Horses: Strongyles & Cyanthostomes

Question 1

large strongyles morphology

Answer 1

medium sized, males w copulatory bursa
prominent buccal capsule
adults parasitic in large intestine

Question 2

large strongyles life cycle

Answer 2

eggs passed in feces, develop of L3 in 2 weeks in ENVIRONMENT
L3 ingested while grazing
LARVAE MIGRATE EXTRAINTESTINALLY
Reproduce in L.I (ERP variance)

Question 3

strongylus vulgaris

Answer 3

larvae migrate in walls of small arteries
arrive in cecum/colon, mature and reproduce
6 month prepatent period

Question 4

strongylus equinus

Answer 4

larvae migrate in peritoneal cavity and liver
arrive in cecum/colon, mature and reproduce
8 month prepatent period

Question 5

strongylus edentatus

Answer 5

larvae migrate in peritoneal cavity and liver
arrive in cecum/colon, mature and reproduce
12 month prepatent period

Question 6

large strongyles clinical importance

Answer 6

disease in older foals during prepatent period
pathology: larval stages during long extra-intestinal migration
S. vulgaris most pathogenic
inflammatory response in host
adult worms suck blood
colic since blood supply interrupted, diarrhea when adults reach large intestine

Question 7

large strongyles clincal disease

Answer 7

fecal can be neg!
diagnose by clinical signs, age, and risk factors

Question 8

small strongyles morphology

Answer 8

smaller
males w copulatory bursa
anterior end w leaf crown
adults parasitic in L.I

Question 9

small strongyles lifecyle

Answer 9

eggs passed in feces & develop into L3 in 2 weeks
L3 ingested
larvae penetrate and encyst intestinal wall
Late L3 emerge intestinal wall, develop L4 and reproduce
eggs in feces 9 week post exposur

Question 10

small strongyles clinical importance

Answer 10

disease in foal BEFORE adult worms sexually mature
mass emergence of encysted parasites from wall of L.I= causes disease
fecal can be neg!
diagnose by clinical signs, age, risk factors
RED WORMS IN FECES

Question 11

strongyles diagnosis

Answer 11

eggs in fecal
large and small eggs are morphologically indistinguishable
ERP small 28days- 6/12 weeks
ERP large 6,8,12 months
FEC used to monitor drug effectiveness and pasture contamination

Question 12

deworming products

Answer 12

benzimidazoles
-beta-tubulin sythesis
IMZ
-nicotinic agonist
macrocylic lactones
-gated glutamate chloride channel
no resistance in large, small respond to macrocylic if ERP short

Question 13

interval dosing

Answer 13

most common
treatment of all horses at fixed intervals, no diagnostics
-shorter than ERP
-suppressive deworming to minimize contamination

Question 14

strategic dosing

Answer 14

treat all horses at fixed time of year, no diagnostics
fewer treatments, less intensity

Question 15

continuous daily treatment

Answer 15

daily administration of Pyrantel, no diagnostics
-kills L3 before they can invade tissue
-inhibits reproducing worms, low FEC
could be resistance

Question 16

selective treatment

Answer 16

treat horses above FEC threshold
allows portion of drug susceptible parasites to survive
fewer treatments, less intensity, reduce likelihood of resistance

Question 17

refugia

Answer 17

portion of parasite population not subject to drug selection pressure

Question 18

should targeting adults stop larval invasion or mass emergence?

Answer 18

NO!

Question 19

survival of parasite population

Answer 19

adult worms short lives
seasonally hostile environment inhibit reproduction and parasite transmission
-survive by arrested development

Question 20

minimum treatment objectives

Answer 20

target migrating large
-annually treat
control small population
-single yearly treatment when population arrested in tissues
-selective deworming to reduce pasture contamination
-preserves genetic diversity and susceptibility of worms to effective drugs

Question 21

T/F large strongyles migrate extra-inestinally

Answer 21

TRUE

Question 22

when does disease occur for small strongyles

Answer 22

when larvae emerge from hypobiosis in single or protracted event over a short period of time