The story was about 4-year-old Malay tiger Nadia, who contracted COVID early in the pandemic, along with six other tigers at the Bronx Zoo – likely after being cared for by an asymptomatic zoo worker.
This was the first of what would become a steady stream of stories about animals that, like most of us, have contracted COVID. Among the animals that have, according to the US Centers for Disease Control and Prevention:
- Pets such as cats, dogs, ferrets and hamsters.
- Zoo animals like lions, tigers, snow leopards, otters, hyenas, hippos and manatees.
- Mink that lives on farms.
- Wildlife, including dozens of white-tailed and mule deer, black-tailed monkey, and giant anteater.
It is well known that Covid disease is no exception to the “zoonoses” diseases transmitted by animals to humans, or vice versa. It is believed to have spread from bats, pangolins, or raccoon dogs to humans, possibly via a medium such as a pet (although the controversial “lab leak” hypothesis has not been fully debunked).
Similar to COVID, the 2009 H1N1 “swine flu” pandemic is believed to have resulted from the mixing of pigs in North America and Europe, mixing strains of influenza. West Nile virus, which originated in arthropods and is transmitted by mosquitoes, was discovered in New York City in 1999 and has since become endemic to the United States. In monkeys, although it is believed that it originated in rodents.
The animals likely launched the COVID-19 pandemic, because they had so many others – but their role in that didn’t go away after that. The pathogen is now circulating in both groups, crosses and spreads again, even if such occurrences are relatively rare. And like humans, animals continue to shape epidemics, as new variants and sub-variants evolve in hosts with skin, fur, and feathers before attempting to break into the wider community.
Scientists are watching the animal kingdom for signs of what’s to come next.
The host is the host
Scientists recently began tracking the spread of COVID in animals on publicly available data dashboards. One, launched late last month by the Wildlife Conservation Society and Australian researchers at the University of Veterinary Medicine in Vienna, has so far documented 704 diagnoses of COVID-19 in animals worldwide, in 39 countries and 27 species.
From the revelation:
- 117 cat infections and 110 dogs have been documented in the United States
- Minks are among the most common animals identified with COVID. In Greece alone, 159 species of American mink have been diagnosed, as well as approximately 150 in Spain and 250 in Lithuania.
- Most of the animals were asymptomatic or had respiratory symptoms. Minks are most likely to die.
- Omicron sub-variants are the most common subspecies identified in animals, although delta cases have also been documented.
Dr. Mary Montgomery, a clinical instructor in the division of infectious diseases at Brigham and Women’s Hospital, a Harvard-affiliated facility in Boston, says the risk of contracting COVID from animals is minimal.
But it is real. COVID entered humans from animals — possibly in many patients from multiple encounters with animals in late 2019, according to a recent study — and can re-enter animals through humans in a process scientists call “zoonotic transmission.”
Just as the coronavirus can mutate in humans, it can mutate in animals. Thus, an animal with COVID can spawn a new variant or variant and pass it on to humans.
In a worst-case scenario, this new variant would be more transmissible than the currently prevalent omicron BA.5 adjuvant variant and even more immune-evading—perhaps even able to outsmart antivirals such as Paxlovid and monoclonal antibody therapies offered in hospitals and outpatient settings.
The most likely culprit in such a scenario would be a bird, due to its migratory nature.
“Birds can migrate and spread new pathogens quickly,” Montgomery says. “And there are certainly many cases in the literature of other coronaviruses that infect birds.”
Among the researchers monitoring the bird population: Dr. Raj Rajnarayanan, Assistant Dean for Research and Associate Professor at the New York Institute of Technology on the campus of Jonesboro University, Ark. He has created and maintained a number of COVID-related dashboards, including one on COVID in animals, filled with data from GISAID, an international research organization that tracks changes in COVID and the influenza virus.
While the majority of animal cases identified globally have been in mink, deer and domestic animals such as cats and dogs, Rajnarayanan recently indicated that COVID has already crossed into the bird population. The first two recently reported cases were identified in pelicans in China.
Omicron appears to be more susceptible to infection in chicken and turkey than the delta variant, he says, adding that bird transmission could eventually have “significant effects” such as new mutations, widespread spread of the virus, and effects on the food supply.
“Everyone wants to focus on mammal species,” he says. “Now the birds enter the picture. We want to monitor this closely.”
Ragnarayanan would like to see the USDA facilitate more frequent testing of farm animals. He also believes that the agency should provide protective equipment to farmers to reduce the possibility of transmission from farmers to farm animals, and vice versa.
“We’re almost in our third year — we don’t want this thing to go on forever,” he says.
Medical and veterinary professionals must be involved
As climate change continues, and animals and humans are forced to come into contact more regularly, outbreaks and spreads – whether it’s the coronavirus, bird flu, or a pathogen that humans don’t yet know about – are bound to happen and may well be the next pandemic.
Montgomery advocates the concept of “One Health,” which asserts that the health of people, animals, plants, and their common environment are inexorably intertwined.
Vets and doctors used to train together before the advent of the car, which led to doctors moving to bigger cities as hospitals and vets moved to rural areas, where they needed to care for farm animals, she says. Harvard used to be home to a veterinary school, as well as its own medical school, training students together.
Such interdisciplinary collaboration is needed again if we are to finally advance in the face of this pandemic – and prevent the next.
“We have to have the resources to not only think about human health, but to make sure we think about animal health,” she says, adding that humans often fail to worry about diseases in animals — until they get into humans.
Sometimes we don’t think about prevention, early mitigation, or containment. We only react as soon as something enters humans. Awareness is key here.”