Three sick puppies who were dumped in a cardboard box by a layby may have been “victims of the cruel puppy trade,” animal welfare rescuers fear.

One of the spaniel puppies, aged around eight weeks old, had already died when they were found without food or water by a cyclist who had stopped for a rest on Shopland Road in Rochford, Essex, on Saturday.

The grim discovery was made at around 4pm when the cyclist saw that one of the puppies was dead while the others were very skinny, according to the Royal Society for the Prevention of Cruelty to Animals (RSPCA) who are investing how they became abandoned.

Tests that were soon carried out by vets near Southend Airport, found they had Parvovirus, a highly contagious virus which causes severe vomiting, diarrhoea and dehydration.

It usually affects unvaccinated dogs under six months old.

The puppies may have been imported from abroad to sell but were then abandoned when they became sick, according to investigating RSPCA inspector Adam Jones.

He described it is as “very touch and go” for the surviving puppies, a male and a female, who are now on fluids and medication but it is hoped they will pull through.

Mr Jones said: “They are microchipped with a Hungarian chip which isn’t registered in this country so it could be that they have been imported from abroad to sell on but have been abandoned when they became poorly.

“It would appear that these pups are the victims of the cruel puppy trade and we are keen to find out what happened to them.”

Anyone who has information is asked to call the RSPCA inspectorate appeal line on 0300 123 8018.