Roughly one in four heterosexual men have anal human papillomavirus (HPV) infection and, in many cases, a cancer-causing type of the sexually transmitted wart virus is present, a study shows.

Certain strains of HPV, which can be transmitted from male to female partners, are responsible for most cases of cervical cancer. Although much is known about HPV infection in women, this is not the case in men.

“Only two studies have reported anal HPV prevalence in heterosexual men,” Alan Nyitray, from the Arizona Cancer Center in Tucson, who led the current study, told Reuters Health. “The first study from Amsterdam recruited men in an STD clinic. The second from Sao Paulo recruited men who were husbands of women with confirmed cervical HPV infection. Our study is different in that we primarily recruited men from two universities, in addition to the general community.”

In their study of 222 men, the researchers found that the prevalence of HPV in the anal canal was 16.6 percent. The prevalence of HPV around the anus (the “perianal” region) was 21.3 percent.

Surprisingly, Nyitray noted, the prevalence of cancer in the anal canal is much higher than was reported in the Amsterdam and Sao Paulo studies, even though subjects in these studies were from seemingly high-risk groups. “This prevalence wouldn’t be surprising for men who have sex with men but for heterosexual men it was unexpected,” Nyitray said.

Roughly one third of the men with anal HPV infection harbored a type that can cause cancer, the report indicates.

“There are a number of questions this study raises,” Nyitray said. “For instance, how was HPV transmitted to the perianal region and anal canal of these men” and “how persistent are the infections,” which are likely to affect the risk of anal cancer.

SOURCE: Journal of Infectious Disease, June 15, 2008.