Study suggests hepatitis E can be sexually transmitted

Researchers have found that hepatitis E virus (HEV) is associated with sperm in pigs, suggesting that it may be sexually transmitted and linked to male infertility. The new discovery was published in the journal PLOS Pathogens.

Hepatitis E is the leading cause of acute viral liver infection in humans worldwide, mostly in developing regions with poor sanitation. The virus is also endemic in pigs in the United States, although it is primarily present in organs rather than muscle and is killed by cooking the meat.

Because hepatitis E is associated with fatal pregnancy complications and reports of male infertility in developing countries, researchers at Ohio State University studied its infectivity in pigs, whose reproductive anatomy is similar to humans.

After infecting pigs with HEV, the team found that the virus was circulating in the blood and shed in faeces, meaning the pigs were infected but had no clinical symptoms — asymptomatic cases are also common in humans. The results also showed that HEV was present on the head of sperm, and these same viral particles could infect human liver cells in culture and begin replicating.

"Our study is the first to demonstrate an association of hepatitis E virus with sperm cells," said first author Kush Yadav, who conducted the work as part of his doctoral dissertation at the Ohio State Food Animal Health Center.

Future research will focus on understanding the mechanical link between the hepatitis E virus and the sperm head, as well as using animal models to test whether the virus can be sexually transmitted. This is still unknown in the human context.

Sexually transmitted organisms can take refuge in the testicles, where they are protected by a blood-testicular barrier that immune cells cannot cross. In addition to pregnancy and reproductive problems associated with HEV, there are indications that the virus can also cause pancreatic and neurological disorders in humans.

Yadav works in the lab of Scott Kenny, the study’s senior author and an associate professor of veterinary preventive medicine at Ohio State University. Kenny studies HEV and other viruses in animals, particularly those that can infect people.

Using fluorescence microscopy to examine pig semen 84 days after HEV infection, Yadav found viral particles associated with at least 19% of sperm collected from infected pigs.

"We can't say whether they're on the outside or the inside of the sperm," he said. "We don't know whether the hepatitis E virus can complete its replication cycle in the head of the sperm, so we think the sperm is more of a carrier than a susceptible cell."

The study also found that the presence of HEV is associated with damaged sperm, potentially altering their structure and reducing their ability to move through seminal fluid. However, the researchers cannot yet say that these changes directly lead to fertility problems, although the link between HEV infection and male infertility points to this possibility.

Yadav suggested testing the sexual partners of pregnant women who test positive for HEV, although scientists have not yet established whether the virus can be transmitted sexually.

There are also implications for the pig industry, as most commercial piglets are produced by artificial insemination, with donor semen distributed from large breeding farms.

"This may be part of the problem with HEV endemicity across the country and raises the question of whether it reduces the reproductive capacity of pigs," Kenny said.

"Because HEV doesn't cause enough damage to pigs to limit profitability of production, I don't see the swine industry mass vaccinating against hepatitis E virus, but if we can implement some cost-effective screening or vaccination on these breeding farms, perhaps we can reduce the introduction of the virus into new herds."