Yes you can use it topically and the cool thing about Ivermectin
is it kills both internal and external parasites.
1 ml (or cc) on the skin for a goose, 1/2 ml for a chicken.
I put it on their back between their wings.
SO easy to use and they get a complete dose unlike if you put it in water
like I have heard some suggest
Make sure to give a 2nd dose a couple weeks after you've administered the first dose.
Late Autumn is a good time to deworm livestock.
Doing it after the ground freezes will prevent them from picking up new parasites.
There's a link on my websites tip page for a website that explains this in detail.
Hope this helps.