A new study conducted by researchers at Ohio State University has uncovered that the hepatitis E virus (HEV), found associated with sperm in pigs, might indicate that the virus could be transmitted sexually and may be linked to male infertility. HEV is primarily recognized as the leading cause of acute viral liver infections in humans globally, particularly prevalent in regions with poor sanitation. Interestingly, in the United States, the virus is endemic among pigs, residing primarily in organs rather than muscle tissue, and can be eliminated by cooking the meat thoroughly.
Given the associations between HEV and severe complications during pregnancy, as well as instances of male infertility in less developed areas, the research team explored the virus’s behaviour in pigs due to their reproductive anatomy’s resemblance to that of humans. After introducing HEV to pigs, the study observed that the virus circulated in the bloodstream and was excreted in faeces, suggesting that the pigs were infected but exhibited no clinical symptoms. This condition is often asymptomatic in humans as well. Crucially, the researchers discovered HEV on the heads of sperm cells, which could infect and replicate within human liver cells in laboratory settings.
Kush Yadav, the study’s lead author and a PhD student at Ohio State’s Center for Food Animal Health, highlighted the significance of their findings, stating, “This is the first study to demonstrate an association of the hepatitis E virus with sperm cells. Our future research will focus on understanding this relationship more deeply and determining through further animal model studies whether sexual transmission of the virus occurs, as its presence in human settings remains uncertain.” This groundbreaking research was recently published in the journal PLOS Pathogens, shedding light on a potentially new route of HEV transmission.
Sexually transmitted organisms, including HEV, can find a protective environment in the testicles, shielded by a blood-testis barrier that immune cells cannot breach. In addition to reproductive disorders, HEV is also suspected to cause pancreatic and neurological disorders in humans. Historically, HEV infections, even among pregnant individuals, were thought to be solely due to fecal-oral transmission routes.
The study also employed fluorescence microscopy to investigate pig semen 84 days after HEV inoculation, where Yadav detected viral particles on approximately 19% of the sperm cells collected from the infected pigs. He noted, “It’s unclear whether the viruses are on the outside or inside of the sperm cells or if hepatitis E can complete a replication cycle in the sperm head, so it appears sperm may be more of a carrier rather than a susceptible cell.” This discovery also showed a correlation between the presence of HEV and sperm damage, which could alter their structural integrity and decrease their motility, potentially leading to fertility issues.
Scott Kenney, an associate professor of veterinary preventive medicine and Yadav’s supervisor, emphasized the broader implications of their findings, suggesting that “Between 20 and 50% of male infertility cases remain unexplained. Hence, we are advocating for more extensive screening for the hepatitis E virus as a potential cause for these cases.” Additionally, the results of this study suggest that sexual partners of pregnant women who test positive for HEV should also be screened. However, the evidence for sexual transmission in humans has yet to be established conclusively.
Moreover, these findings have significant implications for the swine industry, where most pig litters are produced through artificial insemination, and donor sperm is distributed widely from extensive breeding facilities. Kenney remarked, “This could be part of the problem with HEV being endemic across the country and raises questions about whether it causes a reduction in the reproductive capacity of the pigs. While HEV doesn’t cause enough damage to pigs to limit production profitability, if we could implement some cost-effective screening or vaccination at these upstream boar facilities, maybe we could reduce the introduction of the virus into new herds.” This research opens new avenues for understanding HEV transmission and its broader impact on human and animal health.
More information: Kush K. Yadav et al, Infectious hepatitis E virus is associated with the mature sperm head, PLoS Pathogens. DOI: 10.1371/journal.ppat.1012240
Journal information: PLoS Pathogens Provided by Ohio State University
