1. Index Case
You have recently been hired as the public health veterinarian at the Minnesota Department of Health. It’s only your second week on the job, and you are assigned the following case:
A 5-year-old boy named Sam was ill for 14 days with severe diarrhea, stomach cramps, fever, and intermittent vomiting. Occasionally the diarrhea was bloody. When Sam’s mother took Sam to the doctor, the doctor treated Sam with oral fluids and gave Sam’s mother (Lucy) instructions to give Sam plenty of fluids. The doctor also told Sam’s mother to call back if there was any change in Sam’s condition. Upon returning home from the clinic, Lucy found that Sam’s pet mouse (Melvin) had died. The mouse had been suffering from diarrhea and lethargy since they bought it at a pet store a few days before. Lucy wondered if Sam’s illness and Melvin’s illness were related. She contacted Sam’s pediatrician and the pet store where she bought Melvin. Staff at both locations told her that it sounded like Sam’s illness and Melvin’s illness were a coincidence.
With Lucy’s encouragement, the pediatrician agreed to submit Sam’s stool specimen to a clinical laboratory. A couple days later, the clinical laboratory reported that the stool specimen yielded Salmonella. The clinical laboratory forwarded the Salmonella isolate to the Minnesota State Public Health Laboratory and reported the case to the Minnesota Department of Health. The Minnesota Department of Health attempts to interview all people with a laboratory-confirmed Salmonella infection. As part of this routine surveillance, you contact Sam’s mom to inquire about possible sources of infection. During the course of your conversation, Lucy wonders if Sam’s illness could be related to the recent death of Sam’s pet mouse. You share your knowledge of Salmonella epidemiology with Sam’s mother:
Non-typhoidal Salmonella includes common serotypes such as: S. Typhimurium, S. Enteritidis, and S. Newport. Most mammals, birds and reptiles are the reservoirs for non-typhoidal Salmonella. This means that most infections can ultimately be traced back to animals. The immediate source for human infections is usually food, but people can also become infected by direct ingestion of animal or human feces; usually by contaminating their hands and then putting their fingers in their mouths. Human salmonellosis usually causes self-limiting gastroenteritis, but can sometimes cause severe infections and even death, especially if the infection becomes systemic.