2016-2017 Salmonella Heidelberg Investigation

The Wisconsin Department of Health Services, along with the Centers for Disease Control and Prevention (CDC), United States Department of Agriculture (USDA), Wisconsin State Laboratory of Hygiene (WSLH), Wisconsin Veterinary Diagnostic Laboratory (WVDL), Wisconsin Department of Agriculture, Trade and Consumer Protection and other state health departments is investigating an outbreak of multi-drug resistant (MDR) Salmonella Heidelberg infections.

Salmonella Heidelberg Case Count -2016
Updated December 3,2016
Wisconsin Cases 12
Nationwide Cases (including Wisconsin cases) 21

Epidemiological, traceback, and laboratory findings have identified contact with dairy bull calves purchased in Wisconsin as the likely source of most infections.

Eight ill people were hospitalized, and no deaths have been reported. In Wisconsin, investigators have identified 12 people living in eight counties who tested positive for the outbreak strain of MDR Salmonella Heidelberg.

Among the Wisconsin patients, more than 90% had direct or indirect contact with dairy bull calves. More than half the illnesses occurred in children under 10 years of age. During 2015-2016, WVDL has also isolated the outbreak strains of MDR Salmonella from calves, primarily from Wisconsin, but also from several other states.

Molecular sub-typing of human and cattle MDR Salmonella Heidelberg isolates at WSLH and Centers for Disease Control and Prevention (CDC) showed that they were highly genetically related to one another, or the same strain. Standard antibiotic resistance testing conducted by the WSLH and CDC showed this strain of Salmonella Heidelberg is resistant to antibiotics normally used to treat severe Salmonella infections, including ampicillin, trimethoprim-sulfamethoxazole, and ceftriaxone.

Although treatment options are limited, infections caused by this strain of Salmonella have been successfully treated. This highlights the importance of providers requesting antimicrobial susceptibility testing when treatment for Salmonella is indicated.

Last Revised: December 13, 2016