Male fertility has been declining steadily for decades. Studies from the 1990s show that sperm counts and quality have dropped since the 1940s. More recent data reveals that rates of male infertility have surged by nearly 80% from 1990 to 2019.
Experts usually blame falling fertility on social and economic factors, like the high costs of raising children. But now, scientists warn that infections caused by parasites could also play a role.
One parasite, called Toxoplasma gondii, has come under scrutiny. It causes toxoplasmosis, an infection often considered harmless in healthy people. However, this parasite may directly harm sperm cells, affecting male fertility.
What is Toxoplasma gondii?
Toxoplasma gondii is a microscopic parasite found worldwide. It often lives in cats and can spread through their feces. People can also get infected by eating undercooked meat from animals like lamb, pork, or venison.
The parasite usually causes no symptoms or only mild flu-like signs in healthy individuals. But it can be dangerous for pregnant women, newborns, and people with weak immune systems.
Once a person is infected, the parasite can remain dormant in the body for life. It forms cysts in organs such as the brain, heart, and muscles. Sometimes, these cysts can reactivate and cause severe illness.
Parasite’s Link to Male Reproductive Health
New studies show that Toxoplasma gondii can reach the male reproductive system, including the testes and epididymis — where sperm mature and are stored.
Research published earlier this year revealed something alarming. When human sperm came into contact with the parasite in laboratory conditions, many sperm cells lost their heads within minutes. This “decapitation” of sperm was directly caused by the parasite.
Further observations showed that even the sperm cells that kept their heads were often misshapen or damaged. Scientists believe the parasite tries to invade sperm cells like other body cells, which may explain the damage.
What This Means for Male Fertility
Experts are cautious about jumping to conclusions. While animal studies strongly support that Toxoplasma gondii invades male reproductive organs, it is still unclear how much harm it causes in humans.
Cases of testicular toxoplasmosis, where the parasite infects the testes, are rare and mostly found in people with weakened immune systems. There is little evidence so far that it commonly causes symptoms in otherwise healthy men.
Some studies suggest that men infected with toxoplasmosis show sperm abnormalities, but the sample sizes are too small to confirm a clear link. Also, the parasite’s infection rates have not risen in high-income countries even as infertility has increased. This suggests that toxoplasmosis may be only one piece of a larger fertility puzzle.
How Do People Get Infected?
Toxoplasma gondii spreads through several routes. Eating raw or undercooked meat contaminated with the parasite is a major source. Unwashed fruits and vegetables exposed to cat feces or contaminated soil can also carry the parasite.
People can become infected by handling cat litter boxes or gardening without proper hygiene, as contact with infected cat feces is a common way to contract toxoplasmosis.
What Can Be Done?
Scientists emphasize the importance of preventing this infection. Since it affects up to half of the global population, reducing exposure could help protect overall health, including reproductive health.
Good food safety practices — like thoroughly cooking meat and washing fruits and vegetables — are essential. Proper hygiene when cleaning cat litter boxes and avoiding contact with contaminated soil can also reduce risk.
Conclusion
The discovery that Toxoplasma gondii may directly damage sperm is a major step in understanding male infertility. However, more research is needed to fully determine its impact on human fertility.
While toxoplasmosis is unlikely to be the sole cause of the worldwide decline in male fertility, it highlights the need to consider infections as one of many factors affecting reproductive health.
Preventing exposure to this common parasite remains an important public health goal, especially for those planning to start families.
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