The only Lupus I've heard of is a nasty type of disease. A friend of mine suffers from it and she has to have kimo and take about 50 different tablets a day.
I don't know much about it but I do know is that lupus erythematosus, one of three (I think) types of lupus which humans can have has several subcategories to it. Two of these subcategories have been seen in dogs. It's an autoimmune disorder and is caused by genetics so I'd have thought it's very probably inherited and has nothing to do with pathogens found in water.