COVID-19 in mink farm reveals early lung damage

Researchers and veterinary pathologists from Wageningen Bioveterinary Research (WBVR, part of Wageningen University & Research), together with Royal GD and Utrecht University, followed the course of SARS-CoV-2 infection in mink. Their findings show how the disease develops, spreads and interacts throughout the whole body often before it becomes clinically visible. “Deep inside the lungs, damage is already unfolding before the first signs of illness appear,” says WBVR-researcher and veterinary pathologist Sandra Vreman.

On a mink farm in the Netherlands, animals were studied at different stages of clinical disease: apparently healthy, visibly ill, and deceased. What looked like healthy animals often told a different story under the microscope. Even without clinical signs, mink showed clear and sometimes severe lung damage. Their lungs revealed diffuse alveolar damage, a sign connected to severe COVID-19 in humans. Alveoli are filled with fluid, lung-lining cells broke down, and hyaline membranes formed, signalling acute injury. The disease begins quietly, progressing beneath the surface before it can be seen.

The findings were recently published in Frontiers of Veterinary Science.

Mink mirror key aspects of SARS-CoV-2 infection in humans. In both species, the virus targets the respiratory tract, triggering similar patterns of lung injury and immune response. The early stages closely resemble those seen in hospitalised COVID-19 patients.

At the same time, important differences emerge. Unlike in humans, pathologists did not observe widespread thrombosis and fibrotic lung damage in mink. “These contrasts are just as valuable,” according to Vreman. “They help us understand differences in duration and treatment of disease and which disease processes are universal and which are shaped by species-specific biology.”

The study also revealed an additional layer of complexity. Many mink were infected with Aleutian disease virus (ADV), a chronic infection that affects the immune system. Animals with higher levels of ADV showed more severe lung damage. “This reflects what we also see in humans: when the immune system is already under pressure, COVID-19 can take a more severe course.”

This research shows how infections such as SARS-CoV-2 can spread and progress even when no clinical signs are visible. It underlines the importance of early detection, surveillance, pathology and understanding transmission dynamics across species. By studying naturally infected mink, researchers gained insights that go beyond a single species.

Understanding disease in animals is not separate from protecting human health, it is part of the same system. This is the essence of the One Health approach: connecting animal and human health to better prepare for future outbreaks.