Various bacterial (shigellosis, Campylobacter infection, or Salmonella infection), viral (hepatitis viruses A, B, and C), and parasitic (giardiasis or amebiasis) pathogens can be transmitted via sexual contact when there is risk of fecal-oral contamination. In order of decreasing risk, these types of sexual contact are:
Oral-rectal
Anal-genital
Oral-genital
Genital-genital intercourse
Although some of the above bacterial and parasitic pathogens may cause proctitis, they usually cause infection higher in the intestinal tract; symptoms include diarrhea, fever, bloating, nausea, and abdominal pain. Multiple infections are frequent, especially in people who have many sex partners and who engage in sexual activity that leads to direct or indirect oral-rectal contact.
Most of these pathogens can cause infections without symptoms; asymptomatic infection is the rule with Entamoeba dispar, which can develop in men who have sex with men (1, 2).
(See also Overview of Sexually Transmitted Infections.)
References
1. Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(4):1-187. Published 2021 Jul 23. doi:10.15585/mmwr.rr7004a1. Erratum: Vol. 70, No. RR-4. MMWR Morb Mortal Wkly Rep. 2023;72(4):107-108. Published 2023 Jan 27. doi:10.15585/mmwr.mm7204a5
2. Williamson DA, Chen MY. Emerging and Reemerging Sexually Transmitted Infections. N Engl J Med. 2020;382(21):2023-2032. doi:10.1056/NEJMra1907194
