Don't let your gecko ingest ivermectin though!
Not sure how it goes in geckos, but it can be deadly for Bearded dragons. Obviously, they're very different, but generally ivermectin used in horses as anti-parasite.

I know many people who've had success with it on snakes, applied externally as the other poster described.
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1.1.0 beardies
1.0.0 bloodred corn
0.1.0 striped anery corn
0.1.0 leopard gecko
0.1.0 golden gecko
0.2.0 mourning geckos
1.1.0 cats

soon to be:
BRB- thank you Dave!