New study explores potential cross-species spread of chronic wasting disease
A new study suggests
chronic wasting disease (CWD) may be more unpredictable than previously
thought.
Source: University of Calgary
Summary: A new study found that chronic wasting disease can sometimes spread silently, with infectious prions present even in animals that show no symptoms. While there is no confirmed human risk, researchers say the disease’s ability to evolve and spread across species warrants close attention.
Infectious prions may
spread unnoticed, which raises new concerns as the fatal wildlife disease
continues to spread. Scientists have discovered a previously unknown aspect
of chronic wasting disease. AI/ScienceDaily.com is credited. Chronic wasting
disease (CWD) is best known as a disease affecting wildlife such as deer and
elk. However, a new study conducted by
University of Calgary researchers and international collaborators investigated
the possibility that the disease could spread to other species beyond
cervids—plant-eating hooved animals. CWD has never been confirmed in an
individual. Even so, scientists say the new findings highlight the importance
of continued monitoring and research as the disease continues to spread into
new areas.
CWD is a fatal
neurological disease caused by infectious proteins called prions. It is spreading more and more throughout
North America, including Alberta's expanding regions. Cross-Species
Transmission Potential Is Studied. In research published in Science Advances,
investigators used controlled laboratory experiments to study the zoonotic
potential of CWD. Most of the animals
involved did not develop symptoms.
However, researchers detected small amounts of infectious prions in
their tissues. When samples from those
animals were transferred to other species, the recipients developed signs of
CWD.
"These findings
show that even without obvious (clinical signs), infectious prions can still be
present and transmissible," says Dr.
Samia Hannaoui, PhD, researcher and assistant professor at the
University of Calgary Faculty of Veterinary Medicine (UCVM), and first author
on the study.
Why Prion Diseases
Are Difficult To Predict
Prions can change as
they move between hosts, which sets them apart from many other infectious
agents. This process may result in the development of new strains with distinct
characteristics over time. "We're not dealing with a single, fixed
agent," says Dr. Hermann Schaetzl,
MD, the study's final author and professor at the UCVM. "Strains of
prions can change, and that change can affect how the disease behaves."
According to the researchers, this ability to change makes prion diseases
especially challenging to forecast and manage.
CWD brings about yet
another issue. Animals infected with the disease can release infectious prions
into the environment long before symptoms become visible. Prions can be shed through urine and feces
for months or even years, contaminating vegetation and soil.
"By the time you
see clinical signs, the animal has often been infectious for a long time,"
says Schaetzl. "That's what makes
this disease particularly challenging to control."
The researchers
emphasize that their results do not point to an immediate threat to humans.
"Our findings
don't indicate an immediate risk to humans, but they do suggest the situation
is more nuanced than previously understood," says Schaetzl. "As CWD becomes more widespread,
understanding these dynamics becomes increasingly important."
Scientists also note
that prion diseases have crossed species barriers in the past. One well-known example is bovine spongiform
encephalopathy (BSE), commonly called "mad cow disease," which was
transmitted from cattle to humans.
Current evidence
indicates that a strong barrier exists between CWD and humans. However, the purpose of studies like this one
is to determine whether prions could gradually alter their spread or disease
development. Growing Prevalence Raises Concerns
Even though the risk
to humans is currently low, researchers say that the continued spread of CWD in
wildlife makes surveillance and disease control efforts more important.
"The more the disease spreads in animals, the more opportunities there are
for exposure," says Schaetzl.
"Risk is linked to prevalence."
Researchers at
UCalgary are also working on potential ways to reduce transmission among cervid
populations. Early vaccine studies using
mouse models that mimic infection in deer and elk have produced encouraging
results. Vaccinated animals shed fewer
infectious prions during both the early and later stages of disease and
survived longer following exposure.
"If we can
reduce shedding, we may be able to reduce transmission," says
Hannaoui. "That could have significant
effects on the population level of cervids." As chronic wasting disease
continues to expand, researchers say it remains essential to better understand
how prion diseases spread and evolve, including the possibility of silent or
unusual infections. That knowledge could
play an important role in protecting wildlife and supporting public health
efforts in the future.
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