Cat and dog owners suffering from Covid-19 can pass their illness onto their feline and canine companions, according to a small study released Friday.

The new coronavirus is a "zoonotic" infection -- meaning it has jumped into humans from animals -- and while there is little sign that pets play a major role in spreading the virus, there is growing evidence that cats, dogs and even tigers may catch it.

In the latest preliminary research, which has not been peer reviewed, veterinary science experts in Canada tested the pets of a group of people with a confirmed Covid-19 diagnosis.

In a first group, they took swabs from 17 cats, 18 dogs and one ferret whose owners had a diagnosis within two weeks. These were all negative for a current illness, except one unclear result.

Then they gave blood antibody tests to eight cats and 10 dogs, whose owners were outside the two-week window, comparing these to control samples taken from the same animals before the pandemic.

Among the cats the results indicated presence of IgG or IgM antibodies in four (50 percent) and three (38 percent) respectively, while two dogs also tested positive (20 percent).

All cats and one of the dogs with antibodies were reported to have shown signs of respiratory or other illness at the same time as their owners.

"While eligible participant number was limited by relatively low human transmission rates in the study area, these preliminary results suggest that a substantial proportion of pets in households of persons with COVID-19 end up developing antibodies," said study co-author Dorothee Bienzle, Professor of Veterinary Pathology at the University of Guelph in Ontario.

Independent experts commenting on the research, which will be presented at the European Society of Clinical Microbiology and Infectious Diseases Conference on Coronavirus Disease later this month, said the sample size was too small to draw broad conclusions and that pet owners should not be alarmed.

Sally Cutler, Professor of Medical Microbiology, University of East London said there was not enough evidence to warrant people attempting to isolate from their animals.

"Pets can be a source of comfort for humans especially when unwell," she said, adding that it had not yet been demonstrated whether pets could be a source of human infection.

Domestic cats and dogs from Europe to the US have tested positive for the virus during the pandemic, while in April New York's Bronx Zoo said a tiger had caught the virus, probably from an asymptomatic caretaker.

The World Health Organization has said it was unclear whether infected animals pose a risk to humans.

Outbreaks in farms of ferret-like mink, however, have raised concerns of transmission to humans.

At least two farm workers in the Netherlands were found to be infected with Covid-19 in May, most likely by the mink, with the WHO saying they could be the "first known cases of animal-to-human transmission".