I got a leech bite around 7 months ago. Used soframycin ointment and it didn't feel anything, but now it has become a black mark and doesn't reduce. There's no pain or burning sensation, but I get a lot of itching in my ankle where the bite is, I'm using Fusiwal ointment suggested by my doctor but that doesn't reduce the bite mark, can you please suggest what further checkup or medication I should be using. Is the bite going to be poisonous?