According to the New York University Langone Medical Center, it is highly unlikely to contract trichomoniasis from sitting on a toilet seat. Trichomoniasis is a sexually transmitted disease that is transmitted by sexual contact between two people.
Medicine Net explains that trichomoniasis is a parasite that thrives in warm and moist conditions. This parasite cannot live long outside of a host. Even if someone that has trichomoniasis sits on a toilet and leaves the parasite behind, it is extremely unlikely to live long enough to be a concern.
Trichomoniasis can be contracted by both men and women, although the symptoms of the disease may vary. Women typically have the more prevalent and frequent symptoms.