It's not that I don't associate it with an ethnicity so much as I don't do it automatically. Sure, if we're talking about sickle-cell, then yeah, one of the first things I'll say about it is that it disproportionately affects black people. But this book? Not talking about sickle-cell - the disease is mentioned in passing. I was thinking of everything in relation to Shadow, so when I read that Shadow's mother had a debilitating disease, the thing I thought it about was how it would have impacted him as the main protagonist and POV character, not what the disease would have meant for/about his mother.