L8: Parasite Control (Mallicote)

Question 1

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

Answer 1

limit burden until young horses develop immunity

Question 2

major intestinal parasites

Answer 2

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

Question 3

minor intestinal parasites

Answer 3

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

Question 4

most clinically important parasite in the horse

Answer 4

small strongyles

Question 5

chars. of small strongyles

Answer 5

• 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

Question 6

CS of small strongyles

Answer 6

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

Question 7

chars. of large strongyles

Answer 7

• 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

Question 8

small strongyles aka

Answer 8

cyathostomes

Question 9

cyathostomes have widespread resistance to which antihelmintic(s)

Answer 9

fendendazole

oxibendazole

Question 10

pyrantel pamoate effective against:

Answer 10

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

Question 11

ivermectin effective against

Answer 11

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

Question 12

moxidectin effective against

Answer 12

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

Question 13

fenbendazole effective against

Answer 13

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

Question 14

chars. of parascaris equorum (roundworms)

Answer 14

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

Question 15

pathway of parascaris equorum (roundworms) lifecycle

Answer 15

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

Question 16

CS of ascarid infection

Answer 16

cough
diarrhea, colic
pot belly
rough hair coat
weight loss

Question 17

when can ascarid infection be diagnosed?***

Answer 17

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

Question 18

ascarids are resistant to:**

Answer 18

ivermectin
moxidectin
pyrantel

Question 19

control of ascarids

Answer 19

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

Question 20

oxibendazole effective against

Answer 20

• adult ascarids

- pinworms

Question 21

chars. of anoplocephala perfoliata (tapeworms)

Answer 21

• live at ileo-cecal valve

- can cause spasmodic colic, intussusceptions, ileal impactions

Question 22

praziquantel effective against:***

Answer 22

tapeworms

Question 23

tx of tapeworms

Answer 23

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

Question 24

tx of botfly larvae

Answer 24

• remove bot eggs from legs

- ivermectin or moxidectin

Question 25

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

Answer 25

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

Question 26

chars. of oxyuris equi (pinworms)

Answer 26

• 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

Question 27

many parasites are resistant to what drugs?

Answer 27

oxibendazole

fenbendazole

Question 28

20% of animals shed what percent of eggs

Answer 28

80%

Question 29

strongyloides westeri =

Answer 29

threadworms

Question 30

chars. of threadworms (strongyloides westeri)

Answer 30

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

Question 31

tx of threadworms (strongyloides westeri)

Answer 31

• mares: late gestation/foaling with macrocyclic lactones

- foals PRN

Question 32

chars. of lungworms (dictyocaulus arnfeldi)

Answer 32

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

Question 33

parasites of concern for adult horse

Answer 33

• stronglyes
• tapes
• gastrophilus (bots)
• pinworms

Question 34

dictyocaulus arnfeldi =

Answer 34

lungworms

Question 35

parasites of concern for juvenile horse

Answer 35

ascarids
strongyloides
strongyles

Question 36

ways to combat emerging resistance

Answer 36

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

Question 37

fecal egg count cut-offs

Answer 37

500: treat

Question 38

Fecal Egg count reduction test formula

Answer 38

(pre-treatment EPG - post-tx EPG)/pre-tx EPG x 100

-take samples pre and 10-14d post deworming

Question 39

FECRT interpretation

Answer 39

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

Question 40

expected egg reappearance period (EERP)

Answer 40

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

Question 41

Rank EERP for benzimidazoles, pyrantel, ivermectin, moxidectin

Answer 41

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