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2021 AAEP Convention Bonus Coverage: Gentamicin-Induced Auditory Loss in Horses

Coverage during the live 2021 AAEP Convention is brought to you by EquiManagement and is sponsored by ADM Cellarator Advantage.
ears horse closeup from above the eyes

Monica Aleman, MVZ Cert., PhD, DACVIM (Large Animal and Neurology and Neurosurgery), of the University of California, Davis, talked about Gentamicin-Induced Auditory Loss in Healthy Adult Horses at the 2021 AAEP Convention. 

Huh, Who’d Have Thunk?

Part Three: Reminiscing About the Good Ol’ Days

Because it has been so long since I’ve left the New York due to COVID, I spent a few minutes meandering about downtown Nashville. I remarked to myself how similar Nashville was to other cities hosting past AAEP Conventions. I got so caught up reminiscing about years gone by that my brain started blending—almost confusing—the past and the present.

The hustle, noise, lights and excitement of the Nashville strip ...

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... reminded me of Vegas in 2015:

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And the free electric scooters literally strewn throughout Nashville (below, left) reminded me of San Antonio in 2017. San Antonio was where I was first introduced to personal public transportation in the form of pay-per-use Segways along the River Walk:

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The holiday splendor in the Music City Center (below, left) reminded me of San Francisco in 2018:

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And, of course, I was reminded of the locale where I enjoyed the bulk of the virtual 2020 Annual Convention: 

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After leisurely making my way to MCC to enjoy this year’s keynote speaker Meagan Johnson, I was abruptly ripped back to the present. Johnson’s good-natured pokes at my generation combined with how I merrily strolled down memory lane this same morning highlighted one clear fact: I am old.

Old people ruminate about the good ol’ days. And as pointed out in Johnson’s address, old people still print e-mails and fax documents, prefer to make phone calls rather than text frantically with both thumbs, and judge young folks’ work ethic. Millennials and Gen Zers also think I am old.

Stung and numb with this revelation, I limped to my next session somewhat in a daze. Which, in retrospect, made me look like I was arthritic and confused about where I was and what I was supposed to be doing.

To make matters worse, I could not for the life of me remember learning any details about gentamicin-induced ototoxicity back in vet school.

In case you are in the same boat, let me share what I learned in the presentation by Monica Aleman, MVZ Cert, PhD, Dipl. ACIM (LAIM, Neurology) from the University of California-Davis, School of Veterinary Medicine, Department of Medicine and Epidemiology.

According to Aleman, gentamicin has nephrotoxic and ototoxic effects in various species. Anywhere from 2% to 40% of human patients develop ototoxicity either during therapy with gentamicin or days to weeks after.

Considering how commonly gentamicin is prescribed in equine practice, there is an alarming dearth of information regarding ototoxicity in this species. Aleman and colleagues therefore conducted an experiment to assess auditory loss in which 10 healthy horses were administered routine doses of intravenous gentamicin: 6.6 mg/kg once daily for 7 days.

Auditory function was assessed using brainstem auditory evoked response (BAER) at baseline, on day 7 (the last day of treatment), and again 30 days after the last dose of gentamicin.

By day 7, six of the 10 horses had auditory loss based on BAER. Four of those six horses recovered their hearing by day 37; however, one additional horse was newly diagnosed as deaf at that point in time (i.e., one horse developed auditory loss after cessation of treatment). In total, three of the 10 healthy horses treated with routine doses of gentamicin suffered irreversible auditory loss.

You heard that right. Three out of 10.

In her concluding remarks, Aleman relayed that sensorineural auditory loss is a potential risk associated with gentamicin. It can be partial, complete, uni- or bilateral, and is sometimes irreversible. Further, auditory loss can occur either during or after treatment. Despite these concerning findings, Aleman said she won’t stop using gentamicin when indicated.

“Amikacin is a very good antimicrobial—and cost effective. Just be sure to advise your clients about this potential side effect,” recommended Aleman.

Warn owners, too, that horses with auditory loss may be more easily startled. This, in turn, can decrease performance, negatively affect quality of life, and raises safety concerns because they are “spooky.”

Based on today’s events and musings, I feel forced to temporarily replaced my catchy phrase “Huh, who’d have thunk?” with “Say what, now?”

I am confident, however, that I will awaken tomorrow refreshed, rejuvenated, revitalized and ready to take on the world. I will have a spring in my step and blissfully forget I am old. I will again search for things that make me say “Huh, who’d have thunk?” with the frivolous abandon that only the young at heart possess. But first let me put in my teeth….  

About ADM Animal Nutrition and Cellarator Advantage

Demands of exercise are a stressor for the performance horse. Heavy work can overwhelm the body’s natural ability to deal with oxidative stress which can damage muscle proteins, lipids and DNA, release pro-inflammatory cytokines leading to muscle pain, and damage the mitochondrial membrane decreasing energy production. Cellarator Advantage RECOVERY+ by ADM Animal Nutrition™ was designed to help the performance horse combat the stress of exercise. To learn more, watch this video and come visit with the ADM experts at AAEP, booth #601/700.

ADM for AAEP Bonus Coverage Cellarator Advantage

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