Various pathogens—bacterial (Shigella, Campylobacter, or Salmonella), viral (hepatitis A, B, and C viruses), and parasitic (Giardia sp or amebae)—are transmitted via sexual practices, especially those that can involve fecal-oral contamination. In order of decreasing risk, these practices are oral-rectal, anal-genital, oral-genital, and genital-genital intercourse.

Although some of the above 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 with many sex partners. Most of these pathogens can cause infections without symptoms; asymptomatic infections are the rule with Entamoeba dispar, which commonly occurs in homosexual men and was previously known as nonpathogenic Entamoeba histolytica. For diagnosis and treatment of these infections, see elsewhere in The Manual.

Last full review/revision November 2008 by J. Allen McCutchan, MD, MSc