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November 01, 2021

Studies ongoing into effects of SARS-CoV-2 variants on animals

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The SARS-CoV-2 delta variant is more contagious among humans, and some data suggest it may cause more severe illness than previous variants in unvaccinated people.

As that variant spread through the U.S., researchers continued work to understand the effects of SARS-CoV-2 and its variants on animals.

Dr. Casey Barton Behravesh, director of the Centers for Disease Control and Prevention’s One Health Office in the National Center for Emerging and Zoonotic Infectious Diseases, said that many of the SARS-CoV-2 infections reported in dogs, cats, and captive animals in zoos and aquaria since July 2021 had been caused by the delta variant. CDC officials are among the federal authorities collaborating to understand the risk presented by the variant, she said.

The federal SARS-CoV-2 Interagency Group’s work includes efforts to understand how SARS-CoV-2 and its variants spread between animals and between people and animals, and they are working to learn more about the effects of variants on animals, Dr. Barton Behravesh said. So far, most nonhuman animals with SARS-CoV-2 infections—regardless which variants are involved—had been exposed to infected people, she said.

Tabby cat looking at the camera

As of Aug. 17, the U.S. Department of Agriculture Animal and Plant Health Inspection Service reported 221 nonfarm animals had confirmed infections with SARS-CoV-2, and those figures do not distinguish among variants of the virus. These animals were 97 cats, 86 dogs, 18 tigers, six lions, five snow leopards, five otters, three gorillas, and a cougar.

SARS-CoV-2 outbreaks on U.S. mink farms also have killed thousands of the animals since August 2020.

University-based researchers also are trying to understand which animals are susceptible to SARS-CoV-2 and its variants.

Dr. Sarah Hamer, a veterinarian and epidemiologist at the Texas A&M University College of Veterinary Medicine & Biomedical Sciences, has led research on SARS-CoV-2 in pets, and her team in March discovered a dog and a cat infected with what is now known as the alpha variant of the SARS-CoV-2 virus. Her team was the first to announce the discovery of confirmed infections with the variant in both species.

The animals had developed sneezing prior to testing and appeared to recover to full health.

Dr. Hamer said in early September she expects the SARS-CoV-2 strains that infect humans will continue to spill over into animals.

Her team recently had been collecting samples for other projects, including research that could indicate whether feral cats spread SARS-CoV-2 among wild or feral animal populations. Because that study overlaps with the surge in the delta variant in humans, she said the study also may help address questions about the effects of that variant.

Dr. Hamer’s team also recently began collecting blood and swabs from deer in Texas to determine whether they have become exposed to the SARS-CoV-2 virus, and she hopes to have a mix of samples from wild and captive deer. She noted two prior studies in the U.S. in which researchers reported finding antibodies and viral RNA that suggest deer had been infected.

Dr. Sonia M. Hernandez, a professor of wildlife and wildlife diseases at the University of Georgia School of Forestry and Natural Resources, said during an Aug. 4 presentation for a CDC Zoonoses & One Health Updates conference call that results of a study she and colleagues conducted suggest skunks and raccoons were unlikely to be competent hosts for SARS-CoV-2. But she also noted in that call the study was conducted near the beginning of the pandemic, and she said more research was needed to understand how different SARS-CoV-2 strains may change the findings.

Dr. Barton Behravesh recommended that veterinarians monitor SARS-CoV-2 prevalence in their communities, keep up to date on information from the CDC, and ensure they and their staff are vaccinated. CDC officials also have previously recommended that people worried their pets could be infected with SARS-CoV-2 call ahead to their clinics to make appointments rather than arrive unannounced.

The AVMA has updated information about the SARS-CoV-2 virus and resources for veterinary professionals.