OK, it’s safe to buy pig ears for the dog again.

Except for pig ears on a recall list, the federal Centers for Disease Control and Prevention and the Food and Drug Administration on Wednesday withdrew their previous warnings to avoid buying or feeding pets any pig ear treats.

The CDC reports the outbreak of multidrug-resistant Salmonella infections from contact with pig ear treats is over.

The outbreak doubled and tripled in size, reaching 34 states before it ran its source. The July 4th weekend was not yet underway when the CDC first announced that pig ears were responsible for 45 multidrug-resistant Salmonella infections 13 states.

The outbreak ends after having infected 154 people with the multidrug-resistant strain of Salmonella. Information on 133 who were treated shows 35, or 26 percent, required hospitalization. There were no deaths.

Almost 20 percent of those infected were children younger than 5. Children were likely infected from contact with a pet with a pig ear treat.

In its final investigative notice, CDC again advised the public not to feed or contact any pig ears under recall. It also reminded people to always wash their hands before and after feeding any pig ears to dogs.

The CDC said epidemiologic, laboratory, and traceback evidence all points to pig ears from “many different suppliers” as the likely source of the outbreak.

The FDA Center for Veterinary Medicine investigated the multistate outbreak of multidrug-resistant human Salmonella infections linked to contact with pig ear pet treats. Salmonella strains included Cerro, Derby, London, Infantis, Newport, Rissen, and I 4,[5],12:i:-.

Public health investigators used the PulseNet system to identify illnesses that may have been part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting is performed on Salmonella bacteria isolated from ill people by using a standardized laboratory and data analysis method called whole genome sequencing (WGS).

The CDC’s PulseNet manages a national database of these sequences that are used to identify possible outbreaks. WGS gives investigators detailed information about the bacteria causing illness. In this investigation, WGS showed that bacteria isolated from ill people were closely related genetically. This means that people in this outbreak were more likely to share a common source of infection.

Whole genome sequencing (WGS) was conducted to identify any predicted antibiotic resistance in 110 isolates from ill people and 102 isolates from pig ear treat samples.

A total of 164 isolates had predicted antibiotic resistance or decreased susceptibility to one or more of the following antibiotics: amoxicillin-clavulanic acid (<1% of 164 isolates), ampicillin (53%), azithromycin (<1%), cefoxitin (<1%), ceftriaxone (<1%), chloramphenicol (33%), ciprofloxacin (50%), fosfomycin (2%), gentamicin (27%), kanamycin (2%), nalidixic acid (26%), streptomycin (33%), sulfisoxazole (30%), tetracycline (58%), and trimethoprim-sulfamethoxazole (27%). No antibiotic resistance was predicted for 48 (23%) isolates.

Testing of 13 clinical isolates using standard antibiotic susceptibility testing methods by CDC’s National Antimicrobial Resistance Monitoring System (NARMS) laboratory provided comparable results (fosfomycin and kanamycin were not tested by this method). If antibiotics were needed, infections related to this outbreak may have been difficult to treat with some commonly recommended antibiotics, and may have required a different antibiotic choice.

Investigation of the Outbreak
In interviews, ill people answered questions about a variety of exposures, including animal and pet food contact in the week before they became ill.

Of 128 ill people, 107 (84 percent) reported contact with a dog before getting sick. Of 94 people with available information, 62 (66 percent) reported contact with pig ear treats or with dogs who were fed pig ear treats. Both of these proportions were significantly higher than the results from a survey pdf icon[PDF – 787 KB] of healthy people who reported contact with dogs (61%) or handling dog treats (16%), such as pig ear treats, in the week before the interview.

Testing of pig ear treats identified the outbreak strains of Salmonella in 135 samples. Some of the pig ear treats were imported from Argentina, Brazil, and Colombia.

Some product labels indicated that the pig ear treats were irradiated. When properly conducted, the irradiation process should kill any Salmonella present on the pig ear treats. Finding Salmonella in products labeled as irradiated indicate they may not have been irradiated, they were not effectively irradiated, or there was another issue that caused Salmonella contamination.

FDA continues to investigate the manufacturing process and has posted answersexternal icon to frequently asked questions from members of the pig ear pet supply chain (manufacturers, suppliers, importers, distributors, retailers) regarding Salmonella control in these products.

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