State of Ohio

09/25/2024 | Press release | Distributed by Public on 09/25/2024 11:09

Pigs may be transmission route of rat hepatitis E to humans Study shows viral strain infects, circulates among swine

Researchers found that a strain of rat hepatitis E isolated from humans could infect pigs and was transmitted among co-housed animals in farm-like conditions.
Photo: Getty Images
25
September
2024
|
13:00 PM
America/New_York

Pigs may be transmission route of rat hepatitis E to humans

Study shows viral strain infects, circulates among swine

New research suggests that pigs may function as a transmission vehicle for a strain of the hepatitis E virus (HEV) common in rats that has recently been found to infect humans.

The Rocahepevirus ratti strain is called "rat HEV" because rats are the primary reservoir of the virus. Since the first human case was reported in a person with a suppressed immune system in Hong Kong in 2018, at least 20 total human cases have been reported - including in people with normal immune function.

People infected with rat HEV did not report exposure to rats, leaving the cause of infection undefined. The suspected cause during other human HEV infections, in many cases, is consumption of raw pork - making it a potential route for rat HEV as well.

Researchers at The Ohio State University found that a strain of rat HEV isolated from humans could infect pigs and was transmitted among co-housed animals in farm-like conditions. Rats are common pests in swine barns - suggesting that the pork production industry may be a setting in which rat HEV could make its way to humans.

"We always want to know which viruses might be up and coming, so we need to know the genetics behind this virus in the unlikely event something happens in the United States that would enable rat HEV to expand," said senior author Scott Kenney, an associate professor of veterinary preventive medicine at Ohio State based in the Center for Food Animal Health at the College of Food, Agricultural, and Environmental Sciences' Wooster campus.

The study was published recently in PNAS Nexus.

Hepatitis E is the leading cause 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 liver rather than muscle, and is killed when the meat is cooked.

Past studies testing the cross-species infectiousness of rat HEV showed the strain used in experiments did not infect non-human primates.

"It dropped off the radar for six or seven years because it was thought not to be a human pathogen. And now it's infecting humans, so we need to figure out why," Kenney said.

One strain linked to human disease is known as LCK-3110. First author Kush Yadav, who completed this work as a PhD student in the Center for Food Animal Health, used the viral genomic sequence to construct an infectious clone of LCK-3110.

The team first showed the cloned virus could replicate in multiple types of human and mammal cell cultures and in pigs. Researchers then injected pigs with an infectious solution containing the LCK-3110 strain or another HEV strain present in pigs in the U.S., as well as saline as a control condition.

Viral particles in the blood and feces were detected one week later in both groups receiving HEV strains, but levels were higher in pigs infected with rat HEV. Two weeks later, co-housed pigs that received no inoculations also began to shed rat HEV virus in their feces - an indication the virus had spread through the fecal-oral route.

Though infected pigs' organs and bodily fluids were also positive for viral RNA, the animals did not show signs of feeling sick. Previous research suggests rats don't have clinical symptoms, either.

Even so, the rat HEV virus was detected in cerebrospinal fluid of infected pigs - a finding that aligns with growing concern that various strains of HEV that infect humans can harm the brain. One human death linked to rat HEV was caused by meningoencephalitis.

"HEV is gaining importance for neurological disorders, and a lot of the research now points toward how neuropathology is caused by the hepatitis E virus," Yadav said. "And even though we have a small number of known human cases, a high percentage of them are immunosuppressed. That means transplant recipients in the United States could be at risk of infection by general HEV as well as rat HEV.

"Research could now focus on whether pork liver products contain rat HEV and explore food safety procedures to block the disease."

Yadav is now a postdoctoral researcher in the Virginia-Maryland College of Veterinary Medicine at Virginia Tech. Co-authors of the study, all from Ohio State, were Patricia Boley, Carolyn Lee, Saroj Khatiwada, Kwonil Jung, Thamonpan Laocharoensuk, Jake Hofstetter, Ronna Wood and Juliette Hanson.

