The parasite passes from an infected person to an uninfected person during sex. In women, the most commonly infected part of the body is the lower genital tract (vulva, vagina, cervix, or urethra). In men, the most commonly infected body part is the inside of the penis (urethra). During sex, the parasite usually spreads from a penis to a vagina, or from a vagina to a penis. It can also spread from a vagina to another vagina. It is not common for the parasite to infect other body parts, like the hands, mouth, or anus. It is unclear why some people with the infection get symptoms while others do not. It probably depends on factors like a person’s age and overall health. Infected people without symptoms can still pass the infection on to others.
Sexually transmitted diseases (STDs) are among the most common infectious diseases in the United States. STDs can be spread through any type of sexual activity involving the sex organs, the anus or mouth, or through contact with blood during sexual activity. Examples of STDs include, chancroid, chlamydia, gonorrhea, granuloma inguinale, lymphogranuloma venereum, syphilis, genital herpes, genital warts, trichomoniasis, pubic lice (crabs), and scabies. Treatment is generally with antibiotics; however, some STDs that go untreated can lead to death.
^ Munson E, Kramme T, Napierala M, Munson KL, Miller C, Hryciuk JE (December 2012). "Female epidemiology of transcription-mediated amplification-based Trichomonas vaginalis detection in a metropolitan setting with a high prevalence of sexually transmitted infection". Journal of Clinical Microbiology. 50 (12): 3927–31. doi:10.1128/JCM.02078-12. PMC 3503002. PMID 23015673.
A draft sequence of the Trichomonas genome was published on January 12, 2007 in the journal Science confirming that the genome has at least 26,000 genes, a similar number to the human genome. An additional ~35,000 unconfirmed genes, including thousands that are part of potentially transposable elements, brings the gene content to well over 60,000.[16] 

Use of male condoms or female condoms may help prevent the spread of trichomoniasis,[22] although careful studies have never been done that focus on how to prevent this infection. Infection with Trichomoniasis through water is unlikely because Trichomonas vaginalis dies in water after 45–60 minutes, in thermal water after 30 minutes to 3 hours and in diluted urine after 5–6 hours.[23]
Trichomoniasis (trich) is an infectious disease caused by the parasite Trichomonas vaginalis.[2] About 70% of women and men do not have symptoms when infected.[2] When symptoms do occur they typically begin 5 to 28 days after exposure.[1] Symptoms can include itching in the genital area, a bad smelling thin vaginal discharge, burning with urination, and pain with sex.[1][2] Having trichomoniasis increases the risk of getting HIV/AIDS.[1] It may also cause complications during pregnancy.[1]

Blood in semen is also known as hematospermia. Blood in semen can be caused by many conditions affecting the tubes that distribute semen from the testicles (seminal vesicles) or the prostate gland. Symptoms that may accompany blood in semen include blood in the urine, fever, painful urination, pain with ejaculation, tenderness, and swelling in the testes or groin area. Urinalysis, ultrasound, and MRI may be used to diagnose blood in the semen. Treatment depends upon the underlying cause of blood in the semen.

^ Epstein, Aaron; Roy, Subir (2010). "Chapter 50: Vulvovaginitis". In Goodwin, T. Murphy (ed.). Management of Common Problems in Obstetrics and Gynecology (5th ed.). Wiley-Blackwell. p. 228. ISBN 978-1405169165. Archived from the original on 2017-02-15. In 80% of cases, the diagnosis of trichomoniasis is confirmed by microscopic examination of saline wet mount, with the observation of motile trichominondas; their shape is "football-like" with moving flagella.