Exam 2 Flashcards
Symptoms of parasite
Weakness or unthrifty, emaciation, tucked up flank, potbelly, rough coat, colic, diarrhea, stunted growth, generally eat well and have a normal temp
Ascarids (name)
Large roundworms; parascaris equorum
Large strongyles
Bloodworms; strongylus vulgaris (anterior mesenteric artery; MOVE INTO ARTERIES AND MIGRATE TO CRANIAL MESENTERIC ARTERY WHERE IT BRANCHES FROM AORTA), strongylus edentatus (portal veins - liver), strongylus equines (liver)
Small strongyles
Small redworms; cyathostomes
Bots
Gasterophilus intestinalis (common bot), gasterophilus nasalis
Pinworms
Oxyuris equi (common pinworm; large spp; most damaging), probstmayria vivipara (minute pinworm)
Tapeworm Species
Anaplocephala perfoliata, anoplocephala magna, para-anoplocephala mamillana
Threadworms Species
strongyloides westeri
Ascarids (desc.)
small intestine, size of pencil, especially affect foals (horses over two develop immunity), larvae inflict damage to liver and lungs
Ascarid Life Cycle
Eggs pass out in feces; eggs live in environment for years; warm weather and damp eggs turn into larvae; foals eat larvae or infective eggs; go to lungs; migrate up trachea; coughed up and swallowed back down to GI; female lays 100,000 eggs in SI; eggs pass out in feces
Strongyles (desc.)
Most serious threat to health and life of horse; 40 different spp.; most all horses have them; small are most common; large are most danergous
Large Strongyle Life Cycle
Eggs pass out in feces; develop on the plants; 1st stage larvae; 2nd stage larvae (in soil or feces); 3rd stage crawl up grass; ingested by horse; larvae penetrate walls of SI cecum and colon; carried by blood to colon and cecum; migrate back through the walls into GI; attach to mucosa; takes 6 months; deworm with ivermectin to get both larval and adult stages
Small Strongyles Life Cycle
Cyathostomes; migrate to a lesser extent; pass directly to large intestine; become encysted in colon & cecum; emerge and return to gut (some attach and some remain free)
Bots (desc.)
Highly specialized parasite; attacks only horses or mules; two different spp in the US (Gastrophilus Intestinalis, Gastrophilus nasalis)
Bots Life Cycle
Four distinct states: egg, larvae, pupa, adult
Adult lays eggs on hairs of horse; fetlocks and knees; throat; inside nose; single egg for each strike; eggs hatch in 2-7 days; larvae enter horse’s mouth; molt and grow in mouth; pass into stomach and intestine and attach to lining for several months; release hold on GI lining and pass out in feces; nose bots reattach to rectum before dropping to ground; become pupae for 20-70 days; emerge as adult fly; adult fly does not eat; looks like honey bee when flying around horses
Pinworm (Oxyuris) (desc.)
Rectal worms
Pinworm Life Cycle
Female worms pass out with feces; deposit eggs on the way out or around anal region; eggs are swallowed by horses in feed or water; worms mature in LGI; young are alive little worms that live entire life cycle in the ventral colon
Pinworm Clinical Signs
Horses may rub tail head to itch when worms cling to anus; close relative is common in children
Tapeworms (desc.)
flat segmented worm; have intermediate host - orbatid mite; forms clusters in the ileocecal valve region of cecum; cause ulcerated lesions; common worm medicine are not effective against tapes (ivermectin) –> use praziquantel
Tapeworm Life Cycle
The eggs begin to develop while in the mites; horses accidentally eat grain mites with the developing eggs inside. These eggs become the head of the tapeworm and they attach to the intestinal lining and begin to grow segments that are filled with eggs; adults live in the large intestine and are made of the head and the segments that contain eggs; the segments break off and are passed in the stool, and are eaten by grain mites (orbatid mites) commonly found on permanent pasture
Threadworms (desc.)
Found in foals
Prevention & Control of Parasites
Problem is confinement; eat and sleep near feces; feces is the source of most all internal parasites; keep area clean and free of feces; feed away from feces
Parasite Control Program
Consult local vet; routine fecal examination; periodic treatment with anthelmintics
Anthelmintic Resistance
diminished effectiveness of wormers; evolution - survival of fittest, worms that survive reproduce; generation time is short. population is big - conditions for genetic changes in parasites; absorbs less of drug, breaks drug down with new enzyme, bypass pathway of drug
