Below is a quote from BBC News.
Am wondering if anyone else here has used this particular honey for their crabs,as I haven't found any thread on medicinal honey being used for this purpose. I guess in the end anything is worth a try."It works on bacteria, fungi, protozoa. We haven't found anything it doesn't work on among infectious organisms."
This is a link for one site with useful information on Manuka honey;
http://news.bbc.co.uk/1/hi/health/3787867.stm