Lice tend to stay embedded in the warm, dark areas where they thrive. Bodily contact spreads lice easily because the parasite transfers from one friendly environment to another. In other words, we have nothing to fear but fear itself. Making contact with urine, while extremely unpleasant, especially when it is not your own, does not expose you to disease of any kind. In fact, urine is used in some parts of the world as a disinfectant and is thought to have antibiotic properties.
Some people believe in drinking their urine and report definite health benefits.
Check the seat. If there are feces present, find another stall. If that's not an option, cover the feces with a good layer of paper towels. If there are a few drops of urine, or nothing at all, get a wad of toilet paper, enough to absorb but not soak through to your fingers, and wipe the seat all the way around. Now you have wiped away any wet spots, any lingering pubic lice, and all phantom diseases.