equine internal parasites- unit 3

gasterophilus intestinalis common name

common horse bot (the most common)

gasterophilus nasalis common name

chin/throat bot

Gasterophilus hemorrhoidalis

nose bot

gasterophilus intestinalis common name (for all three)

bots

phylum/class of G. intestinalis, G. nasalis, G. hemorrhoidalis

arthropoda- insecta

location of G. intestinalis

skin (eggs), stomach (3rd instar)

what does G. intestinalis affect?

equines everywhere

life cycle of G. intestinalis

flies lay eggs on horse’s hair, horse licks eggs or eggs hatch on their own and burrow into tongue or gingiva (hang out for 3-6 weeks and mature), larvae migrate to stomach and “overwinter” as “3rd instars”, bots are passed in feces where they pupate, emerge as adults 3-10 weeks later (typically cardiac region in the stomach)

external location of eggs for G. inestinalis

forelegs, belly, flank

external locations of G. nasalis

lays eggs under chin where they hatch and burrow into skin

external locations of G. hemorrhoidalis

black eggs laid around lips/nose where they hatch and burrow into skin

G. intestinalis pathology

sores in the mouth from larvae burrowing, GI hemorrhage/ulceration

clinical signs of G. intestinalis

nothing to anorexia and severe colic

diagnosis of G. intestinalis

necropsy- observe bots in stomach, observe eggs on hair, ulcers seen on mouth, fly troubles in the fall

treatment of G. intestinalis

ivermectins, wash legs or use a bot knife

common names for Habronema spp

summer sores, bursati, granular dermatitis

phylum/class of Habronema spp

nemathelminthes- nematoda

location of habronema spp

skin or stomach

what species does habronema spp affect?

equine

life cycle of Habronema spp

horses pass eggs that hatch into larvae, maggots of 2 species of flies eat the larvae (IH): musca domestica-house fly and stomoxys calcitrans- stable fly, nematode develop in the fly then travel out to the proboscis (fly mouth), deposited on lips, nostrils, or wounds of the horse

what is the IH for Habronema spp?

maggots of 2 species of flies (musca domestica- house fly and stomoxys calcitrans- stable fly)

what is the proboscis?

fly mouth

what are the 2 forms of Habronema spp?

gastric forms and cutaneous forms

gastric forms of Habronema spp:

irritate the lining of the stomach, produce large fibrous tumors in the stomach wall, tumors decrease digestibility; not going to have enough acid

cutaneous form of Habronema spp:

chronic, draining sores, larvae deposited in conjunctival sac (eyes), granular conjunctivitis

clinical signs of Habronema spp:

post mortem stomach form, cutaneous: biopsy- eosinophilic granuloma with caseous granules

treatment for Habronema spp:

ivermectin- skin will not often clear up once weather gets colder, gastric tumors are difficult to treat

what is the common name for Strongyloides westeri?

equine threadworm

phylum/class for Strongyloides westeri

nemathelminthes- nematoda

location of Strongyloides westeri

small intestine

what species does Strongyloides westeri?

horses, donkeys, zebras

life cycle of Strongyloides westeri

L3 infective larvae penetrate the skin (then tracheal migration occurs), L3 infective larvae are passed through MILK (then mucosal migration occurs), L3 infective larvae are eaten-rare (then mucosal migration occurs)

PPP for Strongyloides westeri:

10-14 days (earliest patent infection in foals- through milk)

Strongyloides westeri pathogenesis:

rarely affects horses older than 6 months old (inflammation and erosion of SI mucosa)

clinical signs of Strongyloides westeri:

acute diarrhea as young as 9 days of age in foals (usually self-limiting- goes away with time); if foal doesn’t die from dehydration/malnutrition, acts like parvo puppies minus the vomiting

is Strongyloides westeri zoonotic?

no

diagnosis of Strongyloides westeri:

(moms milk, babies poop); larvae seen in mother’s milk (not colostrum), embryonated eggs in fresh foal feces (mare does not pass eggs in poop)

treatment for Strongyloides westeri:

ivermectin, fenbendazole

common name of Parascaris equorum

equine ascarids or horse roundworms

phylum/ class of Parascaris equorum:

nemathelminthes- nematoda

location of Parascaris equorum

SI

what species does Parascaris equorum affect?

equine (usually under 2 years of age)

life cycle of Parascaris equorum:

(fecal oral route); eggs are passed in feces, eggs are consumed, tracheal migration occurs, larvae are coughed up and swallowed, larvae mature into adults in SI and produce eggs, no transmammary or transplacental infections in horses*

pathogenesis of Parascaris equorum

migrating larvae can damage the lungs and liver, large infections can cause perforation of the stomach or SI

clinical signs of Parascaris equorum:

respiratory signs: in young foals before patent period (coughing, pneumonia, pyrexia, nasal discharge, fever)

intestinal signs: colic, dull haircoat, undersized - due to stealing nutrition

diagnosis of Parascaris equorum:

