There has been someone else who has posted on this Bulletin Board with BSI. When she posted she referred to her type of ich as "bathing trunk distrophy" so you may not have found it if you tried a search for BSI.

At the time of the post, she was in the Netherlands which, as a BENELUX country, is close to you. She said she was the only one in the Netherlands with BSI, just like you said you're the only one in Belgium. Since the post is from 2001, you may want to email her directly to initiate a contact. Her email is provided as part of her profile.

Good luck getting in touch.

Here is the link