Antibiotic Use for Companion Animal Treatments

A common concern for us at Hemopet is the growing resistance of microbes to antimicrobials such as antibiotics, antivirals, antifungals, and antiparasitics. Another concern of ours is whether the appropriate available diagnostic tools are utilized to confirm a suspected diagnosis before treatment is started. These two concerns do intersect.

Why? For example, fungal infections such as Valley Fever or Blastomycosis are usually initially suspected as bacterial or viral infections because of their symptom presentation. However, one would not know if it is bacterial, viral or fungal without relevant testing.

Let’s say you or your companion dog has Valley Fever, but it was misdiagnosed as a bacterial infection without testing. The selected antibiotic may work on some of the symptoms if there is a secondary bacterial infection because of a weakened or dysfunctional immune system due to the fungal infection. Consequently, the prescribed antibiotic will not do you or your dog any good, and symptoms very likely will proceed and worsen.

Thus, you have disease progression, as well as a reduction of harmless or beneficial bacteria in your body because of the antibiotic use. Antibiotics not only attack harmful bacterial, but also can impair good bacteria. The beneficial bacteria that remain, quickly adapt to resist the antibiotic and even can alert future invasive, harmful bacteria about this antibiotic. Thereby, promoting antibiotic resistance.

Further, antibiotics enable gastrointestinal dysbiosis due to their so-called “scorched earth” effect on the gut. Study after study from the renowned Texas A&M University’s Department of Small Animal Clinical Sciences Gastrointestinal Laboratory have indicated that dysbiosis can continue for a minimum of four weeks after antibiotic administration has been stopped.

Current Protocols to Combat Antimicrobial Resistance

Human medical care is beginning to benefit from established processes and procedures that measure the prevalence and appropriateness of antibiotic and antifungal use to combat antimicrobial resistance at the federal level.

In fact, there is a task force co-chaired by the Secretaries of the United States Departments of Health and Human Services (HHS), Agriculture (USDA), and Defense (DOD), as well as involvement from several other agencies.

The task force has identified veterinarians as integral to fighting antimicrobial resistance.

One of the objectives of the task force is to “evaluate data on antibiotic use and stewardship practices in production animal species, including cattle, swine, poultry, goats, and sheep.” This is critically important to human health because antibiotic-resistant bacteria can be passed up the food chain.

Indeed, some success already has been realized. The Food and Drug Administration (FDA) reported a 38% decline between 2015 and 2018 of medically important antibiotics sold for use in food-producing animals.

Yet, companion animals have not received the same attention and probably never will by this task force.

Thankfully, others like the American Veterinary Medical Association are taking charge of monitoring the prevalence of companion animal antibiotic prescriptions.

Companion Animal Antibiotic Use Studies

One example is the University of Minnesota College of Veterinary Medicine, which spearheaded two major projects to identify antibiotic distribution and use to companion animals in 2020.

These studies dissected the numbers from various medically important angles. For the purposes of our post, we will be simplifying here.

Small Animal and Equine Practices

Released in 2022, the first study evaluated 19 small animal and equine veterinary practices in Minnesota and North Dakota. Each of the practices submitted data for one day per quarter in 2020. To ensure the data were consistent, the practices could choose a day within a defined time period.

Small animal and equine practice results:

  • Total consults of dogs, cats and horses = 1,899
  • 489 patients prescribed at least one antibiotic (approximately one-quarter of total consults)
  • 216 patients out of the 489 prescribed at least one antibiotic had cytology or histopathology performed (44.2%)
  • 19 patients out of the 489 had bacterial culture and antimicrobial susceptibility testing (AST) performed (3.9%)
  • Antibiotics prescribed for conditions concerning these areas: skin (24.4%), ear (22.1%), eye (9.4%), gastrointestinal (8.3%), respiratory (8.3%), and urinary tract (7.6%)

This study cited other studies that noted cost was considered a barrier for diagnostic testing by veterinarians and companion pet parents alike. The reason why cytology is frequently used is because less expensive in-house cytology is available to veterinary practices, whereas bacterial cultures and AST need to be sent to a reference laboratory.

As an aside, many of our readers have not heard of this use of the acronym, AST. AST identifies the treatment that would be most effective against a particular infection.

With this study, we wonder how many of the total consults had a diagnostic test performed because we only know the testing done based upon the prescription rate.

Veterinary Teaching Hospitals

In the second study released in 2023, University of Minnesota worked with 14 other veterinary teaching hospitals (VTHs) from all regions of the country to figure out the prevalence of antibiotic use at their facilities. They measured one day of companion dog or cat care in August of 2020. The departments of primary care, internal medicine, surgery, emergency and critical care, and urgent care were included, but specialty clinics such as dermatology, oncology and dentistry were excluded.

VTH results:

  • Total dogs and cats = 883
  • 522 had at least one type of diagnostic test performed (59.1%).
  • 322 were prescribed at least one antibiotic on the study day or day before (36.5%).
  • 246/322 dogs and cats prescribed at least one antibiotic were tested (77%).
  • 274/561 dogs and cats not prescribed any antibiotics were tested (48.8%).
  • Of the 205 dogs and cats prescribed at least one antibiotic for treatment of infection: 79 (38.5%) had bacterial culture and AST, 67 (32.7%) had a urinalysis, and 52 (25.4%) had cytology conducted for the condition for which the antibiotic was prescribed.
  • Of the 64.5% (285/442) of antibiotics prescribed for systemic administration intended for infection treatment: 28.1% (80/285) were prescribed for confirmed infections, 61.1% (174/285) for suspected infections, and 10.9% (31/285) when no evidence of infection was recorded in the medical record.
  • The remaining antibiotic prescriptions were for prophylactic reasons (i.e., surgery) and nonantimicrobial effects.

The VTH results may appear better than the practices, but the two are really not comparable. Many dogs and cats are referred to VTHs by conventional practices, whereas specialty clinics were not included, and most importantly VTHs have reference microbiology laboratories on site. Indeed, the study authors point out that only 39% of dogs and cats prescribed at least one antibiotic had a bacterial culture and AST performed at the VTH.

Other areas noted that could be improved are:

  • Reviewing surgical protocols to reduce prophylactic prescriptions; and,
  • Ceasing prescriptions for non-antimicrobial effects.


Beaudoin, Amanda L et al. “Prevalence of antibiotic use for dogs and cats in United States veterinary teaching hospitals, August 2020.” Journal of veterinary internal medicine vol. 37,5 (2023): 1864-1875. doi:10.1111/jvim.16814,

Bollig, Emma R et al. “A quarterly Survey of antibiotic prescribing in small animal and equine practices-Minnesota and North Dakota, 2020.” Zoonoses and public health vol. 69,7 (2022): 864-874. doi:10.1111/zph.12979,

Pilla, Rachel et al. “Effects of metronidazole on the fecal microbiome and metabolome in healthy dogs.” Journal of veterinary internal medicine vol. 34,5 (2020): 1853-1866. doi:10.1111/jvim.15871,

Whittemore, Jacqueline C et al. “Effects of Synbiotics on the Fecal Microbiome and Metabolomic Profiles of Healthy Research Dogs Administered Antibiotics: A Randomized, Controlled Trial.” Frontiers in veterinary science vol. 8 665713. 26 May. 2021, doi:10.3389/fvets.2021.665713,

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