[cypher]

There's no way of telling clearly how big the holes are from the photo but it does look similar to the ones I've seen with something like 1.5cm spacing, I can see it says non stick though so make absolutely sure your hams can't get close to it at all.

Sneezing doesn't sound too good, keep a close eye on them in case they have caught a cold.
Either that or check your substrate isn't too dusty.