London School of Hygiene & Tropical Medicine

Male mice infected with a mouse-adapted strain of Zika virus can experience tissue injury associated with decreased testis size, according to a new research published in Nature.

The study, conducted by the Washington University School of Medicine, also found the infected mice may have reduced levels of two sex hormones and sperm cells in the seminal fluid.

In addition to transmission by mosquitoes, Zika virus can be detected in the seminal fluid of affected males for extended periods of time and transmitted sexually. It has previously been shown that infecting male adult mice with the virus results in infection of the testes.

So what can we learn from this new research?  Philippe Mayaud, Professor of Infectious Diseases & Reproductive Health at the London School of Hygiene & Tropical Medicine, said:

"This is an important study. Although the experiments were conducted in mice, the findings warrant further investigation as this model is a good substitute for human biology. There are precedents of animal models showing direct effect on fertility of other Arboviral infections. This has potential ramifications for testes development of human males born with Congenital Zika Syndrome.

 "The effect of the Zika virus on male sexual health has largely been ignored due to the devastating effects it can have on newborn children. However, it is clearly an area of concern. Previous research has shown that a small proportion of men with Zika virus who have infected their female partners sexually have experienced serious genital problems, such as blood in their sperm or testes inflammation. Although cases are likely to be very rare, we cannot rule out the possibility that Zika virus may cause male infertility or subfertility.

"Understandably, the focus of current Zika virus research centres on issues such as establishing the level of risk for mothers and babies infected with the virus and its potential global. This study supports the need for more research on the potential life-changing impact for men who contract Zika virus."

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