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Learn about common equine parasites, their life cycles, clinical signs, diagnosis, treatment, and prevention methods. Understand the importance of deworming, controlling parasites, and maintaining good stable hygiene.
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Parascaris equoru m Infective eggs are swallowed, they hatch and liberate infective 2nd stage larvae, which burrow into the wall of the small intestine and are carried to the liver by the portal vein. After migrating through the liver tissue, they enter the hepatic vein and are carried by the posterior vena cava to the lungs, where they break the into the alveoli, molt and are coughed up and swallowed, returning to the small intestine to mature. (3months) Eggs have proteinaceous layer and is sticky. Eggs adhere to stall walls, mangers, buckets, etc.
Ascarid • Can grow up to 12 inches in length within 4 weeks and block the small intestines.
Ascarids – Clinical Signs • Impaction colic – death • Pneumonia • Pot belly • Unthrifty appearance • Poor hair coat
Diagnosis of ascarids • Clinical signs • Fecal flotation • Necropsy
Control of Ascarids • Good sanitation • Eggs live in environment for many years • Avoid putting foals in same pastures year after year • Regular worming of foals and young stock
Treatment of Ascarids • Most common wormers are effective against ascarids (Safeguard, Panacur, Strongid, Ivermectin) • If a foal has a very heavy infection it should be wormed with less effective products to prevent impaction
Tapeworms • Three species of tapeworms are found in horses: Anoplocephalamagna , Aperfoliata , and Paranoplocephalamamillana • Found mostly in the cecum but may also be in the small intestine. • Young and older horses more susceptible -mite • Difficult to detect on fecal exam.
Tape worms (Anaplocephala) • Cause colic • Live at ileo-cecal valve • Disrupt motility • Use prazinquantel
Infection of A. perfoliata with intussusception of the ileum into the cecum.
A cluster of tapeworm segments at the ileocecal valve are of the cecum of a naturally infected horse.
Thread wormsIntestinal Threadworm • Strongyloides westeri – (strongyle-like) • Life cycle as short at 2 weeks • Infects young foals (2 weeks-6 months) • Larvae passed in mare’s milk to foals • May cause diarrhea in young foals • Immunity quickly developed • DOES NOT cause foal heat diarrhea • Strongyloides is zoonotic, cutaneous larva migraines.
Cutaneous larva migrans • Larva can penetrate foal’s skin to cause infection • May species penetrate human skin and cause problems in people as well
Diagnosis of Strongyloides • Fecal exam for larvae • Fecal culture • VERY rarely may see eggs
Treatment of Strongyloides • Worm mare prior to foaling to prevent larval migration to udder • Worm foals at 4 weeks of age
Control of Strongyloides • Sanitation • Keep stall dry to kill larvae
Diagnosis of internal parasites • Fecal egg counts can be very helpful negative fecal does not always mean no parasites • Monitor multiple horses on the farm at the same time • Some parasites are difficult to diagnose – tapeworms Smear, float, centrifuge, and Baermann apparatus
Baermann apparatus • Lung worms
Dewormers • None are 100% effective • 2 month interval (6 times a year) *think life cycles* • Use a broad spectrum product as basis for control (ivermectin, moxidectin) • Be sure to treat for tapeworms 1-2 time per year • Avoid creating resistance to anthelmintics *Double dose strongid *Product containing prazinquantel
Dewormers • Avermectins Ivermectin (Eqvalan, Zimectin, Equimectrin, Equimax) Moxidectin (Quest, Quest plus) • Tetrahydropyrimidines Pyrantal (Strongid, Rotation) • Benzimidazoles Febendazole (Panacur, Safeguard) • Prazinquantel
Parasite control • Manure removal at least 2x/week • Spread manure in hot weather away from fields where horses are grazing • Rotate Pasture- limit overgrazing (different species) • Group horses by age • Use feeder for hay and grain • Remove bot eggs from hair • Deworm new arrivals
