Another danger of the Zika virus
Zika virus reduces male fertility (in mice)
Julia Korowski, XX2 century, based on EurekAlert! (Zika infection causes reduced fertility, low testosterone in male mice)
Most studies of the Zika virus are devoted to how it affects the health of pregnant women and fetal development. Scientists from Washington University in St. Louis have demonstrated that Zika can be no less dangerous for men.
They injected the virus into male mice, and after three weeks, the testicles of the animals decreased in size, the level of sex hormones fell, and the ability to conceive decreased. The results of the scientific work are published in the journal Nature (Govero et al., Zika virus infection damages the tests in mice – VM).
"We conducted this study to understand how Zika virus infection affects males," says one of the authors, Professor Michael Diamond. "Although we have conducted experiments on mice – I will make a reservation that we do not yet know whether Zika has the same effect on humans – the results suggest that infected men may have lower testosterone levels and sperm counts, which, in turn, will affect fertility."
Zika virus in mouse semen
It is known that the virus persists in semen for several months. The US Centers for Disease Control and Prevention recommends that men who have visited regions where the Zika epidemic is raging use condoms for six months, regardless of whether, even if they do not show symptoms of the disease. However, it is not yet known how a prolonged infection affects the reproductive system of men.
To find out, the researchers infected male mice with Zika. A week later, the virus moved into the testes, after three testicles decreased to one tenth of the normal size, and their internal structure was completely destroyed. The animals were observed for six weeks, during which time their reproductive system did not recover.
The sad picture persisted even when the virus was no longer detected in the blood. "We don't know for sure if the damage is reversible, but I believe it's not, because the cells that supported the internal structure were infected and destroyed by the virus," says Diamond.
The structure of the testes depends on Sertoli cells, they maintain a physical barrier between blood vessels and seminal tubules and nourish future spermatozoa. The researchers found out that the Zika virus infects and kills these cells, and subsequently they do not regenerate. Testicles produce not only sperm, but also testosterone, and six weeks after infection with the Zika virus, the hormone level in mice decreased significantly, and the number of motile sperm decreased tenfold.
Healthy females who mated with infected males became pregnant four times less often. "This is the only virus I know that causes such serious infertility symptoms," says Kelle Moley, a member of the scientific group. "There are very few microorganisms that are able to cross the barrier separating the testes from the bloodstream and infect the testicles directly." At the moment, there are no published works linking the virus with male infertility, but scientists believe that this is due to the fact that infertility is difficult to detect during an epidemiological survey. "People often do not know that they are infertile until they try to conceive a child, and this can happen years and decades after infection," explains Molly. "I think it's more likely that doctors will encounter men with low testosterone levels, start looking for causes and link them to the Zika virus."
In order to find out how the virus affects the reproductive system of men, it is necessary to conduct research in those regions where Zika is common. "Now that we know what can happen to mice, the question is what and how often happens to men," Diamond sums up. "We don't know what percentage of infected men face chronic infection and whether a short–term infection can affect the number of sperm and the ability to conceive."
Zika virus is a type of virus of the genus Flavivirus, carried by mosquitoes of the genus Aedes. There have also been suggestions about the possibility of sexual transmission of the virus from person to person. In humans, it causes a disease of the same name with characteristic symptoms in the form of rash, fatigue, headache and joint pain, fever, swelling of the joints. It was discovered in 1947, after which only 15 cases of the disease were described in Black Africa and Southeast Asia for 60 years. Currently it has the status of a pandemic. It has gained a special distribution in Latin America and is gradually moving north. Cases of the disease have been reported in Miami and Florida. It has severe teratogenic side effects in the form of microcephaly and other defects of the brain and skull in infants born to mothers who have had the disease. There are no specific drugs or vaccines against the Zika virus today.
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