Small organisms that live on or in and derive their food from a host organism, such as a horse Be beneficial or detrimental Primary management goal is to control harmful internal parasites that can lower efficiency, performance, digestion and can even kill a horse Symptoms: May develop slowly Weakness Unthrifty appearance Emaciation “potbelly” Tucked up flanks Rough hair coat Slow growth

Spend their life cycle in the host Generally be classified as roundworms Six groups of roundworms: Ascarids Small Strongyle Large Strongyle (Bloodworms) Threadworms Pinworms Stomach Worms Ascarids, strongyle, and pinworms are major concern for the horse An insect that has an internal stage of development in the horse is the stomach bot To minimize that life cycle must be broken

AKA large roundworms Largest parasites that live in the horse Grow 30.5 to 38.1 cm (12 to 15 in) and are about the diameter of a lead pencil Primarily problem in young horse Older horses develop immunity

Life Cycle: Starts with mature female laying eggs in the SI Eggs pass out in the feces After they are outside the horse (~2wks), develop into the infective stage Eggs are swallowed when horse eats grass, feed and feces and drinks water Eggs then hatch into larvae stage Larvae then burrow into the wall of the SI Enter bloodstream from SI where that are carried to the liver and heart Migrate through the liver and heart, and veins that drain these organs, and travel to the lungs From the lungs they are coughed up and swallowed Upon reentering the SI they mate, females produce eggs

Damage liver, heart, and lungs Heavy infestations can block the SI causing colic May rupture intestinal lining, causes peritonitis and death Eggs are resistant to environmental conditions and can live for years before ingested Control requires thorough cleaning of stalls before foaling, preventing fecal contamination of feed and water buckets, frequent manure removal, frequent drug treatment

Most serious threat to horse’s health Severe infestation is common in horses permanently grazed on pastures Symptoms (condition is called strongylosis): Low appetite Anemia Emaciation Rough hair coat Sunken eyes Digestive disturbances “Tucked up” appearance

Life Cycle: Eggs are laid in intestines Pass out in feces and continue to develop 1-2 days After ~ week, larvae become infective, move up blades of grass, horse ingests Migrate through various body tissues causing extensive damage After they return to the small intestine, they attach to the lining of the gut where they mature Cause arterial damage and the development of small blood clots in the arteries Aneurysms may develop and burst Horse will bleed internally and die May break loose and become lodged in smaller arteries blocking blood flow to certain tissues and organs

Management control involves removal of manure at least 2x weekly Infective larvae are not as resistant to the environment as ascarid eggs and usually cannot live beyond one year Pasture rotation and resting the pasture for a year helps Routine deworming with appropriate drugs must be used to keep larvae numbers and damage at a minimum Grazing cattle and sheep help remove them

Do not cause must damage to the horse Mature worms live in the colon of the LI Can be 7.6 cm (3 in) long Life Cycle: Females lay eggs in the colon, pass out in the feces Or females lay eggs on the skin around the anus Causes itchy sensation Eggs are sticky and therefore stick on walls, feed buckets, and other equipment contaminating the environment and increasing the chances for re-infestation Controlled by manure removal and medication

Three species that affect horses Adult bot fly resemble a honey bee Bot flies are active from first part of summer to first hard frost

Gasterophilus intestinalis Eggs are yellow and can easily be seen Life Cycle: Laying eggs in the hairs of the horse’s legs, chest, belly, and neck Eggs hatch after about 1-2 weeks, when exposed to moisture, warmth and friction Condition is met when the horse licks the area Upon hatching, they enter the mouth where they enter the mouth and burrow into the tongue and are eventually swallowed Inside the stomach, attach to lining where they mature Detach themselves and pass through the digestive tract Develop in the pupae stage and pass out in feces Outside they burrow in the ground, develop into the botfly and emerge in warm weather Takes about one year

Gasterophilus nasalis Lay eggs around the chin and throat area Eggs incubate in 4 – 6 days and hatch without stimulation Larvae crawl into mouth and enter gum tissue around teeth Leave mouth and enter stomach, attach to stomach lining and mature Rest is similar to Botfly

Gasterophilus hemorrhoidalis Lay black eggs on the nostrils and lips Hatch in 2 – 4 days without stimulation Burrow into the inner lip membranes After 5 – 6 weeks they enter stomach. Rest is similar to Botfly

Cause stomach damage and rupture to stomach Control or prevent heavy infestation, kill adult flies, remove eggs and deworm Once eggs are laid, they can be removed from the hairs by scraping them with a knife or sandpaper Should be treated with anthelmintic medication at least 4x/year First frost should kill them, no new larvae will enter the horse