Researchers at South Dakota State University’s Animal Disease Research and Diagnostic Laboratory were puzzled.
Two kids—an infant and a teenager—from two different families had been diagnosed with a salmonella infection. Calls about salmonella infections aren’t uncommon, but this particular situation was unique.
“This all started with a call from the South Dakota Department of Health,” said Russ Daly, an SDSU Extension veterinarian and the state public health veterinarian. “They keep track of these infections in people, and this started with couple of illnesses. They identified an unusual strain of salmonella.”
“It was an unusual strain of salmonella that you usually never see infecting people,” said Joy Scaria, an associate professor in the Department of Biomedical Sciences and the faculty in charge of the food safety section in ADRDL.
The suspected strain was known as salmonella bongori and can causes the infected person to fall ill with a fever, abdominal pain, nausea, diarrhea and vomiting. When cases of salmonella—either as outbreaks or single illnesses—occur, they can often be traced back to contaminated food or drinks. Once a salmonella outbreak is confirmed, the Department of Health will get a call and begin an investigation into the cause. If officials determine that food or drink isn’t the culprit, they will look for other factors, like animals in the household or that may have come in contact with the patient.
“It was a peculiar case,” Scaria said. “After the Department of Health interviewed the families, it was discovered that they both had pets in the house.”
Salmonella bongori is a unique strain commonly associated with reptiles. The name “bongori” is derived from the city of Bongor, Chad, after the strain was discovered in a lizard there in 1966.
What did both of these families, who lived on opposite sides of the state, have as pets?
As the state public health vet, Daly was called in to get some samples from each of the reptiles to see if the salmonella infection was the same in the people and in the animals.
"Was it just coincidence they had bearded dragons, or were they really the source?” Daly said. “We knew reptiles as pets can be sources of salmonella.”
Daly immediately turned to the “salmonella experts” at the ADRDL for help. He took a group of SDSU students to one family’s home to collect the samples. Samples were also obtained from the family on the other side of the state, and they began to “fingerprint” the reptiles’ samples so they could be matched up with the human isolates.
“They cultured the same darn bacteria in the bearded dragons that they saw in the humans,” Daly said. “We knew right away that their infections didn’t come from some other source. They came from contact with the animals.”
“That sort of confirmed the Department of Health’s suspicion that these pets were the source of infection,” Scaria said.
Scaria continued with genomic testing, comparing the bacteria he found with all the known cases of salmonella bongori. The Food and Drug Administration funded the genomic testing as the ADRDL serves as a whole genome sequencing lab for the FDA’s Veterinary Laboratory Investigation and Response Network.
“What we found was the salmonella bongori that we isolated from the pets and the kids were 100% identical,” Scaria said.
Scaria was confident in the diagnosis after comparing a similar case of salmonella found in an Ohio lab in 2015. In that case, a bearded dragon was also sick with salmonella bongori, which means this strain was likely circulating in bearded dragons around the U.S. More than likely, the bearded dragons all came from the same breeding facility that is supplying the reptiles to pet stores.
The kids were able to make a full recovery, and the bearded dragons, despite having the infection, were fairly healthy.
“If a susceptible person is exposed, it can make the person sick,” Scaria said. “Kids don’t have their immune systems fully developed, and bongori, for some reason, can cause infection.”
According to Daly, the bearded dragons were fine and not exhibiting any symptoms of the infection.
“The bearded dragons are an interesting pet as they don’t always have a veterinarian looking after them,” Daly said. “These bearded dragons were healthy, so there wasn’t really any reason for them go to a vet.”
For Scaria, this situation highlighted the importance of surveillance on both the animal and human side.
“If the Ohio lab didn’t test back in 2015, we wouldn’t have been able to trace it back to that strain of bongori,” Scaria explained.
Further, young children and people over the age of 65 should be cautious when handling and keeping these pets as they are more at risk for infection, Scaria said.
For Daly, the situation served as a learning experience for both himself and the students. It also highlighted the unique and impactful nature of having the state diagnostic lab on SDSU’s campus.
“Other states have their lab in the state capital or in their Department of Agriculture,” Daly explained. “The beauty of having the lab here at the university is that there are so many chances for good, good synergy here.
“We are really blessed here because our lab has constant good communication with the Department of Health and the Animal Industry Board,” Daly added. “We really work together well in this state.”