Trichomonas vaginalis is a sexually transmitted infection (STI). It is sometimes referred to as trichomonas or trichomoniasis. It is also popularly known as TV. This could spread from one person to another during sex, or through shared sex toys if you do not wash them or use a new condom each time they are used. It is caused by a tiny parasite which causes an infection, affecting the vagina and urethra in women and in the urethra in men. Symptoms rarely appear, showing only one month after coming into contact.