Ireland’s largest animal welfare organisation is preparing for what it says would be the first case of a prosecution of a pet-owner for allegedly abandoning guinea pigs and a goldfish.

The Irish Society for the Prevention of Cruelty to Animals (ISPCA) was called to a rented apartment in central Cork last Thursday by the lettings agent after the discovery of the six pets which were on their own.

One guinea pig was found already dead in the flat, while four others appeared malnourished and “absolutely terrified”. And the goldfish was not initially visible in a bowl of half-evaporated “filthy, dirty” water, said ISPCA senior inspector Lisa O’Donovan.

One of the guinea pigs taken into the care of the ISPCA after being found in an apartment in Cork. Photograph: ISPCA

Under the Animal Health and Welfare Act, ISPCA inspectors were designated as “authorised officers” five years ago, and handed powers similar to the gardaí for investigating suspected animal cruelty.

This includes the power to interview suspects under caution and take prosecutions, which on conviction can carry a maximum fine of €250,000 or a prison sentence of up to five years.

Ms O’Donovan told The Irish Times she was preparing for a prosecution in the goldfish and guinea pigs case, which she believed could be the first if its kind in Ireland.

“It is predominantly cats, dogs and horses [for which prosecutions are taken],” she said.

“I have never known a case regarding other domestic animals and I don’t believe my colleagues have either.”

Ms O’Donovan said the four surviving guinea pigs — which have been renamed Tina, Shirley, Billy and Greg — are recovering with an experienced foster carer who will help them “get over their ordeal in their own time”.

“They were very nervous and when we offered them food they wolfed it down like it was going out of fashion, which is sad to see, because they were clearly starving,” she said.

“The goldfish is doing well; he is staying with me. It took him a day or two to settle down, but thankfully he survived the transition. It must have been a breath of fresh air for him to have clean accommodation and food,” said Ms O’Donovan.

She said a file was being prepared for the Department of Agriculture, including photographic evidence and veterinary reports while efforts were underway to track down the pet-owner to be interviewed under caution.

It is not known if they are on holiday or have temporarily or permanently left the apartment, she said, adding that the pets may have been on their own for a week or more.

Two of the guinea pigs taken into the care of the ISPCA after being found in an apartment in Cork. Photograph: ISPCA

Once the file is completed, the Department of Agriculture will decide if it is to be sent forward for prosecution.

“My attitude is that if we get the evidence together and we have a strong case; abandonment is abandonment,” said Ms O’Donovan.

“Obviously, I’d be foolish to think that any judge in the country would take an abandoned goldfish as serious as other animals — which I think is shame, because it is a living being, who also depends on us to look after it.

“But certainly, in the case of the guinea pigs, the onus is on us [to pursue it], and we shouldn’t turn a blind eye and ignore it, simply because it is not your normal species.

“It may well be that there are other issues going on with the owner of these animals, but that is not an excuse to disregard their welfare and to not look after them.”