L8: Parasite Control (Mallicote) Flashcards by Sara Prent

goal for 1st year of foal’s life in terms of parasite control

limit burden until young horses develop immunity

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major intestinal parasites

small strongyles (cyathostomes) (seasonal, winter in FL)
large strongyles
anoplocephala perfoliata (tapes)
ascarids (parascaris equorum) (year round in young horses)

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minor intestinal parasites

Gastrophilus intestinalis (bots)
Habronema muscae, Draschia megastoma (stomach worms)
Oxyuris equi (pinworms)
Strongyloides westeri (Threadworms)
Dictyocaulus arnfieldi (Lungworms)

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most clinically important parasite in the horse

small strongyles

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chars. of small strongyles

larvae migrate in cecum/colon walls for 4-6wks
may encyst for months-yrs
mature and encysted cyathostomes not significant in causing disease
emerging resistance

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CS of small strongyles

emergence of larvae –> inflammation –> hemorrhage, edema of cecum, colon –> colic and diarrhea

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chars. of large strongyles

migrate through abd. tissues (LIV, pancreas, arteries)
live in lumen of the gut
long prepatent period (6 mo.)
CS: colic, poor growth, weight loss
controlled well with ivermectin

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small strongyles aka

cyathostomes

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cyathostomes have widespread resistance to which antihelmintic(s)

fendendazole

oxibendazole

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pyrantel pamoate effective against:

-adult strongyles only (no larvae)
(some small strongyle resistance)
-adult ascarids
-tapeworms
-pinworms

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ivermectin effective against

strongyle larvae
adult and MIGRATING larvae of ascarids
bot larvae
stomach worms
pinworms (emerging resistance)
lungworms

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moxidectin effective against

strongyle larvae, including encysted larvae
adult ascarids
bot larvae
pinworms (emerging resistance)

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fenbendazole effective against

strongyle larvae, including encysted larvae only at special dose! (widespread resistance)
adult ascarids
pinworms

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chars. of parascaris equorum (roundworms)

adult horses develop immunity
eggs persist in env.
deadly in young horses
only parasite that causes impaction! (foals only)

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pathway of parascaris equorum (roundworms) lifecycle

small intestine –> lymphatics –> liver –> lungs –> pharynx –> small intestine (28d total)
-72-80d to produce eggs

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CS of ascarid infection

cough
diarrhea, colic
pot belly
rough hair coat
weight loss

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when can ascarid infection be diagnosed?***

after 80-90d of infection (by fecal float)

ascarids are resistant to:**

ivermectin
moxidectin
pyrantel

control of ascarids

2mo: deworm**
3mo: perform Fecal Egg Count Reduction Test
- deworm q60d with ivermectin or q30d with pyrantel, benzimidizole group until 8-12mo.

oxibendazole effective against

adult ascarids

- pinworms

chars. of anoplocephala perfoliata (tapeworms)

live at ileo-cecal valve

- can cause spasmodic colic, intussusceptions, ileal impactions

praziquantel effective against:***

tapeworms

tx of tapeworms

praziquantel, pyrantel
deworm foals prior to weaning
deworm adults 1-2x/yr

tx of botfly larvae

remove bot eggs from legs

- ivermectin or moxidectin

chars. of stomach worms (Habronema, Draschia spp).

- trans. by stable flies - cutaneous infection --> granulomas - tx with ivermectin and steroids for inflamm.

chars. of oxyuris equi (pinworms)

- live in small colon - female cements eggs to skin of anus - prepatent period 3.5-5mo. - difficult to find on fecal float; usually found as adult worms - emerging resistance to parasiticides

many parasites are resistant to what drugs?

oxibendazole | fenbendazole

20% of animals shed what percent of eggs

80%

strongyloides westeri =

threadworms

chars. of threadworms (strongyloides westeri)

- affects young foals - cause diarrhea - infection via milk - resides in SI - immunity developed by 4-5mo. - prepatent period = 5-7d

tx of threadworms (strongyloides westeri)

- mares: late gestation/foaling with macrocyclic lactones | - foals PRN

chars. of lungworms (dictyocaulus arnfeldi)

- donkeys can harbor infection with no CS - horses exposed via donkeys - CS: cough, dec. performance - tx with ivermectin

parasites of concern for adult horse

- stronglyes - tapes - gastrophilus (bots) - pinworms

dictyocaulus arnfeldi =

lungworms

parasites of concern for juvenile horse

ascarids strongyloides strongyles

ways to combat emerging resistance

- use fecal egg prod. testing to determine the effective anthelmintics - tx horses with high FEC only - tx during peak trans. season

fecal egg count cut-offs

500: treat

Fecal Egg count reduction test formula

(pre-treatment EPG - post-tx EPG)/pre-tx EPG x 100 -take samples pre and 10-14d post deworming

FECRT interpretation

For pyrantel and BNZ: >90%: good 80-90%: suspicious <98% is considered resistant

expected egg reappearance period (EERP)

interval b/w treatment and resumption of FEC >200 EPG

Rank EERP for benzimidazoles, pyrantel, ivermectin, moxidectin

benzimidazoles: 4wks pyrantel: 4 wks ivermectin: 8 wks moxidectin: 12 wks (gets shorter with inc. resistance)