Ivermectin was initially developed for use in cattle and horses,to treat both internal and external parasites.
It has been used in snakes and lizzards,via injection,oral,and spray form.Allthough i wouldn't recomend the first two aplications,the diluted spray seems to be relativly harmless..and works quite well..we used to use it at the zoo with no ill effects at all.
However it can cause problems in all chelonians,apparently it has the ability to cross the blood /brain barrier in tortises and aquatic turtles,causeing neurological disorder/disease.
If you choose to go with the spray method...wich i think is your best bet..mix 1/2cc of the 1% ivomec to 1 quart of tap water.
spray the cage and animal,repeat 7-10 days later if necessary.
Also frequent substrate changes and cage cleaning will also be necessary.
hope this helps.