Farmers and the public in general should be aware of the differences between possible contamination of animals by Covid-19, and actual infection in animals, for which no evidence has been seen yet.

A member of the Veterinary Council of Ireland has said that: “To date, there has been absolutely no evidence that [Covid-19] has infected any animal other then humans”.

Vet Bill Cashman told AgriLand that there has been confusion over this point, as traces of the virus have been found in some animals. However, this constitutes contamination, rather than infection, Cashman explained.

There has been confusion, because there was some virus isolated from dogs, cats, and tigers, but there was no evidence that it actually infected them and was able to replicate inside them, or that they multiplied the virus and then spread it back.

“It’s almost the same as if they were contaminated, like a door handle or another surface. In other words, it got onto their fur, got into their nose, or they swallowed it and it was found in the feces,” the vet said.

Cashman explained: “These were very sensitive tests and those animal went negative [for Covid-19] very quickly.”

The virus does seem to have a – very negligible – physiological effect on cats, according to some tests, but this still occurs without infection taking place.

A couple of cats did develop antibodies. That means the virus got past the lining of the gut and the lining of the respiratory system, and the immune system made antibodies in response, but they still got no illness and they got no sickness from it.

As for cattle, sheep and pigs, there is no evidence that Covid-19 even has this type of mild effect. Experiments in China, which saw chickens, ducks, pigs, dogs and cats given “massive doses” of the virus found no uptake of infection, and only a mild reaction in the cats.

“You should treat animals like they could be contaminated like a surface, but not as if they are multiplying the infection and spreading it back out like you and I would do if we became infected,” Cashman explained.

The vet said that the concern, where animal contamination is concerned, would be people working in close proximity to contaminated animals picking up the virus, such as farmers.

However, Cashman said that the chances of this happening are “very, very low, hardly worth measuring, but a scientist would have to measure it because it could possibly happen”.

He also noted that there has been “no pattern” of the virus being detected in domestic animals in households where an infected human was living.

To be on the safe side, Cashman encouraged farmers, pet owners and anyone in close proximity to animals to continue to observe proper hand hygiene and general hygiene.

How viruses work

To explain why different animals (including humans) are infected by different viruses in different ways, Cashman used the example of foot-and-mouth disease.

“Foot-and-mouth infected cloven-hoofed animals, such as cattle, sheep and pigs. The foot-and-mouth virus can actually get into a horse and cause an antibody reaction, but the horse never gets sick.

“The reason for that is that a horse’s cell doesn’t have the weak spot that the foot-and-mouth virus can exploit. With cloven-hoofed animals, the virus has evolved to get into those animals’ cells,” he outlined.

‘Lock and Key’

“Think of it like a lock and a key. The virus has a key and is hunting for a lock that it can open and get into a cell,” the vet explained.

“Once it gets into the cell, it takes over all of that cell’s functions to make more virus. The cell, instead of doing what it should be doing, is producing more viruses until it swells up, ruptures, and those viruses infect the next cell, and so on.

Cashman concluded his explanation by saying: “Finally, there’s enough damage done to raise your temperature, and that’s when you start getting sick.”