Download Equine Parasites3

Equine Parasites
General Considerations
• Parasites are most successfully prevented through a combination of
management and therapeutic strategies
• Husbandry
• Decrease parasite burden in environment
• Therapeutic
• Deworming with proper product at proper intervals
Parasite Prevention
• Adequate pasture acreage
• Compost manure
• Cleanliness
• Pasture rotation
• Mixed grazing (cattle and horses)
Pasture Rotation
• Infective larvae on pasture decreases greatly over
the winter and also in hot, humid days of summer
• Move horses from old, infested pastures to ones
that have minimal numbers of infective larvae
• Deworm prior to moving
• Foals and young horses should go to cleanest
available pastures
Internal parasites
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The amount of clinical disease a horse will show depends on
three factors:
Type of parasite involved
Number of parasites involved
Host defenses. Young and debilitated animals more susceptible
Life Cycle of Parasites
• Eggs
• Larvae (immature worms)
• Adults (mature worms)
Life cycle of the parasite
• Eggs or larvae are deposited on
the ground in the manure of
infected horse
• The eggs and larvae develop in
the environment and are
swallowed while the horse is
grazing
• Larvae mature in the horse’s
digestive tract where most of
them become egg laying adults.
Internal parasites – Common
signs
• Poor growth
• Weight loss
• Decreased feed
efficiency
• Colic
• Diarrhea
• Pneumonia
• Death
Dull hair coat
Clinical sign – colic
Poor performance
Important Parasites in the horse
• Large strongyle (Stongylus vulgaris, S.edentatus, S.equinus)
• Small strongyle (Cyathostemes)
• Round worm (Ascarids)
• Bots (Gastrophilus spp)
• Pin worms (Oxyuris equi)
• Tapeworms (Anoplochephala)
• Threadworm (Strongyloides)
Large Strongyle
Strongylus vulgaris
• Blood worm- bloodsucking of the large instestine
• Most dangerous parasite of horses
• Causes thromboembolic colic, various degrees of anemia.
• Direct life cycle
• Larvae live in artery supplying blood to the intestines. Blood clots
form which block blood supply to the intestine
• First stage is the egg in feces or soil, molts to 2nd stage in feces or soil.
3rd stage becomes “sheathed” or sticks to walls, buckets, etc.
• When ingested by the horse the infective 3rd stage larvae of S.vulgaris
cast off there sheath in the lumen of the s. intestine and enter the wall
of the cecum and ventral colon. They curl up under the mucous
membrane and prepare to molt. After 8 days the molt is complete and
become a 4th stage larva and resume migration.
• 4th stage penetrate nearby small arterioles and wanders to the cranial
mesenteric artery, which supplies blood to the instestine. (this leaves a
path of inflammation, which can lead to thrombosis or occlude the
vessel) After 2-4 months they enter the surrounding tissue of the
intestinal wall and a final molt takes place and the immature adults (5th
stage) enter the lumen of the cecum and ventral colon , mature and
reproduce 6 months after original ingestion
Life Cycle
Adult large strongyle
Strongylus vulgaris,adults in equine
intestine “bloodworms”
After deworming “red worms”
• This verminous arteritis lesion is
from the cranial mesenteric
artery of a weanling Quarter
Horse colt. Verminous arteritis is
caused by the migration of larvae
of Strongylus vulgaris through the
blood vessels. It was once a
common cause of colic and death
in domestic horses.
S.edentatus, S. equinus
• 2 times as large as adults
• The 3rd stage of S. edentatus migrate to the liver, become
encapsulated and molt to the 4th stage in approx. 2 weeks. After
molting the larvae wander aimlessly in the liver for 2 months, leave
the liver by ligaments that hold the liver in position, wander for
months in the connective tissues, and 11 months (PPP) after
ingestion can be found in the lining of the cecum and colon.
• 3rd stage S.equinus encyst and undergo molt in the wall of the large
intestine. After molting they bore into the right half of the liver
which lies in contact with this portion of the large intestine. They
stay for 6-7 weeks, enter the pancreas and abdominal cavity where
the complete their development to adults. Reenter the lumen of the
large intestine and mate. (9mo. PPP)
Large and small strongyle
Diagnosis
• Diagnosis of mixed strongyle infection is based on demonstration of
eggs in the feces. Specific diagnosis can be made by identifying the
infective larvae after fecal
Large Strongyles
• Treat every 6 months
• Use Ivermectin or monoxidecin
Small Strongyle- Cyathostominae
• Numerous species of strongyles
(40)
• Direct Life cycle
• Larvae life in gut wall of large
intestine- therefore not as
pathogenic as large stongyle
• Cause damage to gut wall
resulting in G.I. upset, and severe
diarrhea.
