- Zika virus infection is known to cause congenital brain abnormalities including microcephaly, if infection occurs during pregnancy.
- New study in mice indicates that Zika virus may also affect the male reproductive system, lowering testosterone levels and decreasing fertility.
- Virus might similarly affect men's ability to have children, though further research is needed to confirm the hypothesis.
- Low testosterone levels can be detected by a simple blood test, done a few weeks after Zika virus infection.
What the Study Hoped to EstablishThe authors of the study wanted to explore the effects of Zika virus infection on the male reproductive system.
‘Reduced testosterone levels following Zika virus infection may be diagnosed using a simple blood test.’
AdvertisementIt is known that the virus remains in the semen for months after infection. In fact, the Center for Disease Control and Prevention has recommended that persons who travel to Zika endemic areas use condoms for at least six months, irrespective of whether they had symptoms of Zika virus infection.
However, it is not known what long term effects the virus may have on the male reproductive system (testes).
Details of the Study
To determine the effects of Zika virus infection on the testes, the researchers injected male mice with the Zika virus and they noticed the following changes
- Within a week, the virus had reached the testes, which then showed signs of inflammation on microscopic examination.
- By two weeks, both the testes were noticeably smaller, their internal framework was collapsing, and many cells were dead or in the process of dying.
- When the testes were examined after three weeks, they had shrunk to one-tenth of their original size and the internal structure had completely collapsed. Additionally, their sex hormone were low, and their sperm continued to stay infected.
- The mice were watched for six weeks, and during that time the testes showed no signs of healing or repair, even though the mice had cleared the virus from their bloodstream.
The internal framework of the testes is maintained by Sertoli cells, which nourish the developing sperm, and these cells also keep the blood-testes barrier intact. In Zika virus infection, scientists found that Sertoli cells were destroyed, and Sertoli cells are not capable of regeneration.
Effect of Zika Virus Infection on The Fertility of Male MiceTo test the effect of Zika virus infection on the fertility of male mice, healthy female mice were mated with infected and uninfected male mice. It was found that females paired with infected male mice were about four times less likely to become pregnant compared to those paired with uninfected males.
"This is the only virus I know of that causes such severe symptoms of infertility," said Moley, a fertility specialist and director of the university's Center for Reproductive Health Sciences. "There are very few microbes that can cross the barrier that separates the testes from the bloodstream to infect the testes directly."
Does Zika Virus Affect Men Too?Until now, no reports have been published that link Zika virus infection to male infertility, but the study authors feel that infertility is difficult to detect in epidemiological surveys.
According to one of the study authors, "People often don't find out that they're infertile until they try to have children, and that could be years or decades after infection," Moley said. "I think it is more likely doctors will start seeing men with symptoms of low testosterone, and they will work backward to make the connection to Zika."
Effects of Testicular Damage and Low Testosterone Levels
Testosterone is the most important androgenic hormone. Androgens are male reproductive hormones that begin to increase at puberty and are responsible for development of male features such as muscle, facial and body hair, and deepening of voice. In addition, testosterone also influences male sex drive (libido), and stimulates testes to produce sperm, contributing to fertility. It is mainly produced in the testes.
Damage to testes by infection or cancer lowers testosterone levels. Men with low testosterone consequently suffer from a low sex drive, erectile dysfunction, tiredness and loss of body hair and muscle mass. Since sperm production by the testes is also affected, these men can also have low levels of fertility.
Low testosterone levels can be diagnosed by a simple blood test. Following Zika virus infection, serum testosterone levels may be measured to determine if they are lowered.
Further Studies Needed to Determine How Zika Virus Affects Men
This study revealed that Zika virus infection reduces fertility of male mice. However, further research is needed to determine if men are also similarly affected. The scientists feel that studies have to be undertaken in regions having high rates of Zika virus infection to learn how it affects male reproductive health.
"Now that we know what can happen in a mouse, the question is, what happens in men and at what frequency?" Diamond said. "We don't know what proportion of infected men get persistently infected, or whether shorter-term infections also can have consequences for sperm count and fertility. These are things we need to know."
- Androgen Deficiency - (https:www.andrologyaustralia.org/your-health/testosterone/)