From the field to the lab: The National Microbiology Laboratory tackles deadly mouse disease

July 28, 2023

Did you know that coming into contact with mouse droppings can be fatal?

At the Public Health Agency of Canada’s National Microbiology Laboratory (NML), protecting people in Canada from hantavirus means working on the problem from various angles. This involves multiple scientists, each with different specialities, who put in time not only in the lab, but also out in the field.

Several hantavirus cases occur in Canada each year and approximately one in three people who are infected die. The severity of the virus underscores the need for continued surveillance, testing and research, all of which are done at the NML.

What is hantavirus?

Hantavirus is a virus found in deer mice in Canada and is most commonly transmitted to people when they inhale virus particles from rodent urine, droppings or saliva that have been released into the air, or through contact with nests and dead mice.

Cases occur most frequently in the spring when people open up cottages and clean out outlying buildings such as sheds. These are places that can provide a refuge for rodents over the winter, and it is common to find mouse droppings or other evidence of their presence, which puts people at risk of hantavirus infection.

While infections are rare, hantavirus can cause severe respiratory distress syndrome which may require hospitalization and medical interventions to support breathing.

In the lab

The NML is Canada’s National Reference Laboratory, which means it tests all the hantavirus samples collected in Canada. While diagnostic testing can be safely done in the lower containment level laboratories, much of the research is done in the highest containment Level 4 labs, including research involving deer mice. Since hantavirus is an infectious pathogen that can pose a high risk of life-threatening disease, the Level 4 lab is used for biosafety and biosecurity reasons.

Dr. David Safronetz, Chief of Special Pathogens at the NML, and his team are attempting to better understand what drives hantavirus transmission from rodents to humans.

They are looking into methods to try to slow or prevent transmission of the virus, through the development of human and animal vaccines. They are also working on developing treatments to reduce the severity of disease and increase survival rates.

“Rodent-borne diseases such as hantavirus have the potential to see an increase because of climate change. Our ability to do research in advance can hopefully prevent future outbreaks and help us to protect the health of people in Canada,” says Dr. Safronetz.

Looking to the future and how climate change is affecting the spread of diseases, this research helps scientists to be one step ahead.Looking to the future and how climate change is affecting the spread of diseases, this research helps scientists to be one step ahead.

In the field

The NML’s hantavirus work is not limited to the lab. The Field Studies section within the lab does animal surveillance for hantaviruses on behalf of provinces and territories, municipalities and independent organizations, as requested. NML scientists go out into the field to collect samples for laboratory testing.

“As hantavirus infections are quite rare, surveillance work can give us information about where the sources of the virus may be and how common it is in certain areas,” says Dr. Heather Coatsworth, Chief of Field Studies at the NML. “This information is used to increase educational and awareness materials in select areas as preventative tools.”

When an outbreak occurs, a team from the NML’s Field Studies section goes to the area and completes on-site testing of animals to determine the severity of risk and potential of spread. They work with the Special Pathogens team in the lab to complete diagnostics. This allows them to quickly respond to outbreaks and prevent further spread.

How to prevent infection

The scientists stress that prevention is the best way to stop hantavirus infections. When opening cabins or cleaning out older outbuildings, take these preventative measures to significantly reduce your exposure risk:

  • Create ventilation by opening windows and doors
  • Use personal protective equipment (masks and gloves)
  • Avoid creating aerosols – don’t sweep up or vacuum dry droppings in areas that have clear evidence of mouse infestation
  • Clean up by spraying a 10% bleach solution directly onto the droppings, nest, or dead mice, allow for a 5-minute contact time, and pick up items and deposit them into a sealed plastic bag
  • Dispose of the sealed bag and personal protective equipment used in the cleaning process
  • Take steps to prevent rodents from getting into buildings by blocking small openings