93 Salmonella cases likely caused by pig ear dog treats

CDC officials stated that the likely sources of the bacteria were pig ear dog treats. Officials have not identified a common supplier.

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(Andrea Gantz)
(Andrea Gantz)

Public health officials in the United States continue investigating 93 cases of Salmonella infection in humans, as of July 17, which pig ear dog treats may have caused. The U.S. Centers for Disease Control (CDC) announced that several varieties of Salmonella, including serotypes Infantis, London, and Newport, are involved in the infections.

CDC officials stated that the likely sources of the bacteria were pig ear dog treats. Officials have not identified a common supplier of pig ear dog treats. People in 27 states were involved in this Salmonella outbreak. Twenty people have been hospitalized.

Pig ear dog treats may have harbored Salmonella

On July 3, Pet Supplies Plus recalled bulk pig ear product distributed to all its locations by several different vendors due to the potential of Salmonella contamination related to this outbreak.

Map of reported Salmonella cases

Ninety percent of 70 Salmonella-infected humans reported recent contact with a dog before falling ill, during interviews with the health officials. Of 34 out of 49 people with available information, or 69%, had contact with pig ear dog treats or dogs that had recently eaten such treats. Reported Salmonella illnesses started on between October 1, 2018 and June 20.

Details on public health investigation of Salmonella outbreak

From CDC:

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health laboratories coordinated by CDC. DNA fingerprinting is performed on Salmonella bacteria isolated from ill people by using standardized laboratory and data analysis techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE. WGS showed that bacteria isolated from ill people were closely related genetically. This means that people in this outbreak are more likely to share a common source of infection.

Ill people range in age from less than 1 year to 90 years, with a median age of 38 years. Forty-three (46%) ill people are female. Of 67 ill people with information available, 20 (30%) have been hospitalized. No deaths have been reported.

Illnesses might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of 2 to 4 weeks. Please see the Timeline for Reporting Cases of Salmonella Infection for more details.

Whole genome sequencing analysis of Salmonella isolates from 33 ill people predicted antibiotic resistance or decreased susceptibility to ampicillin, ciprofloxacin, gentamicin, nalidixic acid, streptomycin, sulfisoxazole, and tetracycline. Testing of one clinical isolate using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) provided comparable results. If antibiotics are needed, infections related to this outbreak may be difficult to treat with some commonly recommended antibiotics, and may require a different antibiotic choice.

CDC investigation of the Salmonella outbreak

Epidemiologic, laboratory, and traceback evidence indicates that contact with pig ear dog treats is the likely source of this outbreak.

During the investigation, officials from the Michigan Department of Agriculture and Rural Development gathered pig ear dog treats at retail locations where ill people reported buying the products. They sampled pig ears for Salmonella. As additional strains of Salmonella were identified in pig ear products, a search of the CDC PulseNet database identified ill people infected with some of these strains, including Salmonella Infantis, Salmonella London, and Salmonella Newport. These ill people were added to the outbreak investigation.

On July 3, 2019, Pet Supplies Plus recalled bulk pig ears stocked in open bins because they might be contaminated with Salmonella. 

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