- A small study that repeatedly tested the pets of people with COVID-19 suggests that 31% of dogs and 40% of cats acquired a SARS-CoV-2 infection.
- Neutered pets or those that shared a bed with a human with the infection were more likely to contract the infection.
- The study reinforces the message that people with COVID-19 should avoid close contact with their pets if possible.
- There remains no evidence that pets with the infection can pass it on to people or other animals.
Researchers in Brazil have discovered a higher than expected incidence of SARS-CoV-2 infection among the cats and dogs of people with COVID-19.
However, there remains no evidence that SARS-CoV-2, the virus that causes COVID-19, can transmit from pets to people.
Between May and October 2020, scientists at the Evandro Chagas National Institute of Infectious Diseases, Oswaldo Cruz Foundation, in Rio de Janeiro, recruited 21 patients with confirmed COVID-19 who shared their household with a pet cat or dog.
These patients were male or female aged 18 years and older, with COVID-19.
There were 29 dogs and 10 cats in total. The scientists took nasal, throat, and rectal swabs from the animals during an initial home visit and two further visits around 15 and 30 days later.
They also collected blood samples to test for the presence of antibodies capable of neutralizing the virus.
Pets in 10 of the households (around 50%) tested positive for the virus. In total, there were nine dogs (31% of all the dogs) and four cats (40% of all the cats) that contracted the infection.
The animals tested positive between 11 and 51 days after the onset of symptoms in their respective human owner or carer.
The researchers detected neutralizing antibodies in the blood of one dog and two cats.
Out of the 13 animals that tested positive, six showed mild, temporary symptoms, while the remainder showed no symptoms.
The study results appear in the journal PLOS ONE.
“There is now an increasing number of studies of pets around the world being published that suggest that asymptomatic infection of pets, some rather larger than this small case series, is quite common,” said Professor James Wood, Ph.D., B.Vet.Med, head of the Department of Veterinary Medicine at the University of Cambridge in the United Kingdom, who was not involved in the current study.
“None have provided any suggestion of onward transmission to other pets or humans, however,” he told Medical News Today.
According to the authors, the proportion of pets that tested positive in this study was higher than in similar studies in other countries worldwide.
They attribute this to their repeated sampling over a period of around a month, as opposed to a single sample collection in the other studies.
Their analysis suggests that neutered pets, and pets that shared a bed with the person with the infection, were more likely to acquire the virus.
They write that neutered cats and dogs are likely to spend more time within the confines of the home, which may make them more vulnerable to infection.
“People with COVID-19 should avoid close contact with their pets during the time of their illness,” they conclude.
The Centers for Disease Control and Prevention (CDC) emphasize that the latest research suggests the risk of pets spreading COVID-19 to people is low.
It says there is no evidence that the virus can spread to people from the skin or hair of pets.
However, the CDC advises owners not to let their pets interact with individuals outside their households during the pandemic.
“If a person inside the household becomes sick, isolate that person from everyone else, including pets,” it adds.
People who have COVID-19 and need to care for their pet or be around animals should wear a mask and wash their hands before and after interacting with them, it advises.
Highly sensitive tests
The authors of the study in Brazil caution that their results do not prove the presence of infectious virus in the samples.
They used highly sensitive polymerase chain reaction tests to amplify viral RNA. This means that positive samples may have contained only residual fragments of SARS-CoV-2 and not the infectious virus.
Researchers need more extensive cell culture testing to confirm if any viral particles in the samples can cause an infection and replicate inside cells.
The researchers conclude:
“More longitudinal and experimental studies, including virus isolation in cell cultures, are necessary for a better understanding of the role of cats and dogs in SARS-CoV-2 spreading.”