Trichomoniasis is a common sexually transmitted infection caused by the protozoan Trichomonas vaginalis. In women, it causes vaginal infections and symptoms like discharge, itching, burning and odor. In men, it can cause urethral infections and burning after urination. While most men are asymptomatic, some experience discharge or burning. The infection is treated with antibiotics. Using condoms correctly during sex can help prevent transmission, as can limiting partners and abstaining from sex if infected.