They had taken multiple rounds of drugs, professionally deep cleaned their home and replaced contaminated toothbrushes, but none of it worked for long. Inevitably, the infection came roaring back.
“It seemed like the whole family was on antibiotics, had just stopped taking antibiotics or was coming down with strep again,” recalled Levitis, an evolutionary biologist who at the time was an associate scientist at the University of Wisconsin.
That New Year’s Day, rapid tests showed that Iris and all three children had strep; Levitis did not. Three weeks earlier Iris and two of the children were found to be infected. And two weeks following the New Year’s visit, after everyone had taken a full course of antibiotics, two of the children tested positive.
Over the next three months, which included several more bouts of strep, Levitis began to suspect that the cause of the repeated infection was in their home. But finding medical professionals who took his controversial hypothesis seriously proved to be a challenge.
After a search, Levitis managed to find a receptive audience. And once the possible source of recurrent strep was treated, the round robin infection stopped.
The first case occurred in late October 2017. Levitis was in Massachusetts on a research trip when his wife called to tell him that she and all three of their kids — Tigerlily, then 6, Kestrel, who was 3, and 14-month-old Peregrine — had tested positive for strep and were taking antibiotics.
Levitis, who had been battling a sore throat since leaving Madison several days earlier, called his doctor and was given a prescription for an antibiotic. Because the rest of his family was infected, he, too, was presumed to have strep.
After a round of antibiotics, everyone seemed to recover.
But five weeks later, his daughters complained of sore throats. This time the entire family was tested. Throat cultures revealed that all five had strep.
Within a few days the infection seemed to have cleared. But success was short-lived; the New Year’s Day visit occurred three weeks later. This time the doctor prescribed a different antibiotic.
Levitis said that he and his wife were reminded of the need to finish the full course of antibiotics and of sanitation measures they had been following, including replacing the toothbrushes they had been using.
But two weeks later, on Jan. 16, Kestrel and Tigerlily had strep again. And at the end of January, all three kids tested positive.
“We were so done with this and painfully aware that something was wrong,” Levitis recalled. Nobody at school or day care was getting strep, he said, so he suspected that something in their house was the source
Four months before the first outbreak, the family had adopted Umberto, a 3-year-old gray cat, from a nearby family.
“I started looking at the scientific literature, and everything said that cats can’t transmit strep,” Levitis recalled.
Levitis said his wife asked their doctors about the possibility that cats could be vectors of strep, while he queried his cousin, a veterinarian.
“They all pretty much said the same thing: ‘There’s no evidence that cats can transmit strep to humans, but if you want to be safe, get rid of the cat,’ ” Levitis recalled.
That seemed unthinkable; they all adored Umberto. “He’s so loving and patient with our kids and such a wonderful pet,” Levitis said. “And we didn’t know for sure that he was the culprit.”
Although there are diseases that cats can transmit to people — including toxoplasmosis, cat scratch disease and ringworm — Streptococcus A, the bacteria that causes strep throat, is not believed to be among them.
A 2002 report from the American Veterinary Medical Association noted that while doctors sometimes blame pet cats and dogs for recurrent strep throat in children “evidence doesn’t support this.”
“There is more evidence that pets carry group A Strep[tococcus] temporarily and only when in contact with an infected person,” a former association president concluded. “So, tell your kids with Strep[tococcus] not to kiss the kitty.”
Cats and dogs can infect humans with a strain called strep canis, which is present in animal saliva and is usually transmitted through a bite.
Iris Levitis asked their vet whether she could test Umberto for strep in case he was a conduit. The vet refused: Umberto seemed healthy and there was no reason to swab the throat of a healthy cat, which would require hooking him up to oxygen and administering general anesthesia.
A tantalizing case
As a scientist, Levitis said he was frustrated that no one seemed willing to consider the possibility that in rare cases a cat might harbor strep that could be transmitted to humans. A few published reports had suggested such a scenario.
Among them is a 2007 letter in the Mayo Clinic Proceedings by a Pennsylvania internist who described an experience similar to the Levitis family. His three young children developed recurrent strep, which was eradicated after they — and their cat — were treated simultaneously with antibiotics.
The Levitises called a few veterinary practices to see if they’d test Umberto; all said no.
“We thought about dosing him ourselves,” Levitis recalled, but “decided it was a bad idea.”
In early March, 3-year-old Kestrel got strep throat along with respiratory syncytial virus, which led to pneumonia, resulting in a two-day hospitalization. After she got home, the couple was discussing the plethora of medical resources available in Madison, which includes a large and respected college of veterinary medicine.
“Iris had the brilliant idea” of calling the university animal hospital and trying to talk to an expert there, Levitis recalled. Maybe, the couple thought, an academic center would be more receptive to the cat hypothesis than community vets had been.
She wound up talking to Caitlin Barry-Heffernan, a fourth-year veterinary internal medicine resident. Then she handed the phone to her husband for his pitch.
“I talked about it as a research case,” Levitis said, “not a guy who got strep throat from his cat.”
An unusual throat culture
“We were all kind of skeptical,” recalled Barry-Heffernan, who now practices in Southfield, Mich., outside Detroit. It is uncommon, she said, for cats to carry strep A, because the bacteria “doesn’t like to live on animals.”
But she was intrigued by the possibility and persuaded by Levitis. He was scientifically knowledgeable and “it was a pretty believable circumstance.”
Barry-Heffernan said she walked down the hall to consult with a veteran microbiologist. “She was very skeptical,” Barry-Heffernan recalled, but agreed that “we should be able to culture it if it’s there.”
So Barry-Heffernan told Levitis to bring his cat in for a throat culture.
On April 4, while the entire family was taking antibiotics for the seventh bout of strep in as many months, Umberto was seen by Barry-Heffernan and a vet student. They whisked Umberto, who Barry-Heffernan said seemed “perfectly healthy,” into a nearby room and quickly swabbed his throat. Neither anesthesia nor oxygen was required.
“Umberto was a really nice cat,” she recalled, so the procedure wasn’t difficult.
To the surprise of the vet school faculty, group A strep was found in the cat’s throat; it appeared to match the strain of strep collected during Levitis’s most recent throat culture.
“Almost certainly Umberto was contributing to the family’s infections,” Barry-Heffernan said. She prescribed antibiotics for the cat and a disinfectant spray for his fur. And the Levitis family was given another round of antibiotics.
Soon afterward they left on a previously scheduled two-week trip to Costa Rica. In their absence Umberto was given his medication, and the house was professionally cleaned for a second time.
Since then, Levitis said, no one has had strep.
“Once we identified Umberto as a carrier, it was really easy to address,” Barry-Heffernan said. It seems likely that the infection was being passed among the asymptomatic cat and various members of the family; it probably originated in a human. (Similarly, the small number of cats and dogs known to have tested positive for the novel coronavirus are believed to have been infected by people; there is no evidence animals can transmit the virus to humans.)
Barry-Heffernan said she hopes that the Levitises’ unusual case doesn’t cause people to get rid of their pets. “It was very easily treated,” she noted.
Levitis, who now lives in Northern California with his family — and Umberto — said he is convinced that treating the cat eradicated the infection that had bedeviled his family.
“We got lucky,” he said, “because Caitlin had an open mind.”
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