causes infertility, lasting harm to testes in mice: U.S.
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[November 01, 2016]
By Julie Steenhuysen
CHICAGO (Reuters) - A study of mice
infected with Zika showed the virus caused lasting damage to key cells
in the male reproductive system, resulting in shrunken testicles, lower
levels of sex hormones and reduced fertility, U.S. researchers said on
So far, the findings are only in mice, but the result is worrisome
enough to warrant further study because of possible implications for
people, said Dr. Michael Diamond of Washington University in St.
Louis, whose research was published in the journal Nature.
"It has to be corroborated," Diamond, a professor of pathology,
immunology and molecular microbiology, said in a telephone
Much of the global effort to fight Zika has focused on protecting
pregnant women from infection because of the grave implications for
their unborn children.
Zika infections in pregnant women have been shown to cause
microcephaly, a severe birth defect in which the head and brain are
undersized, as well as other brain abnormalities.
Previous studies have shown that Zika can remain in semen for as
long as six months. But little is known about whether prolonged
exposure to the virus in the testes can cause harm.
To study this, Diamond and colleagues injected male mice with Zika.
After a week, the researchers recovered infectious virus from the
testes and sperm, and they found evidence of viral genes in certain
cells of the testes. But overall, the testes appeared normal
compared with other lab mice.
After three weeks, however, the differences were stark. The testes
in the Zika-infected mice had shrunk to a tenth of their normal
size, and the internal structure was destroyed.
"We saw significant evidence of destruction of the seminiferous
tubules, which are important for generating new sperm," Diamond
The researchers also found that Zika infects and kills Sertoli
cells, which maintain the barrier between the bloodstream and the
testes and foster sperm growth. Sertoli cells do not regenerate.
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That raises the specter of long-lasting damage.
"The virus is infecting a site which doesn't really renew if it gets
damaged. That is the problem," Diamond said.
Tests of testicular function showed sperm counts, sex hormones and
fertility had dropped. Infected mice were four times less likely to
impregnate a healthy female mouse than healthy males.
"This is the only virus I know of that causes such severe symptoms
of infertility," added Dr. Kelle Moley, a fertility specialist at
Washington University and a study co-author.
There is no vaccine or treatment for Zika.
(Reporting by Julie Steenhuysen; Editing by Will Dunham)
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