Sexual Transmission of Enteric Protozoa and Helminths in a Venereal-Disease-Clinic Population

We examined the prevalence of enteric protozoan and helminthic infections and the associations between infection and gender, sexual preference, and sexual practices in 180 consecutive patients at a venereal-disease clinic. Of 163 men, 29 were infected with one or more enteric parasites. None of the 17 women had an enteric infection. The prevalence of infections with Entamoeba histolytica or Giardia lamblia (or both) was 21.5 per cent in homosexual men, 6.2 per cent in bisexual men, and 0 in heterosexual men. There were significant associations between oral-anal sex and infection with E. histolytica (P<0.01) or with helminths (P<0.05). Homosexuality and oral-anal sex were the most important risk factors for E. histolytica, G. lamblia, and helminthic infections. We conclude the “hyperendemic” enteric protozoan infection rates in homosexual men are related to three factors: the original endemic level in the general population; the prevalence of sexual acts that facilitate transmission; and the frequency of exposure to an infected person. (N Engl J Med. 1981; 305:603–6.) SINCE the first published observation (in 1968) of a relation between enteric protozoan infections and sexual behavior,₁ there has been increasing recognition that giardiasis and amebiasis can be sexually transmitted. These diseases were previously considered to be exotic illnesses related to foreign travel or to contaminated food or water. However, the importance of person-to-person spread of intestinal protozoa, particularly among homosexual men, is now generally acknowledged._{2 , 3} Physicians have reported a several-fold increase in the case incidence of amebiasis in San Francisco and New York City in the past few years, and public-health officials in both cities have speculated that this. . .