Merck Manual

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Sexually Transmitted Enteric Infections


Sheldon R. Morris

, MD, MPH, University of California San Diego

Reviewed/Revised Jan 2023

Various pathogens—bacterial (shigellosis Shigellosis Shigellosis is an acute infection of the intestine caused by the gram-negative Shigella species. Symptoms include fever, nausea, vomiting, tenesmus, and diarrhea that is usually bloody... read more , Campylobacter infection Campylobacter and Related Infections Campylobacter infections typically cause self-limited diarrhea but occasionally cause bacteremia, with consequent endocarditis, osteomyelitis, or septic arthritis. Diagnosis is by culture... read more , or Salmonella infection Overview of Salmonella Infections The genus Salmonella is divided into 2 species, S. enterica and S. bongori, which include > 2500 known serotypes. Some of these serotypes are named. In such cases, common... read more ), viral (hepatitis Overview of Acute Viral Hepatitis Acute viral hepatitis is diffuse liver inflammation caused by specific hepatotropic viruses that have diverse modes of transmission and epidemiologies. A nonspecific viral prodrome is followed... read more A, B, and C viruses), and parasitic (giardiasis Giardiasis Giardiasis is infection with the flagellated protozoan Giardia duodenalis (G. lamblia, G. intestinalis). Infection can be asymptomatic or cause symptoms ranging from intermittent... read more or amebiasis Amebiasis Amebiasis is infection with Entamoeba histolytica. It is acquired by fecal-oral transmission. Infection is commonly asymptomatic, but symptoms ranging from mild diarrhea to severe dysentery... read more )—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

  • 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 practices that lead to direct or indirect oral-rectal contact.

Most of these pathogens can cause infections without symptoms; asymptomatic infection is the rule with Entamoeba dispar (formerly, nonpathogenic Entamoeba histolytica), which commonly occurs in men who have sex with men.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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