Twenty-one years ago, one week after terrorists hijacked four commercial jets in the September 11 attacks on America, federal officials also responded to the worst bioterrorism attack on American soil.
Anthrax-laced anonymous letters had been mailed to members of the media and Congress, and contamination from those letters led to the deaths of five Americans as well as illness in 17 others. When federal officials closed the books on the “Amerithrax” investigation nine years later, it was two years after the primary suspect in the attack had committed suicide.
Anthrax had been used as a bioweapon, and that attack led Congress to strengthen safeguards for biological select agents and toxins, including anthrax and brucellosis – diseases most commonly associated with animals. Anthrax and brucellosis are also classified as zoonotics, meaning diseases that can spread between animals and people. Six out of every 10 infectious diseases in people are zoonotic.
A few years after the anthrax attack, public health and veterinary officials gathered to discuss the connections between animal health, human health, and environmental health, and advocated for a collaborative approach to address these health threats, incorporating all three sectors into a “One Health” perspective, and working on a varied scale, from local to global.
Fast-forward to 2017, when a group of scientists with the U.S. Centers of Disease Control and Prevention, U.S. Department of Agriculture, and the U.S. Department of Interior convened a meeting in Washington, D.C. to identify zoonotic diseases of greatest national concern as agreed upon by human, animal, and environmental health experts under the One Health approach.
Development of the priority zoonotic list considered these primary factors: pandemic/epidemic potential, severity of disease, economic impact to the United States, potential for introduction or increased transmission, and national security (the potential of the disease to be used for bioterrorism).
That meeting led to creation of a ranked national priority list of zoonotics, as follows:
1. Zoonotic influenza (influenza A viruses are found in many species, from birds to whales)
2. Salmonellosis (a bacterial-caused foodborne disease that affects wildlife and domestic livestock as well as humans)
3. West Nile virus (the leading cause of mosquito-borne disease in the US)
4. Plague (resulting from the bacteria Yersinia pestis, often found in wild rodents, with transmission to humans often caused by domestic cats, which are very susceptible to infection)
5. Emerging coronaviruses (including severe acute respiratory syndromes such as SARS and MERS)
6. Rabies (a nearly universally fatal disease)
7. Brucellosis (found in bison and elk in this region, occasionally causing outbreaks in cattle, and is responsible for about 100 human cases per year in the US)
8. Lyme disease (the most common vector-borne pathogen in US, caused by ticks)
The priority list was developed in 2017 – several years before the coronavirus pandemic began, but the 2017 list and the One Health approach has remained a cornerstone of infectious disease monitoring since the pandemic began. While much attention has focused on the availability of coronavirus tests and vaccine for the human population, other crucial work was taking place in the animal health and environmental health sectors.
Environmental health officials began a program to monitor wastewater systems to detect coronavirus. One of the complicating factors with this coronavirus is that a person could remain without symptoms while actively shedding the virus and infecting others, so wastewater-based epidemiology became a method to predict case levels and hospitalizations, and captured data from seasons and waves of cases as the pandemic proceeded.
At the same time, experimental coronavirus vaccines were developed for a variety of wild animal species, with particular attention focused on wild feline species which seem highly susceptible to the virus. Vaccinating wild animals could not only improve outcomes for rare species but could lessen the chance of further virus mutations that could spread back to humans. Multi-species experimental vaccines are undergoing testing in zoos and animal sanctuaries throughout the world.
When mink farms began experiencing a SARS-CoV-2 outbreak (the official name of the new coronavirus), officials with the USDA Animal and Plant Health Inspection Service (APHIS) began testing wild and domestic animals on and near mink farms in Utah. Their effort found that 72% of the animals sampled harbored at least one coronavirus, including wild mink near the farms, as well as domestic cats, mice, raccoons, and striped skunks. The unexpectedly high seroprevalence rate in these locations indicate they “could be potential hot spots for future trans-species viral spillover and the emergence of new pandemic coronavirus.”
It’s routine for wildlife and veterinary officials to collect nasal swabs and/or blood samples to test animals for antibodies against a variety of viruses, collecting samples from hunter-killed big game animals, animals dead from vehicle strikes, both wild and domestic animals near zoos, and from other wildlife facilities. Those routine disease surveillance efforts added to further documentation of coronavirus in animal populations, putting health officials on notice that with the virus circulating among wild animal populations, and in the environment, eradication efforts would be unlikely to succeed.
As the coronavirus outbreak spread, researchers around the world began testing captive animals to learn which species may be susceptible to the disease. When an APHIS research project found that white-tailed deer were able to shed the virus in captivity, sampling efforts in wild deer were initiated in four midwestern states, revealing that about 40% of the animals sampled tested positive for the virus. Testing spread to deer populations in other states, with reports of 30-40% positivity, and coinciding with peaks in human infections. While it appeared the virus spilled over from humans to white-tailed deer on at least six separate occasions, the deer were also spreading the infection among themselves. Of the 30 states that have been sampling their deer populations, 24 have found positive cases. Earlier this year, a mule deer in Utah tested positive for the virus.
Routine samples taken by veterinarians on domestic animals provided further insights. German researchers used excess lab submission materials drawn by veterinarians during routine diagnostic sampling on cattle to detect coronavirus, suggesting that cattle became infected after contact with infected humans during the peak of the pandemic. SARS-CoV-2 detections in the United States now include a wide variety of wildlife species, from otters and manatees, to beaver and lynx.
This coronavirus pandemic has resulted in a real test of the usefulness of a One Health strategy in addressing a zoonotic disease. While most of the individual pieces to this puzzle have gone under the public’s radar, in my view, the One Health response to a zoonotic-caused global pandemic has confirmed the wisdom of uniting human, animal, and environmental health response.
Cat Urbigkit is an author and rancher who lives on the range in Sublette County, Wyoming. Her column, Range Writing, appears weekly in Cowboy State Daily.
