Male fertility charges had been plummeting over the last half-century. An research from 1992 famous a gentle lower in sperm counts and high quality because the Nineteen Forties. A more moderen find out about discovered that male infertility charges larger just about 80% from 1990 to 2019. The explanations using this development stay a thriller, however often cited culprits come with weight problems, deficient nutrition and environmental toxins.
Infectious illnesses similar to gonorrhea or chlamydia are incessantly lost sight of elements that have an effect on fertility in males. Collecting proof suggests {that a} not unusual single-celled parasite referred to as Toxoplasma gondii will also be a contributor: An April 2025 find out about confirmed for the primary time that “human sperm lose their heads upon direct contact” with the parasite.
I’m a microbiologist, and my lab research Toxoplasma. This new find out about bolsters rising findings that underscore the significance of forestalling this parasitic an infection.
The various tactics you’ll get toxoplasmosis
Inflamed cats defecate Toxoplasma eggs into the clutter field, lawn or different puts within the atmosphere the place they are able to be picked up via people or different animals. Water, shellfish and unwashed fruit and veggies too can harbor infectious parasite eggs.
Along with eggs, tissue cysts provide within the meat of warm-blooded animals can unfold toxoplasmosis as smartly if they don’t seem to be destroyed via cooking to correct temperature.
Whilst maximum hosts of the parasite can keep watch over the preliminary an infection with few if any signs, Toxoplasma stays within the frame for lifestyles as dormant cysts in mind, middle and muscle groups. Those cysts can reactivate and motive further episodes of critical sickness that injury important organ programs.
Between 30% and 50% of the arena’s inhabitants is completely contaminated with Toxoplasma because of the numerous tactics the parasite can unfold.
Toxoplasma can goal male reproductive organs
Upon an infection, Toxoplasma spreads to just about each and every organ and skeletal muscle. Proof that Toxoplasma too can goal human male reproductive organs first surfaced throughout the peak of the AIDS pandemic within the Nineteen Eighties, when some sufferers introduced with the parasitic an infection of their testes.
Whilst immunocompromised sufferers are maximum in peril for testicular toxoplasmosis, it may possibly additionally happen in in a different way wholesome folks. Imaging research of contaminated mice ascertain that Toxoplasma parasites briefly commute to the testes along with the mind and eyes inside of days of an infection.
Toxoplasma cysts floating in cat feces.
DPDx Symbol Library/CDC
In 2017, my colleagues and I discovered that Toxoplasma too can shape cysts in mouse prostates. Researchers have additionally noticed those parasites within the ejaculate of many animals, together with human semen, elevating the potential for sexual transmission.
Understanding that Toxoplasma can are living in male reproductive organs has caused analyses of fertility in contaminated males. A small 2021 find out about in Prague of 163 males contaminated with Toxoplasma discovered that over 86% had semen anomalies.
A 2002 find out about in China discovered that infertile {couples} are much more likely to have a Toxoplasma an infection than fertile {couples}, 34.83% as opposed to 12.11%. A 2005 find out about in China additionally discovered that sterile males are much more likely to check certain for Toxoplasma than fertile males.
Now not all research, alternatively, produce a hyperlink between toxoplasmosis and sperm high quality.
Toxoplasma can immediately injury human sperm
Toxoplasmosis in animals mirrors an infection in people, which permits researchers to handle questions that aren’t simple to inspect in folks.
Testicular serve as and sperm manufacturing are sharply decreased in Toxoplasma-infected mice, rats and rams. Inflamed mice have considerably decrease sperm counts and a better share of abnormally formed sperm.
In that April 2025 find out about, researchers from Germany, Uruguay and Chile noticed that Toxoplasma can succeed in the testes and epididymis, the tube the place sperm mature and are saved, two days after an infection in mice. This discovering caused the crew to check what occurs when the parasite comes into direct touch with human sperm in a check tube.
After most effective 5 mins of publicity to the parasite, 22.4% of sperm cells have been beheaded. The choice of decapitated sperm larger the longer they interacted with the parasites. Sperm cells that maintained their head have been incessantly twisted and misshapen. Some sperm cells had holes of their head, suggesting the parasites have been seeking to invade them as it could every other form of mobile within the organs it infiltrates.
Along with direct touch, Toxoplasma may additionally injury sperm for the reason that an infection promotes power irritation. Inflammatory stipulations within the male reproductive tract are damaging to sperm manufacturing and serve as.
The researchers speculate that the damaging results Toxoplasma will have on sperm may well be contributing to very large international declines in male fertility over the last many years.
Sperm uncovered to Toxoplasma. Arrows level to holes and different injury to the sperm; asterisks point out the place the parasite has burrowed. The 2 nonconfronted controls on the backside display commonplace sperm.
Rojas-Barón et al/The FEBS Magazine, CC BY-SA
Fighting toxoplasmosis
The proof that Toxoplasma can infiltrate male reproductive organs in animals is compelling, however whether or not this produces well being problems in folks stays unclear. Testicular toxoplasmosis presentations that parasites can invade human testes, however symptomatic illness may be very uncommon. Research up to now that display defects within the sperm of contaminated males are too small to attract company conclusions presently.
Moreover, some studies recommend that charges of toxoplasmosis in high-income international locations have now not been expanding over the last few many years whilst male infertility was once emerging, so it’s more likely to most effective be one a part of the puzzle.
Without reference to this parasite’s possible impact on fertility, it’s smart to steer clear of Toxoplasma. An an infection could cause miscarriage or delivery defects if anyone acquires it for the primary time throughout being pregnant, and it may be life-threatening for immunocompromised folks. Toxoplasma may be the main explanation for dying from foodborne sickness in the USA.
Taking correct care of your cat, promptly cleansing the clutter field and carefully washing your fingers after can assist cut back your publicity to Toxoplasma. You’ll additionally offer protection to your self from this parasite via washing fruit and veggies, cooking meat to correct temperatures sooner than eating and keeping off uncooked shellfish, uncooked water and uncooked milk.
