Chapter 1: The Rising Threat of White-Tailed Deer

Since the onset of the COVID-19 pandemic, scientists have been wary of potential new animal reservoirs for the virus. While they initially focused on small mammals such as rodents and raccoon dogs, the real concern has emerged from an unexpected source: wild deer.

White-tailed deer (Odocoileus virginianus) stand as one of the most notable conservation successes of the last century. However, some may argue that their resurgence has led to overpopulation. Native to North America, these impressive creatures were nearly hunted to extinction by the early 20th century. As agriculture expanded, their habitats diminished, leading to a significant decline in their numbers.

To combat this, various North American states implemented hunting regulations, fearing that they would lose these game animals entirely. They also initiated habitat preservation and introduced new deer into depleted regions, allowing populations to rebound.

Unfortunately, their primary predators, such as wolves and mountain lions, did not receive the same attention, resulting in their decline. While smaller predators like bobcats and coyotes do hunt deer, they generally target younger or weaker individuals, leaving the adult population largely unchecked. With a decreasing interest in hunting, deer numbers have surged, particularly in areas like southern New York and northern Pennsylvania, where densities reach around 30 to 35 deer per square mile—threefold the pre-European settlement estimates of 10 to 15 deer per square mile.

The unchecked deer population poses significant risks to the natural environment. As voracious herbivores, deer consume a wide array of vegetation, from grass and seedlings to saplings, leading to a decline in biodiversity. This loss affects not only the flora but also the fauna, as species like songbirds lose nesting sites, and larger herbivores such as elk and moose are pushed into smaller habitats.

Moreover, deer present considerable public health risks, carrying diseases such as Lyme disease, bovine tuberculosis, and chronic wasting disease, akin to mad cow disease. Additionally, deer-related vehicle collisions add to the hazards they pose.

To monitor these risks, researchers have collaborated with hunters for years, conducting wildlife surveillance by examining deceased deer. They assess the animals' age through dental analysis, measure antler sizes, perform nasal swabs for viral RNA testing, and collect blood samples for antibody studies. Although these activities are standard practice, the findings can be startling.

On July 2021, scientists from the US Department of Agriculture in Fort Collins, Colorado, reported that 40% of serum samples from wild deer had antibodies against Sars-CoV-2, even though the deer exhibited no illness.

Sampling efforts intensified with the support of hunting organizations, leading to significant findings. In Ohio and Iowa, nasal swab tests indicated that approximately one-third of sampled deer were positive for Sars-CoV-2. By the following spring, the virus had been detected in deer across a majority of U.S. states and several Canadian provinces.

However, the situation escalated further. In March 2022, researchers in Ontario reported a probable case of deer-to-human transmission of Sars-CoV-2. The infected individual carried a viral lineage closely related to that found in deer. While definitive proof of transmission was lacking, the possibility was strong.

White-tailed deer now stand as the third species confirmed to transmit Sars-CoV-2 to humans, following mink and hamsters. This revelation heightens the public health risks posed by uncontrolled deer populations and highlights the critical role of international wildlife surveillance, especially the contribution of hunting communities.

As noted in a podcast episode from This Week in Virology, the potential for viral variants to cross borders between Canada and the United States underscores the urgency of monitoring these populations.

These discoveries also advocate for the conservation of large predators like wolves in Eastern North America. The reintroduction of wolves in Yellowstone National Park demonstrated how stabilizing elk populations can benefit the entire ecosystem, including grizzly bears and mountain lions.

To prevent the deer population crisis from worsening, international collaboration is essential, and traditional conservation strategies may hold the key.

In this video, scientists reveal alarming rates of COVID infections among white-tailed deer and discuss the implications for public health.

Chapter 2: The Implications of Relaxing Restrictions

As researchers continue to study the dynamics of COVID-19 transmission in wildlife, concerns about premature relaxation of restrictions grow. The interplay between human activities and wildlife health remains crucial, especially as deer populations flourish.

This video examines the potential risks of relaxing COVID-19 restrictions too soon, particularly concerning the spread of the virus among outdoor populations of white-tailed deer.

If you're interested in learning more about the transmission of Sars-CoV-2 from animals to humans, consider reading the article below...

How COVID-19 Affected the Fur Industry

When high fashion became a public health concern.