Zika Virus Reduces Fertility in Male Mice: Does This Translate to Humans?

Much of the research on the effects of Zika virus has focused on women’s health issues—and rightfully so, given the pregnancy-related complications (congenital microcephaly among other complications complications) that have been associated with the mosquito-borne virus.

Now, new research suggests that the virus that has plagued Brazil and parts of the Caribbean, as well as south Florida, may also affect male sexual health. In a study published online by the journal Nature on October 31^st, researchers used a mouse-adapted form of the African Zika virus strain Dakar 41519 to assess what, if any, consequences infection may have on the male reproductive tract. It has been well-documented that Zika can be detected in the seminal fluid of affected males for extended periods, and transmitted sexually during that time.

During their experiments, the authors of the Nature study—from Washington University School of Medicine in St. Louis—found that Zika persisted in the “testis and epididymis” of male mice, resulting in a 90% reduction in testicle weight. They also noted that this led to tissue injury causing “diminished testosterone and inhibin B levels, and oligospermia,” or low fertility, with sperm output reductions of up to 75%. In all, infected mice were successfully able to impregnate females at approximately one fourth of the normal rate in healthy mice, and the number of fetuses in pregnant females was reduced by more than 50%.

According to the authors, Zika virus also “preferentially infected spermatogonia, primary spermatocytes, and Sertoli cells” in the testes. This caused cell death and seminiferous tubule destruction in the experimental mice. Importantly, they also found that an Asian strain of Zika, H/PF/2013, caused less damage, but that this may be due to the fact that this strain replicates less efficiently in mice.

Although the authors were quick to emphasize that these findings in mice don’t necessarily translate into men, they do believe that further studies of sperm function and viability in male Zika patients is warranted. “We just don't know that yet,” study co-author Michael Diamond, PhD, professor of molecular microbiology at Washington University told ABC News about the true sexual health implications Zika has in men. Dr. Diamond did add, though, that he believes that the damage sustained by mice is permanent.

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.