Endoparasites (not on exam 3 but final)

parasite definition

organism that lives off another organism at the expense of its host

general signs of acute parasitism

colic, unthriftiness, diarrhea, cough, lameness

what is the ‘most important‘ internal parasite in horses and why?

strongyle (blood worm), most common and causes the most damage

how does a horse get strongyles?

infective stage is swallowed while the horse eats/grazes/drinks contaminated waters. can also lick it off the stall walls, managers

what happens once the infected stage of the strongyle is ingested?

strongyle loses its sheath, enters the wall of the terminal portion on the small intestine, cecum, and large intestine

what happens after a short time of encapsulation in strongyles?

strongyle vulgaris larvae burrow into small artery walls and migrate to anterior mesenteric artery

what is the anterior mesenteric artery?

main supply of blood to small and large intestine

migration of strongyles:

causes disruption of blood flow, formation of blood clots in artery, irritation to arterial walls

irritation causes artery to become more restricted and BP causes wall to balloon out

what are thrombi?

vegetative clots in the vessel. released and lodge within the arteries of the intestine, heart, kidney, liver, and legs

symptoms of horses infected with/ strongyles

fever, poor appetite, rapid weight loss, depression, lethargy, colic, diarrhea, lameness, UNTHRIFTINESS

what happens after strongyle larvae remain in the ant mes art

after 120 days, they start migrating down arteries to lumen of large intestines.

after finishing maturation, they start to lay several thousand eggs/day

what are ascarids?

very large (15 in) yellowish-white worms. primarily affect young horses

how are ascarids passed?

passed through the manure of young foals and horses

infected eggs swallowed by eating grass, feed, water

where do ascarids burrow?

intro the wall of the small intestine where they migrate into the veins

describe the migration of ascarids

they are carried to the liver by the portal vein, after a week they trail to the lungs where they move to alveoli

they are then coughed up and swallowed, returning to small intestine where they mature

damage caused by migration of ascarids

worst is rupture of small intestine which is peritonitis

inflammation, scaring of liver/lung tissue, colic, decreased gut mobility which may trigger intussusception

how many eggs can ascarids lay

female won will lay up to 200,000 eggs/day

infected foal may pass 50 million eggs/day

clinical signs of ascarids

unthriftiness, pot belly, rough hair coat, slow growth, depression

cough and nasal discharge

what are strongyloides

threadworms

hair-like parasites 8-9mm thick

most commonly affect young foals

how are strongyloides acquired?

foals become infected by ingestion of larvae in the dam’s milk

larvae can be ingested during grazing

symptoms of strongyloides

diarrhea, weight loss, dehydration, poor appetite

describe the migration of strongyloides

larvae migrate to the lungs, up the trachea and are swallowed. reaching the small intestine they continue to mature until females lay eggs

how long is the life cycle of strongyloids?

2 weeks!

what are stomach bots?

larvae of botfly Gasterophilus that lay their eggs by attaching them to the hairs of the horse

describe the process of stomach bots from laid eggs to passing in manure

larvae attach and burrow into the tongue and gums of mouth, incubate there for 3-4 weeks.

after incubation the are swallowed and attach to lining of stomach

bots spend 9-10 months attached to stomach lining before passing out with manure

what damage to stomach do bots cause?

weakening of stomach lining, ulcers, abdominal distress and digestive disturbances, peritonitis, may obstruct feed passage from stomach to SI

what is intussusception?

where a portion of the intestine folds into itself, like a telescope sliding inward

clinical signs of tapeworms

poor growth, unthriftiness, digestive disturbances, peritonitis, impaction colic, rough hair coat

describe tapeworm infections

occurs in horses of all ages, eggs passed in manure and ingested by mites. mite larvae trail to ileum and attach

what are small strongyles

syathostomes

larvae that may remain dormant for a year, invade mucosa of large intestines

how many eggs can small strongyles produce?

over a million eggs/day

clinical signs of small strongyles

irritates intestinal tissue, diarrhea, weight loss, anemia

describe larval cyathostominosis

synchronous emergence of many larvae

sudden onset diarrhea, impaired gut mobility, weakness, muscle wasting, serious colic

4 classes of drugs for parasite control (plus 1 example for each)

benzimidazoles: safe-guard

macrocyclic lactones: ivermectin

tetrahydropyrimidines: strongid

isoqionoline: zimecterin gold

how do most anthelmintics work?

interfere with either the nervous system or energy/nutrient metabolism

tx cheat sheet for tapeworms

double dose with pyrantel (strongid)

praziquantel

tx cheat sheet for bots

ivermectin, moxidectin

tx cheat sheet for encysted small strongyles

moxidectin

5 d Panacur powerpac