Are some people more prone to getting schistosomiasis?

Exposure. Parasitic illness, "snail fever". Endemic in some parts of africa, caribbean, middle east, asia, s. America. Depending on type can cause liver or urinary problems. Exposure to standing fresh water- (including man-made lakes, either from work, recreation, domestic chores. Avoidance is key on an individual level; bigger issues on a societal level.