• Internal parasites of highest
concern- encysted stage is not
affected by dewormers
• Very short life cycle 4 to 6 weeks
Life Cycle
Symptoms
• Colic
• Diarrhea
• Ill-thrift, loss of body condition
• Subclinical diseases is more common and may
result in greater economic losses
Diagnosis of Strongyles
• Fecal flotation- small and
large stongyles look similar on float.
Assume the worst and treat for large
• Baermann apparatus for larvae ID
• Necropsy
• Encysted cyathostome larvae in the large colon of a horse.
Treatment
• Many products available – nearly all horse wormers
are effective against adults in the GI tract
• Ivermectin, mixodectin, and fenbendazole effective
against migrating larvae
• Check fecal samples for eggs to gauge success of
worming program
Control of strongyles
• Use effective wormers routinely
• Avoid overgrazing pasture
• Use clean pastures for young animals
• Pile and compost manure
Pinworms
Oxyuris equi
• Adult pinworms lay eggs around the anus
• Direct lifecycle
• Eggs cause irritation and horses will rub their tails against objects
• Bare patches around the tail and perineum- pruritus ani
• Vague signs of abdominal discomfort if any
• Controlled by most wormers
Life Cycle
Pinworms
Diagnosis of Pin Worms
• Egg masses in perineal region
• Tail rubbing
• Eggs in feces (rare)
• Cellophane tape across anus
• Adults in feces
• Pinworms usually are the cause of the irritation that
leads to tail rubbing. Adult females deposit adhesive
egg masses on anal and perianal skin. Note the
broken hair at the base of the tail.
Adults in feces
Control of Pin Worms
• Thorough cleaning of stalls
• Fresh food and water
Treatment:
Moxidectin, Piperazine, Pyrantel
Stomach bots
Gastrophilus ssp
• Insects – the adult is a fly, the larvae live in the horse’s stomach
• Flies lay eggs on hair, they hatch and penetrate into the mouth tissue,
then migrate to stomach
• May cause stomach irritation and colic
• G. nasalis, G. hemorrhoidalis, G. intestinalis
Life Cycle
Bot fly and egg
Bot fly larvae
• Migrate thru the tongue
and esophagus after they
are ingested, and attach
themselves to the lining of
the stomach, where they
stay for up to 11 months.
In large numbers, they
contribute to gastric
(stomach) ulcers and
occasionally rupture of
the stomach.
gross lesion with adult worms, equine
stomach
• Mutual grooming leads to the ingestion
of bot eggs by horses
Diagnosis of Bots
• See eggs on hair and mane
• Endoscopy of stomach
• Necropsy
• Knowing flies are in area
Treatment of Bots
• Because flies are insects, only wormers that are effective against insects
will kill bots
• Ivermectin and moxidectin are effective
• Nits can be removed from hair before they hatch
• Nit removal combs, pumice stones
• Warm water with insecticide added
Public health significance
• Flies can lay eggs on human hair
• Larvae will hatch and burrow into skin
The stomach worms Habronema muscae H
microstoma , and Draschia megastoma
“Summer sores”
• The adults are 6-25 mm in size. Draschia are found in tumor-like
swellings in the stomach wall.
• The eggs or larvae are ingested by larvae of house or stable flies, which
serve as intermediate hosts. Horses are infected by ingesting flies that
contain infective larvae or by free larvae that emerge from flies as they
feed around the lips
Habronema
• If the larvae which are in the mouthparts of the immediate host are deposited in the open
skin well the fly feeds it can cause summer sores.
• Summer sores are ulcerated irritations. These lesions can cause soreness and itchiness and
become covered in a reddish-yellow tissue
• If the worms get deposited into the eye or the area around the eye it can cause a persistent
case of conjunctivitis.
Cycle
Lesions
Prepuce lesions (Summer sores)
Habronema muscae
• Diagnosis:
Skin scraping of lesions
Egg flotation
• Rx: Ivermectin, moxidectin
Ascarids - Roundworms
• Parascaris equorum
• Most common in foals/young horses –can cause impactation and colic
• Interfere with digestion and absorption of nutrients, notably protein
• Cause telescoping of intestine in foals
• Direct life cycle
• Larvae migrate through lungs where they can cause pneumonia
• Build up in large numbers in the anterior part of the small intestine