Just a suggestion for you. Not that this should be your responsibility as I'm assuming you aren't the owner and keeper of the Gecko, but, maybe you could suggest having the geckos stool sample sent off for a relatively inexpensive test for cryptosporidium. Should that test come back negative, all your worries can be averted.

Yes, stick tail can be an indicator of crypto but it isn't a definitive for it.

Sadly, our first gecko suffered with stick tail and anorexia and we spent a small fortune trying to see him right, but he did pass away. Of what we're not totally certain, but it wasn't crypto as that test came back negative.

In the interim, just F10 anything and everything you think you may have touched. Spray the F10 on (watch the electrics, obviously), allow it a few minutes and wipe off.