyles :
(cyathastomes)
 Burrow
into lining of intestine and
become encysted
 Cause severe damage to the lining
of intestine
 Can cause colic and diarrhea with
heavy infections
 Weight loss, slowed growth, poor
coat, and lack of energy
Roundworms (Ascarids):
Several inches long
 Most often a young horse problem
 In large numbers they can cause
impactions
 Migrate
through the internal
organs to the lungs, coughed up,
swallowed back into the digestive
tract to complete lifecycle.
 Can cause coughing, poor body
condition and growth, pot belly,
rough haircoat and colic.

Tapeworms:
 Can
cause mild to severe
colic
 Lifecycle
involves a tiny
mite as a host that horses
ingest in the grass, grain
or hay.
 Dull,
rough haircoat
 Decreased
energy
 Unthriftiness,
 Slow
loss of condition
growth in young horses
 Colic
 “Pot-bellied”
 Diarrhea
appearance
 Broad
spectrum
 Safe
 No
dewormers are 100% effective
 Not
necessary to kill every worm to
improve health, minimize risk of disease,
reduce pasture contamination, and
improve feed efficiency
Ivermectin (aka Eqvalan) is effective
against:
 Large Strongyles
 Small Strongyles, or cyathstomes, adult only
 Pinworms, adult and L4
 Ascarids, adult
 Hairworms
 Large-mouth Stomach Worms
 Bots
 Lungworms
 Intestinal Threadworms
 Summer Sores caused by Habonema and
Draschia spp.
Ivermectin is not effective against:
 Encysted
larvae
 Late
early third-stage cyathostome
third-stage cyathostome larvae
 Lumenal
larvae and adult cyathostomes
 Tapeworms
Fenbendazole
Safeguard)
•
•
•
•
•
(aka Panacur,
Large strongyles
Small strongyles or cyathostomes
Encysted third stage cyathostome larvae
Pinworms
Ascarids
Pyrantal
Pamoate (aka Strongid)
• Large strongyles
• Pinworms
• Large roundworms
• Small strongyles
3 Basic Types of Deworming Programs:
1. Continuous
2. Interval
3. Strategic
No deworming program suits all situations
The ideal program depends on the type, number
and ages of the horses, pasture management
and location
 Small
quantity of dewormer daily
 Effectively
prevents new infections picked
up during grazing
 May
not resolve existing infections
 Does
not kill bots
 Need
bi-annual supplemental deworming

Systematic, seasonal deworming program

Deworm horses six times a year (every 60 days)

Rotating different compounds based on seasonal
parasite prevalence

Rotating among the three main chemical classes of
compounds available (ivermectin, fenbendazole
and pyrantel pamoate)

Combat the parasites that are prevalent in that
season.

January - Ivermectin/Praziquantel (Equimax)

March - Pyrantel Pamoate (Strongid); fecal egg count
preformed 10 days post deworming

May - Ivermectin (Eqvalan)

July - Ivermectin (Eqvalan)

September - Double dose of Fenbendazole granules once
a day for 5 straight days;fecal egg count preformed 10
days post deworming

November - Ivermectin (Eqvalan)
www.greenelewis.com
 Deworming
based fecal egg counts
Aka: Test and Treat
Fecal Egg Counts

Microscopic examination of fresh manure for
parasite eggs

Results expressed in EPG (eggs per gram) of
manure

Fecal egg count of less than 200 epg suggests light
parasite load

500-1000 epg is moderate to heavy load

Negative fecal count does not mean parasite free
 Certain
compounds combat specific
parasites more effectively than others
 Repeat
 Correct
exposure can lead to resistance
seasonal compound selection can
decrease resistance and increase
protection
 No
great solution for preventing resistance
 One
way to try to avoid creating resistance is
to:
Test and Treat
Important to perform fecal egg
counts every 6 – 12 months to
measure the effectiveness of your
program.
 Prevent
overgrazing
 Reduce
pasture contamination
 Remove
manure regularly
 Mow/harrow
pastures periodically to
expose parasites to heat/sunlight
 Rotate
pastures with other livestock
 Keep
foals and weanlings separate from
yearlings and adults
 Use
a feeder for hay and grain rather than
feeding on the ground
 Consult
your veterinarian to set up
appropriate program
 Perform
fecal egg counts to monitor
effectiveness
Mankind's true moral test,
its fundamental test (which lies deeply
buried from view),
consists of its attitude toward those who
are at its mercy, animals.
Milan Kundera, 1929