Antimicrobial-resistant pathogens affecting animal health

In this article:
  • Download the report: Antimicrobial-resistant pathogens affecting animal health in the U.S.
  • Find sharable, species-specific information on antimicrobial resistance.
  • Learn about actions that veterinary teams and others can take to combat antimicrobial resistance.

Antimicrobial-resistant pathogens affecting animal health in the U.S.

This report contains information and actions for veterinarians and others to maintain the effectiveness of antimicrobials approved for therapeutic use in animals.

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two hands with microscope

Antimicrobial use in animals, people, and the environment may contribute to antimicrobial resistance, which poses direct risks to animal health and welfare and can potentially impact human health.

The AVMA worked with microbiologists, epidemiologists, and species experts to identify bacteria affecting multiple animal species for which there is evidence of resistance to available antimicrobials. The resulting report, Antimicrobial-resistant pathogens affecting animal health in the U.S., can assist veterinary teams, producers, breeders, and animal owners with antimicrobial stewardship efforts.

Three people with stethoscopesAntimicrobial stewardship refers to actions taken to preserve the effectiveness and availability of antimicrobial drugs through responsible decision-making and conscientious oversight, while safeguarding animal, public, and environmental health.

Download this poster to share antimicrobial stewardship principles with your team. You can also download this checklist to help you implement antimicrobial stewardship in your practice.

Antimicrobial-resistant pathogens: A report

Maintaining the effectiveness of antimicrobials approved for therapeutic use in animals requires attention to stewardship across the One Health spectrum, especially among leaders in veterinary medicine, animal production, and public health. This report includes actions that veterinarians and our teams, producers, breeders, and others seeking medical care for animals can take to collaboratively combat antimicrobial resistance.

Only through concerted commitment and action will those caring for the health and welfare of animals succeed in maintaining the effectiveness of antimicrobials against bacterial pathogens.

The full report includes an overview of the impact of antimicrobial resistance on animal health in the U.S., report cards that summarize pathogens of concern for different host species, and a technical appendix.

Species report cards

These one-pagers, which are also included in the full report, provide basic information that supports antimicrobial stewardship for different host species. They are designed to be printed and posted in highly visible locations in veterinary practices and other facilities where animals are cared for. These summaries identify bacteria of particular risk, how to manage infections caused by them in the context of good stewardship, and their overall implications for animal health and welfare. For more information on specific pathogens, please reference the full report.

Dogs and cats

The prevalence of resistant bacteria in dogs and cats isn’t known, but those of concern include methicillin-resistant Staphylococcus (MRSA), as well as Pseudomonas and Campylobacter jejuni. Prior antimicrobial use is one risk factor for reduced effectiveness of subsequent antimicrobial therapy. Comprehensive healthcare plans and veterinary oversight of antimicrobial drug use in dogs and cats may help reduce antimicrobial resistance and maintain the effectiveness of critical therapeutic agents.



Bacteria responsible for endemic cattle diseases in the United States, such as bovine keratoconjunctivitis (IBK or “pink eye”) or bovine respiratory disease, are developing resistance to multiple available antibiotics. Difficult-to-treat infections have significant impacts on animal health and welfare, as well as long-lasting economic consequences for cattle producers. A key component of effective antimicrobial stewardship for cattle is disease prevention, which includes implementing good management practices and regular use of vaccines. More research is needed around strategies for disease prevention, control, and treatment in individual animals, as well as herd outbreaks.


Chickens and turkeys

The prevalence of E. coli and Pasteurella multocida infections increased substantively between 2018 and 2019. Identification of multi-drug resistance in these common pathogens calls for increased attention to biosecurity and environmental factors, such as water sanitation, rodent control, and ventilation.


Fish and shrimp

High mortality (up to 60% for Edwardsiella spp in catfish), combined with multi-drug resistance to the few FDA-approved antibiotics available to treat disease in fish and shrimp, harms animal health and welfare and can be economically devastating for aquaculture. Some antimicrobials used for aquatic species are sold over-the-counter and online to the public, including many that are prohibited or restricted for use in these species. Removing products that aren’t FDA-approved from the market and requiring veterinary oversight for those products that are approved may help reduce the development and spread of antimicrobial resistance. 



Some pathogens affecting equine health, such as Staphylocuccus spp and Pseudomonas aeruginosa, appear to be resistant to multiple antimicrobials. FDA-approved antimicrobials for horses are often not active against the resistant pathogens; legal, extralabel use of human and animal antimicrobial drugs may be necessary for treatment. Comprehensive attention to stewardship is important, including strategies for infection prevention and pathogen control, diagnostic testing to better inform therapeutic decisions, and prompt treatment and compliance with veterinarians’ recommendations.


Sheep and goats

Mastitis and abortions in these small ruminants are greatly impacted by antimicrobial-resistant pathogens. Staphylococcus spp and Campylobacter jejuni are the main pathogens of concern. Antimicrobial-resistant infections can be more difficult to treat and may only be recognized as non-responsive infections, leading to additional rounds of therapy with alternative antimicrobial drugs. Poor health has negative effects on animals’ welfare, and results in significant economic loss for producers by reducing both the quality and quantity of milk, meat, and fiber.



Resistance to antimicrobials has been identified for opportunistic, environmental, and commensal pathogens, such as Pasteurella, Streptococcus, E. coli, and Salmonella. Because these bacteria are ubiquitous in swine production, working with producers to consistently implement core principles of good swine health management is critical to prevent infections. These principles include not mixing pigs from different sources, adopting all-in/all-out management whenever practical, maintaining good hygiene, and minimizing environmental stresses due to temperature fluctuations and poor ventilation.


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Antimicrobial stewardship poster

The principles on this poster can be used to create antimicrobial stewardship plans in any veterinary practice setting. Use them to improve disease prevention strategies and antimicrobial drug prescribing, evaluate outcomes, and adjust plans accordingly.



Antimicrobial-resistant pathogen table

This resource provides a table of antimicrobial-resistant pathogens, the drugs to which there is evidence of resistance, and the species affected. Use this in tandem with the full report on antimicrobial-resistant pathogens affecting animal health in the U.S.