ID eggs in fecal float

PPP for Parascaris equorum

10-13 weeks (longer than dogs/cats)

treatment for Parascaris equorum

Benzimidazoles, pyrantel pamoate, ivermectins, *****don’t use Moxidectin in foals under 4 months of age**

common name for Strongylus vulgaris (most common one), Strongylus edentatus, Strongylus equinus

large strongyles

phylum/class of large strongyles

Nemathelminthes- nematoda

location of large strongyles

cecum and colon mainly

what species does large strongyles affect?

equine

life cycle of large strongyles (focus on S. vulgaris):

ingested infective L3 larvae penetrate the SI wall, molt to an L4, penetrate arterioles (small arteries) and migrate to the cranial mesenteric artery (feeds the SI), migrate to submucosa of the cecum and colon, pass strongyle-type eggs

clinical signs of large strongyles

colic, diarrhea, exercise intolerance, thromboembolic colic (clot), rear-limb lameness/weakness, kidney failure, death

diagnosis of large strongyles

fecal float with strongyle-type eggs, Baermann to ID larvae, necropsy

PPP of large strongyles

6-7 months

treatment for large strongyles

ivermectin

what is the only nematode that develops within the arterial system?

large strongyle

what is another name for small strongyles?

cyathostomes

what is the most problematic parasitic nematode in equine in the United States?

small strongyles (cyathostomes)

phylum/class of small strongyles

nemathelminthes- nematoda

location of small strongyles

small intestine, large intestine, and cecum

what species does small strongyles affect?

equine

life cycle of cyathostomes

strongyle-type egg is passed in feces, L3 infective larvae is ingested, larvae become adults within 2-3 weeks, begin passing eggs with 42 days

PPP for cyathostomes

35-42 days

hypobiosis occurs with cyathostomes larvae for up to how many years?

3 (they encyst in tissue and emerge later)

pathology of cyathostomes

ingest blood= anemia, form nodules in the cecum, reduces GI motility, enteritis (diarrhea, anorexia, pain, signs of colic)

clinical signs of cyathostomes

loose stool, diarrhea, weight loss, death, colic(clinical signs occur in late fall or early spring; hypobiosis)

diagnosis of cyathostomes

strongyle-type eggs, increased EPG’s in the spring

treatment for cyathostomes

avermectins (cyathostomes are resistant to benzimidazoles), manage pasture (rotational grazing; but can’t control hypobiosis)

common name for Anoplocephala perfoliata, Anoplocephala magna, Paranoplocephala mamillana

Anoplocephala spp.

common name for Anoplocephala perfoliata 

medium horse tapeworm

common name for Anoplocephala magna

large horse tapeworm

common name for Paranoplocephala mamillana

dwarf tapeworm of the horse

phylum/class of Anoplocephala spp

(flat) platyhelminthes- cestoda (tapeworm)

location of Anoplocephala spp

SI, cecum, colon

what species does Anoplocephala spp affect?

equine

life cycle of Anoplocephala spp

Proglottids passes in feces, orbatid mite ingests the eggs (IH) from feces, tapeworm develops inside the IH for 2-4 months, orbatid mite is ingested by the equine

what is the IH for Anoplocephala spp?

Orbatid mite

PPP for Anoplocephala spp

6-10 weeks

pathology of Anoplocephala spp

ileo-cecal junction (hang out here) and cause inflammation, blockage, perforation

clinical signs of Anoplocephala spp

none to death (depends on parasite load)

diagnosis of Anoplocephala spp

fecal float, necropsy, PE, only 13% of worms shed eggs at any one time (significant when we see an egg)

treatment for Anoplocephala spp

any medication containing Praziquantel

control for Anoplocephala spp

keep horses out of the infected pasture for a year (snow will freeze egg= die), selective deworming

common names for Oxyuris equi

pinworms, oxyurids, or oxyuriasis

is Oxyuris equi zoonotic?

no

phylum/class of pinworms

Nemathelminthes- nematoda

location of pinworms

cecum, colon, rectum/anus

are pinworms in humans the same as in horses?

no

life cycle of Oxyuris equi

horse eats the egg that is on the ground, or in the food/water, mucosal migration of the larvae (stay within GI), adult female worm migrates to the anus and lays eggs on perianal skin, eggs are infective 3-5 days after being passed

PPP for Oxyuris equi?

4-5 months

treatment for Oxyuris equi

Panacur (fenbendazole), Benzimadole

clinical signs of Oxyuris equi

“rat tail”- hair is rubbed off, off feed, restless, sometimes no signs (if there’s not a lot or worms are on hair- if long enough)

diagnosis of Oxyuris equi

clinical signs, cellophane tape test- can see eggs under microscope

epidemiology of Oxyuris equi

not zoonotic, but contagious to other horses (Enterobius vermicularis is the human pinworm)

common name for Dictyocaulus arnfieldi

equine lungworm

phylum/class of equine lungworm

nemathelminthes- nematoda

location of equine lungworm

bronchi

what species does Dictyocaulus arnfieldi affect?

horses, zebras, and most common in donkeys in the U.S (problem in African zebras- more severe)