Infection of Dogs with SARS-CoV-2

With the emergence of the coronavirus pandemic (also called SARS-Cov-2) in December 2019 in Wuhan came a flood of questions about treatment, symptoms, susceptibility, and more. Naturally, the questions that surrounded—and continue to surround—SARS-CoV-2 are logical, basic questions that need to be answered—one of those questions, however, wasn’t as run of the mill.

How exactly, one study asks, does SARS-CoV-2 affect domestic dogs and cats?

That question doesn’t just derive from genuine, human curiosity, but rather, from past experience and precedent. In 2003, the closely related SARS-CoV had been detected in domestic cats and dogs. That being said, little is known about the susceptibility of domestic pet mammals to SARS-CoV-2. That question, however, has been attempted to be answered.

In a study published on PubMed.gov on May 14, 2020, a team of doctors, researchers, and medical professionals set out to see if domestic dogs and cats are susceptible to the SARS-Cov-2 virus.

It’s reported that two out of fifteen dogs from households with confirmed cases of COVID-19 in Hong Kong SAR were found to be infected using quantitative RT-PCR, Serology, sequencing the viral genome, and in one dog, virus isolation.

Understanding the Cases

The first case was a 17-year-old neutered male Pomeranian. This dog has a large number of preexisting disease, including but not limited to, a Grade II heart murmur, systemic and pulmonary hypertension, chronic renal disease, hypothyroidism, and hyperadrenocorticism. His owner was a 60-year-old woman who developed COVID-19 symptoms in early February 2020. The dog was transferred to a holding facility and had oral, nasal, and rectal swabs collected as well as fecal samples. The nasal swab was what detected the SARS-CoV-2-RNA, but given the low viral load, it was deemed unlikely that the virus culture would be successful in human patients with COVID-19.

The second case was a 2.5-year-old German Shepherd that was in good health and was taken from a household where the owner developed symptoms in early March. Oral and nasal swabs were collected, and both tested positive. Then rectal swabs were collected and tested positive, all with higher Ct values (a lower viral load) than those obtained through the oral and nasal swabs. A second dog from the same household was tested and was negative.

Both dogs in each case had antibody responses detected through the use of plaque reduction neutralization assays.

The Results of the Study: What Happened

What these two cases in Hong Kon demonstrate is that dogs can acquire infections in households with SARS-CoV-2 infected humans. In the dogs’ viral genetic sequences of the virus, both were identical to the virus detected in human cases—that being said, these animals remained asymptomatic during quarantine.

This suggests that there can be instances of human-to-animal transmission of SARS-CoV-2 but there is not enough evidence to suggest that infected dogs can transmit the virus to other animals or back to humans.