A new study from researchers at Tulane National Primate Research Center suggests the coronavirus may infect four different areas of the male genital tract, adding to evidence that a COVID-19 infection may impact male fertility.
The primate center, a 500-acre complex in Covington with a population of roughly 4,800 primates, found that the coronavirus infected the penis, prostate, testicles and a network of temperature-regulating veins in three male rhesus macaques.
When the study began, the scientists thought the coronavirus might be discovered in the gut, like other similar viruses. But that’s not what they found, said Ronald Veazey, a professor of pathology at the Tulane University School of Medicine and an author of the study.
“Surprisingly, the male reproductive tract lit up like a Christmas tree,” said Veazey. “We weren’t even thinking male – it just happened to be a male macaque.”
The study is a preprint and has not yet been peer-reviewed. It also doesn't address whether the effects on the male organs are long-term or whether the high viral load corresponds to symptoms like pain, erectile dysfunction or low sperm count. Still, it adds evidence to a growing number of reports linking COVID infection to male reproductive issues.
A number of studies have shown lower sperm counts in men of reproductive age with COVID-19, according to an analysis of medical literature published in the journal Urology in Jan. 2022. In a small study from researchers in Italy, men were almost six times more likely to report erectile dysfunction after COVID infection.
“The effect of the virus is not only on the respiratory system, but almost all organ systems – the GI tract, the nervous system and now there is more evidence it might go to the male genital tract,” said Dr. Yujiang Fang, a urologist, professor of pathology at Des Moines University and adjunct faculty in the urology division at University of Missouri.
But Fang, who was not involved in the primate study, also points out that this study is preliminary, and results from animal studies are not always replicated in humans. How much virus stays in a human’s genital tract may depend on their immune system and whether they are vaccinated.
Fang said some patients do report erectile dysfunction after a COVID infection, reflected in a growing body of research. But that could be due to another way the virus affected the organ, such as an inflammatory response or damage to the muscle, or other factors, such as stress.
Regardless, both the study authors and Fang said follow-up will be important to measure how the coronavirus impacts male fertility.
"This is going to open new doors to study the SARS-CoV-2 with male genital tract cells," said Fang.
The findings also highlight the growing contrast between what scientists have learned about COVID and the misinformation that's spread on social media and through other channels. There are widespread myths that COVID vaccines can cause infertility in women and impotence in men, which researchers have not found any evidence of. The Tulane study and others suggest, however, that there could be a risk of infertility from COVID infection.
The Tulane study took place a year and a half ago, as scientists were deepening their understanding of COVID-19 as more than just a respiratory disease and one that could affect the cardiovascular system.
Male reproductive organs have a large network of blood vessels and a high number of ACE2 enzymes, which the coronavirus uses to bind to cells. It made sense that that area would see a higher concentration of coronavirus, Veasey said.
“What tissue in the body would be the most responsive and have the most expansion and contraction? The penis,” said Veazey. “It’s a major target.”
A rhesus macaque monkey stares at a visitor from its cage at the Tulane National Primate Research Center near Covington in 2004.
Getting approval to work with the coronavirus and primates is a lengthy process, but the group was able to try the same thing with two other subjects. The process involved injecting the infected primates with an altered, fluorescent antibody that would bind to the virus, and then light up the most infected organs using a special imaging scan.
All three monkeys showed the same bright spots on the male organs, even as other infected areas, such as the lungs, started to resolve over two weeks.
While just three cases might sound small, testing of this nature in animals is much more controllable than in a human study, Veazey said. Scientists know exactly when they were infected and can use scans to easily look for reproductive issues rather than relying on people to self-report symptoms after incidental infection.
“Three out of three is pretty phenomenal,” said Veazey.
In order to better understand the issue, Veazey said people experiencing symptoms of erectile dysfunction should report it to their doctor. The researchers also urged vaccination, which limits the level of virus replication.
“It certainly is another excuse to get vaccinated,” said Veazey. “Any strong virile males who think the vaccines going to hurt them probably should reconsider.”
The Tulane Primate Center has conducted COVID research since the beginning of the pandemic as one of seven primate research facilities studying infectious diseases around the country. The facility has received $17.8 million to conduct COVID research thus far.
