Syrian Hamsters Lend a Paw to COVID-19 Research

It was early spring 2020 and things were looking bleak. COVID-19 cases were skyrocketing worldwide. Dr. Kyle Rosenke, a staff researcher at the National Institutes of Health, was uncertain whether his team would find the appropriate small animal model for timely coronavirus research. However, when Dr. Rosenke entered a lab studying COVID-19 infected hamsters, what he saw that day gave him and his colleagues a glimpse of hope on the disease-infested horizon.

“The moment I saw the lesions on those hamsters’ lungs, I knew that we might have found a fellow patient of COVID-19.” Dr. Rosenke said. His speculation at this moment was justified. Their discovery of coronavirus symptoms in Syrian hamsters established the latter as an important animal model for future COVID-19 research.

Small animal models are typically used in labs to study infectious diseases and their potential treatments. In doing so, researchers gain insight into viruses and later utilize this knowledge to help human patients. Ever since the onset of the pandemic, researchers have been in dire need of a small animal model to study the impact of the virus on human bodies. However, this is no easy task because some animals have high susceptibility to the virus showing life-threatening symptoms, while others display little to no signs of infection.

In the case of COVID-19, the primary standard for a good model organism depends on the animal’s susceptibility to the virus. Imagine burglars breaking into your house. If they have a set of keys to open your front door, the entry becomes very easy. The infection cycle for SARS-CoV-2 (the virus that causes COVID-19) starts with the virus interacting with ACE-2 receptors on the host cell surface. For SARS-CoV-2 posing as a burglar, ACE-2 receptors work as the keys to gain entry to our bodies. Once inside, the virus quickly hijacks the immune system, replicates itself, and fully infects the host. But just as you need to have a unique key to open a door, SARS-CoV-2 needs specific ACE-2 receptors to enter our bodies.

Early in the pandemic, scientists tested the response of ACE-2 receptors in various animals. However, lab mice showed no symptoms of illness to the virus suggesting that their ACE-2 receptors were not the perfect “keys” for SARS-CoV-2 entry. The scientific community also tried to make various genetic changes in the lab mice that made them more sensitive to viral infection. Simultaneously, labs across the world were competing to find reliable animal models without any genetic modifications. That’s when Syrian hamsters entered the scene.

“I would say that the Syrian hamster has proven to be by far the most reliable small animal model out there [for COVID-19 research],” claimed Dr. Rosenke who belongs to one of the earliest lab groups to use the Syrian hamster model.

The Syrian hamster proved to be a valuable model in this case because the animals become infected consistently and show visible illness symptoms. In addition, Syrian hamsters have ACE-2 receptors similar to those found in humans. Once infected, most hamsters develop mild to moderate disease symptoms. In the case of a mild infection, about 30% of a hamster’s lung will have signs of pneumonia. Whereas in more severe cases, around 70% of the lung will show the disease.

Scientists have continued to gain crucial insights into SARS-CoV-2 through the Syrian hamster model. One example is our improved understanding of how the virus is transmitted. When SARS-CoV-2 first hit the world, people had little understanding of how it wreaks havoc on our cells. Judging from its rapid spread, many scientists assumed the virus could most likely transmit through the air. Initially, there was no scientific proof for this assumption, but by using the Syrian hamster model, Dr. Julia R. Port and her team at the National Institute of Allergy and Infectious Diseases’ Rocky Mountain Laboratories effectively proved the virus can spread as small droplets in the air.

Nearly two years later,Syrian hamsters continue to lend their paws to research on COVID-19 transmission and prevention. Meanwhile, Dr. Port insists, “the most important lesson we learn from the Syrian hamsters is to get vaccinated if possible, wear a mask indoors, and stay safe!”