OK,
Well I hear what you are saying, but most smallholders are not qualified pharmaceutical experts, able to make such decisions on the safety or otherwise of certain chemicals or the correct dosage or the withdrawl period.
If administered or prescribed by a Vet than that is fine and reasonably safe, and his liability insurance will cover him for any ill effects to livestock or people.
Surely, nobody in their right mind would use an unlicenced product that they alone decided was safe without professional advice (or prescription) and then go on to sell their eggs / meat to the public? and also recommend that others do the same....
My final words on the subject, as Im sure you will use what you want at the end of the day, and if the infestation is that bad then there are approved commercial products available to treat large areas.
Thanks