Animals Can Form Viral Reservoirs Where Covid Variants Breed

GENEVA, Switzerland, March 7, 2022 (ENS) – SARS-CoV-2, the virus that causes COVID-19, is still spreading among people globally as we enter the third year of the coronavirus pandemic. The risk of future variants is high and could be multiplied by the spread of SARS-CoV-2 to wildlife, resulting in the formation of animal reservoirs.

Current knowledge indicates that wildlife does not play a significant role in the spread of SARS-CoV-2 in humans, but spread in animal populations can affect the health of these populations and may drive the emergence of new virus variants, three of the world’s most important animal and human health organizations are warning today.

The World Health Organization, WHO, in Geneva; the World Organization for Animal Health, OIE, in Paris; and the Food and Agriculture Organization, FAO, in Rome, issued a joint alert this morning calling on all countries to take steps to reduce the risk of SARS-CoV-2 transmission between humans and wildlife with two goals – reducing the risk of variant emergence and protecting both humans and wildlife.

In addition to domestic animals like dogs and cats, free-ranging, captive or farmed wild animals such as minks and ferrets, North American white-tailed deer and large cats, gorillas, hyenas and otters in zoos, sanctuaries, and aquariums have been infected with SARS-CoV-2.

Farmed mink and pet hamsters have been shown to be capable of infecting humans with the SARS-CoV-2 virus and a potential case of transmission between white-tailed deer and a human is currently under review.

Studies have shown that at least one-third of wild white-tailed deer in the United States have been infected with SARS-CoV-2, initially through several human-to-deer transmission events.

The SARS-CoV-2 lineages detected in white-tailed deer have also been circulating in close-by human populations. White-tailed deer have been shown to shed virus and transmit it between each other, but their ability to transmit the virus to humans is still being studied.

A large Canadian study published on February 22 found “the first evidence … deer-to-human transmission,” the authors state in a preprint of their study on BioRxiv (say Bioactive) website.

Scientists with universities and government agencies in Ontario, Quebec and Manitoba discovered “a new and highly divergent lineage of SARS-CoV-2.”

“This lineage has 76 consensus mutations, including 37 previously associated with non-human animal hosts, 23 of which were not previously reported in deer,” the authors state. “Together, our findings represent the first evidence of a highly divergent lineage of SARS-CoV-2 in white-tailed deer and of deer-to-human transmission.”

Farther south, at Texas A&M University, researchers have been investigating how animals are involved in the transmission of SARS-CoV-2 since the summer of 2020, particularly in “captive cervid” facilities where deer are bred. There are more than 10,000 captive cervid facilities throughout the United States, according to The Wildlife Society, and more than 500 of these facilities are in Texas.

“Captive cervid facilities are part of an industry that involves raising deer to be used as breeding stock or for hunting,” said John Tomecek, Texas A&M AgriLife Extension Service wildlife specialist in the College of Agriculture and Life Sciences.

“Disease transmission is a concern anywhere animals are kept close together, and research has shown there is a correlation between their population density and the rate of transmission,” Tomecek said. “There have not only been instances of captive animal-to-animal disease transmission, but also transmission between captive animals and wild populations. SARS-CoV-2 has had an impact on other wildlife, including some endangered species.”

Tigers are endangered, and we know they can be infected with the virus. In June 2021, two lions at India’s Vandalur Zoo reportedly died after being infected with covid. In January, two white tiger cubs died of it in a zoo in Lahore, Pakistan. And big cats around the United States have been sickened.

The first instance of a tiger being infected with COVID-19 was found at the Bronx Zoo in New York City in March 2020. Samples from this tiger were taken and tested after several lions and tigers at the zoo showed symptoms of respiratory illness. Public health officials believe these large cats became sick after being exposed to a zoo employee who was actively shedding virus.

The big cats at the Bronx Zoo with symptoms did not infect people and all the infected animals recovered, according to the Wildlife Conservation Society, which manages all New York’s zoos.

But in September 2021, the Delta variant nearly killed a lion during the Smithsonian National Zoo’s covid outbreak when a contagious strain of the virus, likely from human source, infected nine lions and tigers.

Now, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service is engaging volunteer zoos, aquariums, and wildlife facilities to participate in a SARS-CoV-2 Serology Study to identify animal species that may be at risk of SARS-CoV-2 and determine which species to prioritize for vaccination.

“We will also assess the effectiveness of current biosecurity practices in mitigating SARS-CoV-2 spread and examine the role peridomestic wildlife may play,” APHIS said.

WHO, OIE and FAO are urging authorities in all countries to adopt relevant regulations and disseminate previously released recommendations to people working in close contact with or handling wildlife, including hunters and butchers; and the general public.

Personnel working closely with wildlife should be trained to implement measures that reduce the risk of transmission between people and between people and animals, using WHO advice on how to protect oneself and prevent the spread of COVID-19, and OIE and FAO guidelines on the use of personal protective equipment and good hygiene practices around animals, including good hygiene practices for hunters and butchers.

“Current evidence suggests that humans are not infected with the SARS-CoV-2 virus by eating meat. However, hunters should not track animals that appear sick or harvest those that are found dead. Appropriate butchering and food preparing techniques, including proper hygiene practices, can limit transmission of coronaviruses, including SARS-CoV-2, and other zoonotic pathogens,” the three health organizations explained.

FAO, OIE and WHO stress that the public should be educated about contact with wildlife. “Some wild animals may come close to human settlements and residential areas. As a general precaution, people should not approach or feed wild animals or touch or eat those that are orphaned, sick or found dead (including road kills). Instead, they should contact local wildlife authorities or a wildlife health professional,” they said.

“It is also crucial to safely dispose of uneaten food, masks, tissues, and any other human waste to avoid attracting wildlife, especially to urban areas and, if possible, keep domestic animals away from wildlife and their droppings,” they warned.

The three agencies encourage countries’ national animal and human health services to adopt these measures:

  • Encourage collaboration between national veterinary services and national wildlife authorities, a partnership key to promoting animal health and safeguarding human and environmental health.
  • Promote monitoring of wildlife and encourage sampling of wild animals known to be potentially susceptible to SARS-CoV-2.
  • Share all genetic sequence data from animal surveillance studies through publicly available databases.
  • Report confirmed animal cases of SARS-CoV-2 to the OIE through the World Animal Health Information System.
  • Craft messages about SARS-CoV-2 in animals with care so that inaccurate public perceptions do not negatively impact conservation efforts. No animal found to be infected with SARS-CoV-2 should be abandoned, rejected, or killed without providing justification from a country- or event-specific risk assessment.
  • Suspend the sale of captured live wild mammals in food markets as an emergency measure.

“Our organizations emphasize the importance of monitoring mammalian wildlife populations for SARS-CoV-2 infection, reporting results to National Veterinary Services, who report these findings to the OIE, and sharing genomic sequencing data on publicly available databases,” they said.

“Countries should also adopt precautions to reduce the risk of establishment of animal reservoirs and potential acceleration of virus evolution in novel hosts, which could lead to the emergence of new SARS-CoV-2 variants,” the three agencies said. “Such measures will preserve the health of precious wildlife as well as humans.”

Featured image: A herd of white-tailed deer feed in a New York field near the Pennsylvania border. Some of the white-tailed deer in New York, Illinois, Michigan, and Pennsylvania have tested positive for SARS-CoV-2, the virus that causes COVID-19. September 18, 2020 (Photo by Paul Cooper)

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