Men who have sex with animals may have an increased risk of penile cancer, a study finds.

A recent case-control study published in the peer-reviewed Journal of Sexual Medicine focused on men who lived in rural areas of Brazil.

Researchers compared the health and sex habits of 118 penile cancer patients to 374 healthy men who served as the control group. Among all the study participants 34.8% reported having sex with animals. More men in the cancer group reported having sex with animals than the controls, 44.9% versus 31.6%. Penile cancer is cancer of the tissue of the penis.

As for the why sex with animals may increase the risk of penile cancer, researchers theorize that it may cause microtrauma to penile tissue, which could come in contact animal secretions that are potentially harmful to humans. The association between having sex with animals and penile cancer may also be indicative of lifestyle choices, since those who had sex with animals also had more sex with prostitutes, more sexual partners and more sexually transmitted diseases than those who didn’t.


Since the study participants grew up in rural areas, they had access to animals. The average age of first contact with an animal was 13.5, and the average age of last contact was 17.1. Since sex with animals stopped around the same time the men started having sex with humans, researchers said these episodes wouldn’t necessarily constitute full-on zoophilia. Zoophilia entails not just having sex with animals, but also being sexually attracted to them and developing fantasies and obsessive urges about them as well.

Most men in the study -- 62% -- had sex with several animals and 38% used the same animal. Frequency and length of time varied: 14% had sex one time, while 39.5% had it weekly or more and 15% had in monthly. For about 80% of the study subjects the episodes lasted anywhere from a year to 26 years, but the average time was about four years.

As for the kinds of animals the men had sex with, mares were the most common, followed by donkeys, mules, goats, chickens, calves, cows, dogs, sheep and pigs.