Sexually Transmissible Infections in Clinical Practice

31. A Gay Man with Diarrhea

Alexander McMillan^{1, 2}  

(1)

Department of Genitourinary Medicine, NHS Lothian, Edinburgh Royal Infirmary, Edinburgh, Uk

(2)

University of Edinburgh, Edinburgh, Uk

Alexander McMillanFormerly, Consultant Physician, part-time Senior Lecturer

Email: a.amcmm@btinternet.com

Abstract

Samuel, a 24-year-old British, man attends a Gay Man’s Sexual Health clinic for investigation of troublesome diarrhea. For the preceding 10 days he has been passing loose watery stools about five times per day. The stools are offensive, float on the surface of the water in the toilet, and are difficult to flush away. He has not, however, noticed blood, pus, or mucus in the stools. His appetite has been poor, and he has had some upper abdominal discomfort with increased flatulence. He is otherwise symptomless, in particular he has not felt feverish. He has not traveled outwith the United Kingdom within the past 2 years. There is no past history of gastrointestinal disorders. He has been fully immunized against hepatitis A and B.

Samuel, a 24-year-old British, man attends a Gay Man’s Sexual Health clinic for investigation of troublesome diarrhea. For the preceding 10 days he has been passing loose watery stools about five times per day. The stools are offensive, float on the surface of the water in the toilet, and are difficult to flush away. He has not, however, noticed blood, pus, or mucus in the stools. His appetite has been poor, and he has had some upper abdominal discomfort with increased flatulence. He is otherwise symptomless, in particular he has not felt feverish. He has not traveled outwith the United Kingdom within the past 2 years. There is no past history of gastrointestinal disorders. He has been fully immunized against hepatitis A and B.

In the past 3 months he has had about 15 different and unknown male sexual partners. He has had protected receptive and insertive anal intercourse with six of these men, but he has had unprotected oral–genital and oral–anal sex with each man. His most recent sexual contact had been about 14 days prior to the clinic attendance.

31.1 What Sexually Transmissible Infections Would You Consider in the Differential Diagnosis?

Sexually transmissible infections can cause a variety of intestinal disorders, particularly among men who have sex with men (MSM), as shown in Table 31.1. Bacteria such as Neisseria gonorrhoeae, Chlamydia trachomatis, and herpes simplex virus can be transmitted by receptive anal intercourse and cause distal proctitis. Oral–anal sex (rimming) can result in the acquisition of organisms transmissible by the fecal–oral route and shown in Table 30.1 as possible causes of enteropathy and proctocolitis.

Table 31.1

Sexually transmissible causes of enteropathy, proctocolitis, and distal proctitis.

^aLGV = lymphogranuloma venereum.

^bIn severely immunocompromised patients (in the context of HIV infection, CD4⁺ T-cell count <100/mm³).¹

^cSexual transmission possible but not yet described in the literature.

The clinical features are not those of a distal proctitis (see Case 20), in which constipation is a more likely symptom than diarrhea, and in the absence of blood, pus, and mucus in the stools, proctocolitis is unlikely. Small intestinal infection with Giardia intestinalis or Cryptosporidium spp., however, is a possible cause of this man’s symptoms. The pre-patent periods of giardiasis and cryptosporidium infections are estimated to be between 12 and 19 days, and 1–14 days, respectively. Self-limiting diarrhea may also be a feature of primary HIV infection, occurring on average about 14 days after infection. There are, however, usually associated symptoms such as fever, sore throat, swollen lymph glands, arthralgia, and a skin rash. Rotaviruses, adenoviruses, particularly Group F, and small-round-structured viruses can be transmitted by the fecal–oral route, and MSM who practice oral–anal sex may therefore be at risk. The pre-patent period of acute viral gastroenteritis is short – usually 1–2 days, but sometimes up to 7 days in the case of rotavirus and adenovirus infection – and the diarrhea usually lasts for less than 1 week. This diagnosis is therefore unlikely.

Samuel looks well, with no evidence of weight loss. His temperature is 36.5°C. There is no skin rash, and the mouth and pharynx appear normal. Significant enlargement of the superficial lymph nodes is not found. The abdomen moves well with respiration, and there is no tenderness or guarding. There are no abdominal masses, and neither the liver nor spleen is palpable. The perianal region is normal. Anoscopy shows watery stool in the lumen of the rectum whose mucosa appears normal: the vascular pattern is normal, the mucosa does not bleed easily, and mucopus is not noted in the lumen.

