Sexually transmitted infections (STIs) are typically associated with symptoms localized to the genital region, such as discharge or sores. However, certain pathogens acquired through sexual contact can affect the gastrointestinal tract, leading to diarrhea. This occurs either because the infection directly targets the digestive system or because the pathogen compromises the body’s overall immune function. Persistent or unusual gastrointestinal symptoms may be the first indication of a sexually transmitted disease. This article addresses the specific infections that can cause diarrhea and explains the biological processes involved.
Key Sexually Transmitted Infections Linked to Diarrhea
The most significant sexually transmitted infection linked to diarrhea is Human Immunodeficiency Virus (HIV). Diarrhea can be an acute symptom during the initial infection phase, often appearing with flu-like illness within two months of exposure. In cases of advanced or untreated HIV, chronic diarrhea is common, frequently caused by opportunistic infections that flourish when the immune system is severely weakened.
Beyond HIV, a number of enteric pathogens are frequently acquired through sexual contact, particularly those involving oral-rectal exposure. These are often referred to as sexually transmissible enteric infections. Examples include the bacterium Shigella, which causes shigellosis and is known for producing profuse, sometimes bloody, diarrhea. Outbreaks of antibiotic-resistant Shigella have been observed, especially among men who have sex with men.
Parasitic infections like Giardiasis and Amoebiasis (Entamoeba histolytica) can be sexually transmitted, resulting in prolonged, watery diarrhea and abdominal pain. Localized bacterial infections of the rectum, such as Gonorrhea and Chlamydia, can cause inflammation known as proctitis, which sometimes leads to an urgent need to defecate and watery stools.
Lymphogranuloma venereum (LGV), a more aggressive strain of Chlamydia, can produce severe inflammation extending into the colon, leading to diarrhea and gastrointestinal distress. Hepatitis A and B viruses are transmissible through sexual contact and primarily affect the liver, but they can also present with non-specific symptoms like diarrhea and vomiting during the acute phase.
Mechanisms of Gastrointestinal Disruption
Diarrhea linked to sexually transmitted infections results from several distinct physiological processes. One mechanism involves the direct infection and resulting inflammation of the lining of the rectum and colon, known as proctitis or proctocolitis. Bacteria like Neisseria gonorrhoeae and Chlamydia trachomatis (including LGV strains) infect the rectal mucosa, causing cellular damage. This inflammation interferes with the colon’s ability to absorb water, leading to loose stools.
Another mechanism is direct viral activity, such as in HIV enteropathy, where the virus or its proteins cause changes to the intestinal lining. HIV targets and destroys immune cells in the gut wall, disrupting the local immune defense and compromising the mucosal barrier. This damage results in increased intestinal permeability and malabsorption, which contribute directly to chronic diarrhea.
The third mechanism is immune compromise, which is particularly relevant in untreated HIV infection. As the virus depletes the body’s CD4 T-cells, the immune system can no longer control common environmental or latent pathogens. This allows opportunistic microbes to thrive in the gastrointestinal tract, including parasites like Cryptosporidium and Microsporidium, or viruses such as Cytomegalovirus (CMV). These opportunistic infections cause severe, chronic diarrhea and fluid loss through extensive damage to the intestinal cells.
Seeking Testing and Treatment
If persistent diarrhea occurs, especially in combination with other unusual symptoms or following a recent sexual exposure, medical consultation is necessary. The diagnostic process begins with a detailed sexual history to assess the risk of exposure to specific pathogens. Clinicians may request a stool sample analysis, which is crucial for identifying enteric pathogens such as Shigella, Giardia, Entamoeba histolytica, and opportunistic infections like Cryptosporidium.
In addition to stool tests, a healthcare provider will recommend a comprehensive STI panel, including blood tests for HIV and syphilis, and swabs for Chlamydia and Gonorrhea collected from all potentially exposed sites, such as the rectum. Testing helps accurately pinpoint the microbial culprit, as many non-STI conditions also cause diarrhea. Early diagnosis of an STI-related cause is important because the condition is treatable and identifying the pathogen prevents further transmission.
Treatment is specific to the identified infection. Bacterial infections like shigellosis or localized Chlamydia and Gonorrhea are treated with appropriate antibiotics. Parasitic infections require antiparasitic medications, while viral infections like HIV necessitate highly active antiretroviral therapy (HAART). Effective HIV treatment manages the viral load and restores immune function, which resolves diarrhea caused by opportunistic infections. Notifying sexual partners about a diagnosis is a necessary public health measure to ensure they receive testing and treatment, curbing the spread of the infection.