Lifecycles: Large
strongyle eggs can develop into infective larvae on pasture in as
little as three days. Once swallowed, the larvae drop their protective
coating, or "sheath" and migrate to different organs for
further development. Strongylus vulgaris larvae are very dangerous, moving through
the horse's arteries to the mesenteric artery, the main artery that
feeds the digestive system. S. vulgaris larvae continue to grow
in the mesenteric artery for about 4 months, then return to the large
intestine where they burrow into the intestinal cavity. After 6-8 months,
the worms mature and eggs are passed in the manure.
S. equinus larvae move to the liver for about 6
weeks. Then they migrate through abdominal organs to the
large intestine. After 9 months, adults mature and lay
eggs.
S. edentatus larvae also move to the liver, where
they remain for about 9 weeks. Then they move to the abdominal
cavity where they form nodules in the lining and the gut
wall.
How
It Gets Into Your Horse: Large strongyle larvae are swallowed
as your horse eats infected grass.
Dangers If Left Untreated: S. vulgaris cause
severe damage. Migrating larvae rough up artery walls,
leaving tracks where blood clots can form. Clots break
away from the wall and lodge into other blood vessels,
blocking blood flow to the intestine. Artery walls weakened
by larval damage are also prone to burst, leading to immediate
death. In the large intestine, large strongyles literally
bite off pieces of flesh, often leading to severe colic,
diarrhea, fever and anemia from the bleeding bite wounds. S.
equinus and S. edentatus can cause liver damage.
LARGE
STRONGYLES : Species & Stages |
|
S.
vulgaris - adults |
S.
vulgaris - L4 arterial |
S.
vulgaris - L5 arterial |
S.
edentatus - adults |
S.
edentatus - tissue |
S.
equinus - adults |
| fenbendazole* |
|
|
|
|
|
|
| ivermectin |
|
|
|
|
|
|
| moxidectin |
|
|
|
|
|
|
| oxfendazole* |
|
|
|
|
|
|
| oxibendazole* |
|
|
|
|
|
|
| pyrantel
pamoate |
|
|
|
|
|
|
| pyrantel
tartrate - daily |
|
|
|
|
|
|
| pyrantel
tartrate-single |
|
|
|
|
|
|
Based
on registered label claims and FOI summaries for each product
on file with the FDA; single-dose application.
* at a single larval dose
|
|
