Sleuthing Cracked Salmonella Case
Nashua — How did health officials figure out that the salmonella bacteria which hospitalized more than a dozen people around Nashua and Concord this summer all came from the same source — dehydrated chicken sold as dog treats?
Science, teamwork and questions. Lots of questions.
“We have a questionnaire we give to every salmonella case that we investigate. It asks about 30 food items,” said Beth Daly, chief of infectious disease surveillance for the New Hampshire Department of Health and Human Services.
“If we know that they are potentially part of a cluster of cases, we give them a much longer questionnaire — 12 pages, that asks about several hundred food items. And from there, once you have a hypothesis, you might need to administer a third questionnaire,” she said.
David Merrill of Nashua knows this first-hand.
“The city called me, a nurse I think. She asked me a series of questions like, where did I eat, and what foods did I have, did I buy anything from a farmer’s market, have I eaten lettuce, things of that nature,” said Merrill. “Lots of questions.”
Merrill, 76, was hospitalized for five days in late August with salmonellosis caused by bacteria he picked up on his hands while handling Joey’s Jerky treats, dehydrated chicken meat. He had bought the product for more than two months and fed it to the family’s two Havanese dogs, Mulligan and Patches.
“I feed the dogs treats — when my daughter isn’t looking,” joked the retired software developer, who has fully recovered.
The treats were voluntarily recalled Tuesday by their maker, an in-home company called Kritter’s Kitchen Kreations in Loudon, after state health officials found that 21 people who became sick from salmonella had all bought the product. More than half of those people were hospitalized.
Tests confirmed Wednesday that the treats was the source of the salmonella. Dogs are less susceptible to salmonella than people; a few dogs in the households became sick, although it’s unknown if that was due to salmonella.
The treats are made of chicken bought from a grocery store and then prepared in a commercial dehydrator.
“The most likely reason is that the jerky was under-processed, the dehydrator didn’t kill the bacteria,” said Beth Daly, chief of infectious disease surveillance for the New Hampshire Department of Health and Human Services.
Salmonella is a bacteria that can cause intestinal sickness and, in rare cases, death — although there hasn’t been a salmonella-related death in New Hampshire for decades. People most commonly encounter salmonella on food that hasn’t been properly prepared: In 2009, for example, more than 50 students at a summer camp in Madison got sick because a mixer used to prepare pudding wasn’t completely cleaned between meals.
Salmonellosis, the disease caused by the bacteria, is reportable, meaning doctors, hospitals and other health-care providers must alert the state health department when they diagnose a patient. A “couple hundred” cases are reported each year in New Hampshire, Daly said.
Usually, doctors also send a stool sample to the state health laboratory for analysis of the bacteria.
“Our lab does genetic testing to find out if any patients have the same strain (of bacteria),” Daly explained. Salmonellosis is usually “sporadic,” with “people just getting it in their home from chicken, or something like that.”
In this instance, cases started being reported as early as June and officials suspected they had a single cause. Because this is a common strain of salmonella, samples were sent to the national Centers for Disease Control for a second type of test.
“They confirmed it was related; we got word back Aug. 28,” Daly said.
Public health nurses and other health officials for the state and the Nashua Health Department began contacting patients, looking for a common link. That isn’t easy.
“People have a lot of overlapping exposure – we ask about chicken, eggs, lettuce ... and look at a whole week time frame,” Daly said.
“We did re-interviews, and noticed that they were all dog owners, so we started asking questions about what kind of pet foods and pet treats they had.”
“It’s always nice when you solve one. In this case, we did it quickly,” she added.