NEW BEDFORD — What’s the matter with Penny?

That’s the question that has been eating at Melissa Lawrence of New Bedford for more than a month.

She showed a visitor a video on her smartphone. In it, her 3-year-old mixed breed terrier is going crazy trying to play with the family cat, who looks deeply annoyed. “She’s a maniac,” Lawrence said.

The terrier, Penny, hasn’t been herself for more than a month. She was stricken suddenly with some sort of infection or poisoning, but in the weeks that Penny has been suffering no one has come up with an explanation, except perhaps the dog food voluntary recall in February that swept most of the food off the shelves.

Lawrence says she would buy Penny some Gravy Train canned dog food “twice a week,” she said. But about three or four weeks ago, Lawrence went to the store for the Gravy Train she always fed Penny.

But the shelves were empty not only of Gravy Train but also other brands produced by J. M. Smucker, such as Kibbles & Bits, Ol’ Roy and Skippy.

There are dozens more that were pulled of the shelf when it was discovered that pentobarbital, a euthanasia drug, had somehow made it its way into pet food. One supplier of animal fat and by products had somehow introduced the drug via animal fat, coming from one plant that Smucker later identified.

Meanwhile Penny struggled on. “She can’t even jump up on the couch,” Lawrence said. Penny now moves slowly, as if she is in pain, especially her hindquarters.

Penny spends a lot of time on a couch cushion, eating little if at all, and slowly losing weight, said Lawrence. She has had multiple veterinarian visits, but nothing has really worked to restore Penny to the joyful dog she had been.

Penny’s vet would not talk with a reporter despite having gotten permission from Lawrence.

At home, Penny’s visitors have included animal control officer Manny Maciel; Lawrence knows Maciel from her time volunteering in animal rescue, but has come to no conclusion about what might be happening to Penny.

All of the tests so far have turned up nothing, too.

Lawrence said that Penny is taking antibiotics, but there is only small improvement. She has a few weeks left of the medication, and Lawrence is hoping that her dog will improve.

The question arises: Are there other local dogs that have suffered with this? The Standard-Times contacted dog groomers, veterinarians and pet supply stores and came up empty. No one had any knowledge of other afflicted animals.

Recalls of pet food, meanwhile, are common. Peter Renaghan II, owner and manager of Denise’s Pet Care Center in Mattapoisett, said that recalls often involve minor things “like forgetting to add a drop of vitamin D,” he said. He said that there are “five a week” recalls, though his shop had only one brand that was affected by this one.

The pentobarbital, meanwhile, as potent as it is, is only detected in trace amounts in the dog food brands, said the FDA.

Lawrence is running out of options, but as of now she will not contemplate putting Penny down. Asked what Lawrence will do if the antibiotic fails, she said, “I hope it doesn’t involve burying her.” She said she will follow a vet’s advice, however.

There have been enough dogs poisoned by the drug that several class action lawsuits have been followed in California and New York. In the case of a California woman, three of her dour dogs died within minutes of ingesting tainted food, and a fourth turned gravely ill. Lawrence is looking for an opportunity to join a lawsuit.

Follow Steve Urbon on Twitter@SteveUrbonSCT.