Hepatitis E Virus in Sperm

Hepatitis E Virus is one of the leading causes of the acute viral liver infection in humans worldwide, mostly in developing regions where sanitation is poor. The virus is also endemic in pigs in the United States – though it is present mostly in organs rather than muscle, and is killed when the meat is cooked.

Because Hepatitis E Virus has been linked to fatal pregnancy complications and reports of male infertility in the developing world, researchers explored its infectivity in pigs, whose reproductive anatomy closely resembles that of humans[1].

After inoculating pigs with Hepatitis E Virus, the team found the virus circulated in blood and was shed in feces, meaning that the pigs were infected, but they had no clinical symptoms. Asymptomatic cases are also common in humans. Results also showed Hepatitis E Virus was present on the head of sperm cells, and that these same viral particles could infect human liver cells in culture and begin replicating.

Sexually transmitted organisms are those able to find safe haven in testicles, where they are protected by a blood-testis barrier that immune cells cannot cross. In addition to pregnancy and reproductive disorders linked to Hepatitis E Virus, there are signs it can also lead to pancreatic and neurological disorders in humans. Historically, clinical infections – even in pregnant people – have been assumed to be traced to fecal-oral transmission.

Using fluorescence microscopy in this new study to examine pig semen 84 days after inoculation with Hepatitis E Virus, the authors detected viral particles associated with at least 19% of sperm cells collected from the infected swine.

The study also showed that Hepatitis E Virus’ presence correlated with damaged sperm – potentially altering their structure and decreasing their ability to move through seminal fluid. That said, the researchers can’t yet say that these changes directly translate into fertility problems, though the link between an Hepatitis E Virus infection and human infertility suggests this could be the case.

There are implications for the swine industry, as well. Most commercial pig litters are produced by artificial insemination, with donor sperm distributed broadly from large breeder facilities.

[1] Yadav et al: Infectious hepatitis E virus is associated with the mature sperm head. In PLoS Pathogens – 2024. See here.