A new study reveals that Toxoplasma gondii, a parasite tied to cats and infecting over 40 million Americans and 30-50% of the global population, may wreak havoc on male fertility by “colonizing” testes and damaging sperm.
The parasite is commonly linked to the “crazy cat lady” stereotype because it is found in cat feces—cats being its only known definitive hosts—and is associated with mental health issues like schizophrenia, bipolar disorder, obsessive-compulsive disorder, and suicidal behavior.
Researchers from Chile, Germany, and Uruguay, in a peer-reviewed study published in the FEBS Journal, found that the parasite’s rapidly dividing tachyzoites infiltrate testes and sperm-storing tubes, resulting in headless or mangled sperm. The study suggests T. gondii disrupts mitochondrial activity, causing oxidative stress that may contribute to male infertility. Studies on infected mice, rats, and rams show reduced sperm counts and abnormal sperm shapes, though human data remains limited.
The Centers for Disease Control and Prevention (CDC) notes that T. gondii spreads through undercooked meat, contaminated produce, cat excrement, or infected organ transplants. To reduce infection risk, the CDC recommends wearing gloves while gardening, cooking meat to safe temperatures, freezing meat before cooking, thoroughly washing vegetables, and changing cat litter daily.
As male fertility rates decline globally, this research raises concerns about the cat-linked parasite’s role, though further studies are needed to confirm its impact on humans.
The study referenced in the article, published in the FEBS Journal in April 2025, can be found here: Adverse impact of acute Toxoplasma gondii infection on human spermatozoa.