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July 15, 2020

Researchers focus on COVID-19 virus in animals

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Veterinary researchers continue to investigate the COVID-19 virus in animals and how the virus interacts between humans and animals.

The study “Susceptibility of ferrets, cats, dogs, and other domesticated animals to SARS–coronavirus 2” was conducted by researchers at the Chinese Academy of Agricultural Sciences Harbin Veterinary Institute.

The findings, which were published May 29 in the journal Science, showed that SARS-CoV-2 infects the upper respiratory tract of ferrets but is poorly transmissible between individuals. In cats, the virus replicated in the nose and throat and caused inflammatory changes deeper in the respiratory tract. In addition, airborne transmission occurred between pairs of cats under the experimental conditions. Dogs appeared not to support viral replication well and had low susceptibility to the virus, and pigs, chickens, and ducks were not susceptible to SARS-CoV-2.

Also, in May, scientists in the U.S. and Japan reported that cats in a laboratory setting can readily become infected with SARS-CoV-2 and may be able to pass the virus to other cats.

Dr. Yoshihiro Kawaoka, professor of pathobiological sciences at the University of Wisconsin-Madison School of Veterinary Medicine, led the study, published May 13 as a letter to the editor in the New England Journal of Medicine.

Researchers obtained a SARS-CoV-2 isolate from a human patient and used it to generate a high dose of purified virus, which they then directly inoculated in the nasal cavity, trachea, and eyes of each of three cats. The following day, the researchers swabbed the nasal passages of the cats and were able to detect the virus in two of the animals. Within three days, the researchers detected the virus in all of the cats.

The day after the researchers administered the virus, they placed another cat that hadn’t been administered SARS-CoV-2 virus in each of the first three cats’ cages.

Each day, the researchers collected nasal and rectal swab samples from all six cats to assess them for the presence of the virus. Within six days, all of the cats were shedding virus. However, none of the rectal swab samples contained virus.

Each cat shed SARS-CoV-2 from its nasal passages for up to six days. None of the cats showed signs of illness, and all of the cats ultimately cleared the virus.

“That was a major finding for us—the cats did not have symptoms,” said Dr. Kawaoka. He is also helping lead an effort to create a human COVID-19 vaccine.

In another investigation, pet owners who bring their animals to the Cummings School of Veterinary Medicine at Tufts University can choose to participate in the Coronavirus Epidemiological Research and Surveillance study.

Pets of consenting owners will have nasal and oral swab samples collected and tested for SARS-CoV-2. The study is also seeking area pet owners to test their animals at home. Volunteers receive a kit and are asked to collect swab samples over a two-week period and return them to the university.

A very small number of animals have tested positive for the virus, so even one presumptive-positive result would provide invaluable information, according to Kaitlin Sawatzki, PhD, animal surveillance coordinator for the study.

“The more we know what a virus looks like that can hop species, the better the chances of preventing it,” said Dr. Sawatzki, a postdoctoral scholar in the laboratory of Dr. Jonathan A. Runstadler at the Department of Infectious Disease and Global Health at Cummings.