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.

Life Cycle

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

Ascarid impactation and rupture

Parascaris equorum

Ascarid in the bile system of the liver

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: Anoplocephala magna , A perfoliata , and Paranoplocephala mamillana 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

Difficult to detect the eggs on fecal sample

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 worms Intestinal 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.

Thread worms

Can be free living in the soil

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

Stronglyoides egg (larvae moving)

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

Run a fecal on me before you pump me full of medication….