Share this

Pigs may be transmission route of rat hepatitis E to humans
Share on: Twitter Share on: Facebook Share on: LinkedIn

More Ohio State News

24
,
| 08:00 AMAmerica/New_York

Coral reefs will continue to experience severe heat stress as rising temperatures cause the oceans to become unbearably hot - but a new study shows that altering their feeding habits could allow local populations to avoid total extinction.

Research into two species of coral native to Hawaii revealed that warmer waters caused by climate change play an important role in coral bleaching - a process that causes coral to lose their color - significantly disrupting coral health and growth. The effect that ocean acidification, a process that causes seawater to become more acidic due to the excess amount of carbon dioxide it has absorbed, has on heat-stressed coral was also investigated.

Over the last decade, there has been a rise in the incidence and severity of mass coral bleaching eventsaround the globe, leading to increased mortality for these vital organisms.

However, this work suggests that some coral may well be resilient to these extreme environmental changes, said Kerri Dobson, lead author of the study who completed the work as a graduate student in earth sciences at the Ohio State University.

"Each coral species responds differently to stress and employs different methods to recover from that stress," said Dobson, who currently teaches marine biology at the University of Southampton in the U.K. "Now we know that those responses depend on several factors."

According to the study, which was recently published in Nature Communications Earth & Environment, one of the most telling influences that can decide if coral might recover from a stressful event is its access to food.

Typically, corals feed by receiving nutrition provided by photosynthetic symbiotic algae and catching and eating tiny aquatic organisms called zooplankton. These algae also give coral their vibrant color, but when heat stressed, corals lose their algae, leaving them bleached white and starving.

In this work, researchers collected branch samples from bleached and non-bleached parent colonies following one large-scale heat-stress event in 2014 as well as a second, unexpected, heat-stress event in 2015. Once rehoused in special tanks, half of the corals were subjected to a different amount of food and simulated ocean acidification rates to see how these factors affected their potential recovery.

"This is one of the first studies, to our knowledge, that has been able to capture the impact of natural thermal stress on coral in two consecutive years," Dobson said.

As a result of such unique long-term data, the team found that feeding coral zooplankton after a bleaching event could improve their overall resilience to warming temperatures, essentially minimizing mortality, promoting growth and enhancing coral recovery rates.

Ocean acidification did little to slow the corals' recovery, suggesting that some corals could survive in more acidic waters. Unfortunately, this discovery also makes clear that the most present danger to coral reefs is heat stress, said Dobson.

"Heat stress affected the corals' health much more than the simulated ocean acidification," she said. "These heat-stress events function as selection forces, leaving only the more thermally tolerant coral that might be able to survive the stresses that we're subjecting them to."

Finally, the study's findings emphasize the importance of understanding the conditions and evolutionary strategies that contribute to long-term coral survivorship, said Dobson. Moreover, this research offers a path for scientists and watch groups to better customize management and restoration efforts for coral reefs based on their species and location.

"This paper adds to our body of knowledge about coral resilience," said Andrea Grottoli, senior author of the study and a professor in earth sciences at Ohio State. "It gives us more leverage in following up on evaluating how we can protect corals and manage bleaching events by manipulating the environment to their favor."

While predictions about coral survivorship in the face of human-induced climate change do make room for hope concerning the fate of corals, these assumptions are based on the adherence to current climate mitigation goals, said Grottoli.

For example, it is possible that corals could adapt enough to survive a 2 degree Celsiusincrease in global temperatures. However, Earth's current unmitigated acceleration to 4 degrees of warming by the end of the century could eradicate coral completely, she said.

As the next few decades are critical to determining the reality of these scenarios, Dobson's future work will continue to investigate the impact of thermal stress on the ecology of coral reefs in other regions.

"When you do experiments with living animals in a natural setting, there's always some degree of unpredictability, as we saw with the unexpected second heat-stress event we studied," said Grottoli. "Ultimately, you have to roll with it because the work matters, and sometimes the things you didn't plan to learn are the parts that are the most interesting."

This research was supported by the National Science Foundation. Other co-authors include Jeremy C. Williams and Rowan H. McLachlan from Ohio State and Christopher P. Jury and Robert J. Toonen from the University of Hawai'i.

Show previous itemsShow next items