Zika virus infection
- 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
may also affect fertility in men,
suggests a recent study done in mice.
What the Study Hoped to Establish
The 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.’
It 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
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
"We don't know for certain if the damage is
irreversible, but I expect so, because the cells that hold the internal
structure in place have been infected and destroyed,"
- 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
- 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.
said Diamond, who is also a professor of pathology and immunology, and
of molecular microbiology.
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
To 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
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
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
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
Damage to testes by infection or cancer lowers
. Men with low
testosterone consequently suffer from a low sex drive, erectile
, 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
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/)