Sex with animals – though the subject of jokes for millennia – is no laughing matter, not just on the basis of the cruelty involved, but also the health consequences, as a new Brazilian study shows.
The study of 492 rural Brazilian men found that 35 percent of study participants, who ranged from 18 to 80 years old and included both penile cancer patients and healthy men, reported having sex with animals in their lifetimes. A team of urologists from around the country co-authored the paper, perhaps the first such large study of its kind. The study focused specifically on risk factors related to penile cancer and found four, in order of importance: bestiality, smoking, the presence of premalignant tumors on the penis, and phimosis, which is the foreskin’s inability to retract over the penis.
Men who engaged in bestiality also reported a higher incidence of sexually transmitted disease, though it is unclear whether this was due to a higher rate of promiscuity among said men, or whether it was the consequence of group sex associated with bestiality (i.e., many men copulating with an animal on a specific occasion).
Forty five percent of the 118 men with penile cancer said they had engaged with sex with animals, in comparison to 32 percent of healthy men. The majority (59%) reported engaging in the act for one to five years, while a robust 21% said they had been doing it for more than five. The frequency of the sex acts ranged from monthly to daily.
It does not appear to matter whether the men engaged with more than one species of animal: the researchers found no association between penile cancer and the number of animals the men used over time. The species involved included mares, cows, pigs and chickens (!).
Hypothesizing about the causal relationship between bestiality and penile cancer, the researchers said that micro-injuries to the penis are probably involved in the development of penile cancer. Sex with animals tends to lead to physical trauma and injured tissue, since animals and humans are not exactly anatomically compatible. “The genital mucus membranes of animals could have different characteristics from human genitalia, and the animals’ secretions are probably different from human fluids. Perhaps animal tissues are less soft than ours, and non-human secretions would be toxic for us,” said lead author Stênio de Cássio Zequi, a urologist in São Paulo.
“The vagina in humans has moisturizing properties, which prevent penile injury. With animals, you’re at higher risk for micro-trauma, like cuts and scratches. And then whatever pathogens are there, like bacteria and viruses, are more likely to cause a problem,” said Tobias Köhler, a urologist at Southern Illinois University School of Medicine who was not involved in the research. He added that the study was rigorous and an important contribution to the field. “It adds to our knowledge of cancer prevention and gives us epidemiological data we never really had before on sex with animals.”
Zequi theorizes that micro-lesions caused by this toxicity could facilitate the action of some yet unrecognized microorganism during contact between different animal species.
As unbelievable as it may seem, bestiality is a practice with a long history and a record reaching back to antiquity. “In some antique civilizations there were temples or rituals designated for [bestiality] practices,” said Zequi, adding that scientific literature about sex with animals is very underrepresented, an unfortunate fact given that it continues to be practiced widely among poor, generally illiterate and isolated populations predominantly in the developing world. Penile cancer accounts for up to 10 percent of cancers in men in Asia, Africa and South America, although it is rare in the U.S. and Europe. Interestingly, sex with animals in the developed world, when it occurs, tends to be associated with the educated classes. The case of Dr. Kimberley Lindsay, Deputy Director for the Laboratory Science Policy and Practice Program Office at the CDC, comes to mind as a recent case covered by the media, in which the scientist was accused of performing lewd acts on pets.
Circumcision also plays a role in the development of penile cancer in those who perform sexual acts on animals. In populations where the foreskin is typically removed soon after birth, the rates of penile malignancies are almost nonexistent. Uncircumcised men may develop more micro-traumas during sex, according to one theory on why circumcision protects against cancer. Smegma, the white secretion that collects around the glans of the penis in uncircumcised men, is composed of fatty acids that have been shown to be highly carcinogenic, and could also help to explain the increased risk.