31.2 Do the Clinical Findings Help Narrow the Differential Diagnosis?

There is no evidence of distal proctitis, but the clinical findings support the conclusion that he has an enteropathy.

Microbiological tests for gonococcal, chlamydial, treponemal, and HIV infections are undertaken as described in Case 4, and a stool sample is obtained for microbiological investigation, including parasitology.

Samuel attends the clinic 1 week later. His symptoms remain unchanged. The tests undertaken at the initial attendance yielded negative results for N. gonorrhoeae, C. trachomatis, Shigella spp.,Campylobacter spp., Salmonella spp., and enterotoxigenic Escherichia coli. Neither trophozoites nor cysts of G. intestinalis were detected by microscopy, and oocysts of Cryptosporidium spp. were not seen in a stained preparation of the stool sample. Serological tests for syphilis, including an anti-treponemal IgM enzyme immunoassay (EIA), were negative, and a combined antigen/antibody EIA for HIV was also negative.

31.3 How Do You Interpret the Results of the Parasitological Investigations?

The absence of trophozoites or cysts of G. intestinalis in a single stool sample does not exclude infection with this protozoan. Multiple stool samples (at least three) should be tested before a negative result is reported. Direct immunofluorescence and immunoassays that have high sensitivity, specificity, positive, and negative predictive values when compared with the standard microscopical diagnostic methods have become available commercially. They are generally considered to be more sensitive than microscopy. False negative results in the antigen detection methods, however, may result when there are low parasite numbers, and repeat testing is recommended when a negative result is obtained but the diagnosis is strongly suspected. These tests may remain positive for some time after the parasite has been cleared. Some commercially available assays provide for the simultaneous detection of Giardia and Cryptosporidium.

A further three stool samples were sent to the laboratory. Cysts of G. intestinalis are found in the third specimen. Oocysts of Cryptosporidium spp. were not detected, and culture of these specimens yielded negative results for bacterial pathogens.

Giardia intestinalis (also known as G. lamblia or G. duodenalis) is an intestinal flagellated protozoan. The trophozoite (Fig. 31.1) is pear shaped, and the ventral surface is modified into an adhesive disc by which it attaches to the epithelium of the duodenum and jejunum. There are two oval nuclei and eight flagella. The trophozoites multiply by binary fission. Some pass down the small intestine and encyst. It is the cyst (Fig. 31.2) that is the infective stage. Cysts are passed out in the feces, and, after ingestion by the host, they excyst shortly after entering the upper small intestine. Two small trophozoites emerge from the cyst, divide, and become normal trophozoites.

Figure 31.1.

Trophozoite of Giardia intestinalis.

Figure 31.2.

Cysts of Giardia intestinalis.

Giardiasis is an infection found in both temperate and tropical countries, particularly where sanitation is poor. It is estimated that 10–100 cysts are required to initiate infection (more than 300 × 10⁶ cysts may be found in 1 mL of feces from some symptomatic patients). The infection is acquired by the ingestion of cysts in food or drink, and by direct fecal spread from one person to another. In the context of sexual transmission, oral–anal intercourse is probably important. Many infections are symptomless and transient, but in other individuals diarrhea results and malabsorption may be a feature. Untreated, symptoms usually resolve after a variable interval of up to 3 months.

31.4 How Would You Treat Samuel?

Table 31.2 indicates recommended treatment regimens for giardiasis.

Table 31.2

Recommended treatment regimes for giardiasis.

Samuel is treated with metronidazole 2 g daily by mouth for 3 days. He is warned about the interaction between the alcohol and the drug (see Case 10). What further action would you advise?

As it is probable that Samuel acquired Giardia through sexual contact, partner notification is indicated. If possible, all partners within the preceding month should be screened for symptomatic infection, and treated if necessary. After treatment, three stool samples, taken not less than 24 h apart should be obtained to confirm cure. In some patients, intestinal symptoms may persist for several weeks after eradication of infection. This is attributed to slow recovery of function of the intestinal epithelium.