Antibiotics offer no benefit in treating dogs with diarrhoea

Last Updated: 04 Oct 2023 19:00:35

A new VetCompass study from the Royal Veterinary College (RVC) has revealed that veterinary prescription of antibiotics at first presentation of uncomplicated diarrhoea in dogs causes no difference in clinical resolution of these cases. The study suggests that dogs with uncomplicated diarrhoea do not need antibiotics as part of their veterinary care plans. These findings will help veterinary surgeons provide the best care for their dog patients while also avoiding unnecessary use of antibiotics, and also ensure that owners know what to expect when seeking veterinary advice.

Diarrhoea is the sixth most common disorder affecting dogs annually in the UK. The condition can cause stress and discomfort for affected dogs and can be challenging for owners to manage. While antibiotics can be beneficial for some diarrhoea cases when there is a known bacterial infection or septicaemia, for decades antibiotics have been commonly prescribed even without evidence of a bacterial cause in the belief that they were helpful in uncomplicated diarrhoea cases too.

Until now, there has been limited research to show the value either way of antibiotics for treating uncomplicated diarrhoea. Over-use or inappropriate use of antibiotics in animals has been linked with rising levels of antibiotic resistance that is considered one of the most serious health-related problems worldwide. Therefore, evidence on the value of antibiotic use to treat diarrhoea in dogs is essential to support veterinary surgeons to achieve the best clinical management of diarrhoea whilst also contributing to global efforts on responsible antibiotic use.

Led by the RVC’s VetCompass Programme, this study is based on the anonymised clinical records from more than two million dogs under first opinion veterinary care in the UK in 2019. Clinical trials (namely randomised controlled trials) are considered "gold standard" for estimating causal treatment effects but are not always feasible or ethical. Therefore, this study used novel methods of causal inference "target trial emulation" to estimate real-world causal effects from veterinary electronic clinical records. Causal inference from large databases ("Big Data") can be viewed as an attempt to emulate (i.e., replicate) a randomised controlled trial - the target trial - to answer a question of interest that often cannot be answered in any other way.

The study included a random sample of 894 dogs aged between three months and 10 years old diagnosed with uncomplicated diarrhoea during 2019. Of these, 355 (39.7%) dogs were prescribed antibiotics, and 539 (60.3%) dogs were not prescribed antibiotics (with or without additional supportive treatment) at first presentation for diarrhoea. In the analysis, these dogs were balanced for a range of other differences between the groups including age, breed, body weight, insurance status, the presence of two or more medical conditions, vomiting, reduced appetite, blood in faeces, raised temperature, duration of diarrhoea, additional treatment prescription and veterinary group. This effectively meant that the only difference between the two groups was that one group received antibiotic treatment while the other did not.

The likelihood of clinical resolution of diarrhoea in the dogs prescribed antibiotics was 88.3%, compared with 87.9% in dogs not prescribed antibiotics. This tiny difference of 0.4% between the groups was not statistically significant, leading to the conclusion that antibiotic treatment did not cause any beneficial effects in the treatment of uncomplicated diarrhoea in dogs. Almost nine in 10 dogs with uncomplicated diarrhoea recovered after a single veterinary visit regardless of antibiotic treatment.

As an additional analysis, the study also explored gastrointestinal nutraceuticals (products derived from food sources that aim to restore digestive health such as probiotics and prebiotics) for treatment of uncomplicated diarrhoea in dogs. Gastrointestinal nutraceutical prescription (with or without other supportive treatment) at first presentation of uncomplicated diarrhoea caused no statistically significant difference in clinical resolution compared to dogs not prescribed gastrointestinal nutraceuticals.

Camilla Pegram, VetCompass PhD candidate at the RVC and lead

"During 20 years as a veterinarian in first opinion practice, I was crying out for good evidence that could help me to provide better care for my patients for common conditions in dogs such as diarrhoea. VetCompass has started to fill these huge information gaps with relevant information based on real-world clinical data. Veterinarians and owners can now feel confident that science is working better for them and their dogs - and that antibiotics are not needed to successfully manage cases of uncomplicated diarrhoea in dogs."

Fergus Allerton, project lead for the PROTECT ME guidelines and co-author of the paper said:

"Rational antimicrobial use is critical to defend ourselves and our pets against the growing threat from antimicrobial resistance. This study provides vital evidence to strengthen recommendations to withhold antibiotics when treating dogs with acute diarrhoea. Knowing that the outcome will be the same without antibiotics should reassure veterinarians to adopt this approach consistently."

Paula Boyden, Veterinary Director at Dogs Trust, said:

"Dogs Trust’s Canine Welfare Grant programme provides funding for research projects with clear pathways to positive welfare outcomes. We are therefore very pleased to have funded the latest study by the Royal Veterinary College which has produced strong evidence for the treatment of canine diarrhoea. Antibiotic resistance has become a major concern in recent years, so having research to show that most cases of diarrhoea can be managed without their use is a significant step forward."


O’NEILL, D. G., JAMES, H., BRODBELT, D. C., CHURCH, D. B. & PEGRAM, C. 2021. Prevalence of commonly diagnosed disorders in UK dogs under primary veterinary care: results and applications. BMC Veterinary Research, 17, 1-14.

The full paper is available from xx am GMT date and can be accessed here:­sone/artic­le’i­d=10.1371/­journal.po­ne.0291057

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