Horse Gut Problems Can Last a Month After Using Antibiotics, Study Finds

The way we use antibiotics is changing in the world of medicine, especially as we learn more about their impact on the inhabitants of the gut.

Ontario Veterinary College researcher Dr. Diego Gomez recently participated in a collaborative study with researchers across North America to study the effects of intravenous antimicrobials on the equine gut.

They collected fecal samples three, five and 30 days after administration of antimicrobials commonly used in veterinary practice, including ceftiofur, oxytetracycline and enrofloxacin.

What they found was that the bacterial population started to change by day three and in some horses, depending on the antimicrobial given, the changes can last for up to 30 days. Certain gut bacteria responsible for nutrient metabolism in hay and forage were shown to be further reduced from the third to the 30th day of the study.

The results suggest that the use of antimicrobials may predispose the horse to diarrhea, colitis or metabolic diseases by altering bacterial communities in the gut.

Gomez said that for future studies, sampling at 60 days would help track longer-term changes.

When using antibiotics, some clinicians have proposed the use of probiotics or prebiotics to minimize changes in bacterial populations after administration of antimicrobial drugs, but currently there is only anecdotal evidence rather only scientific evidence supporting their use, Gomez said.

In 2021, another study began looking at the impact of oral antibiotics. Gomez explained that early data analysis reveals that some antimicrobials produce major changes in gut bacterial communities while others do not, and therefore some antibiotics are more likely to cause diarrhea.

Gomez stressed the importance of seeking veterinary advice before administering antimicrobials to horses.

“We must be responsible when administering and deciding to administer antimicrobials to horses, not only because it may predispose the horse to disease, diarrhea in particular, but also because of the emergence of antimicrobial resistant bacteria which can lead to difficulties in treating the infection in horses, humans and horses.

Effects of intravenous antimicrobial drugs on the equine fecal microbiome. Liepman, RS; Swink, JM; Habing, GG; Boyaka, Pennsylvania; Caddey, B.; Costa, M.; Gomez, DE; Toribio, RE Animals 2022, 12, 1013.

» To learn more about preventing antimicrobial drug resistance, see the Canadian Animal Health Surveillance System (CAHSS) website.

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