A new study from Penn State researchers has identified household dogs as an overlooked source of antibiotic-resistant Salmonella transmission to humans. The research, published in Zoonoses and Public Health, examined the spread of nontyphoidal Salmonella between dogs and their human companions.
The study analyzed data from the U.S. Food & Drug Administration’s Veterinary Laboratory Investigation and Response Network, identifying 87 cases of nontyphoidal Salmonella in domestic dogs between May 2017 and March 2023. Researchers matched these cases with human infection data from the National Center for Biotechnology Information database, discovering 77 suspected cases of zoonotic transmission involving 164 strains across 17 states.
Lead researcher Dr. Erika Ganda, assistant professor of food animal microbiomes at Penn State College of Agricultural Sciences, said that Salmonella infections in dogs can present with or without symptoms. The study found that dogs can carry and transmit the bacteria while appearing completely healthy, creating potential risks in household settings where close human-dog interaction is common.
The research team identified 16 nontyphoidal Salmonella isolates from humans that were closely related to six dog-associated strains. All identified strains contained antimicrobial resistance genes for drug classes categorized as critically or highly important by the World Health Organization, raising concerns about treatment effectiveness.
Sophia Kenney, a doctoral student in molecular, cellular, and integrative biosciences who led the study, stressed the importance of considering companion animals in disease transmission. The research highlights the need for a “One Health” framework that recognizes the interconnected nature of human, animal, and environmental health in addressing antimicrobial resistance.
The Centers for Disease Control and Prevention (CDC) reports that Salmonella transmission typically occurs through contaminated food consumption or contact with infected individuals or animals. The bacteria can spread through accidental exposure to feces, often via hand-to-mouth contact or interaction with pets. Symptoms of nontyphoidal Salmonella infection include diarrhea, fever, and abdominal cramps, with some cases progressing to severe complications.
Dr. Nkuchia M’ikanatha, lead epidemiologist for the Pennsylvania Department of Health and study co-author, referenced a recent outbreak that illustrates the research findings. A multi-state incident linked to pig ear pet treats resulted in 154 human infections with multidrug-resistant Salmonella across 34 states, demonstrating the real-world implications of the study’s findings regarding pet-related transmission.
The significance of the research is amplified by current pet ownership statistics. Over half of U.S. homes include dogs, creating numerous potential transmission pathways. The close physical interaction between humans and dogs, including activities such as face licking and bed sharing, increases the risk of bacterial spread.
The study’s findings emphasize the critical role of antimicrobial stewardship in veterinary medicine for companion animals. Researchers stress that proper surveillance must extend beyond traditional agricultural and human medical settings to include household pets as potential transmission vectors.
Historical context adds another dimension to the research. Evidence suggests Salmonella has evolved alongside human civilization for approximately 10,000 years, coinciding with the domestication of animals. This long-standing relationship between humans, animals, and the bacteria underscores the persistent nature of the public health challenge.
The research team’s analysis revealed diverse serotypes among the isolated strains, with most having clinical relevance to human health. While the available datasets did not include information about infection severity or treatment outcomes, the presence of antimicrobial resistance genes in all identified strains presents a significant concern for public health officials.
Dr. Ganda noted that bacterial interactions with human and animal health exist on a spectrum, with some bacteria being beneficial while others pose health risks. The research aims to improve understanding of these relationships to better manage potential health threats while maintaining the benefits of pet ownership.
The study suggests several preventive measures to reduce transmission risk. Basic hygiene practices, particularly regular hand washing, remain crucial for preventing bacterial spread between pets and humans. Proper food handling and awareness of pet treat contamination risks are also important factors in prevention.
Recent years have seen multiple instances of pet-related Salmonella outbreaks, further emphasizing the need for increased awareness and preventive measures. These cases often involve contaminated pet foods or treats, demonstrating the various pathways through which household pets can become sources of bacterial transmission.
The research contributes to a growing body of evidence supporting the need for comprehensive approaches to antimicrobial resistance and disease prevention. By identifying household dogs as potential vectors for antibiotic-resistant Salmonella, the study helps fill a gap in understanding transmission pathways and supports more effective public health strategies.
Commenting on this article, the nation’s leading Salmonella lawyer said, “By understanding the potential risks of Salmonella infections from dogs, pet owners should be able to maintain safe and healthy relationships with their furry companions while minimizing transmission risks.”
