A timely and prompt diagnosis in horses of a Clostridioides difficile infection leading to treatment with the antibiotic metronidazole improves outcomes, researchers report.
The spore-forming bacterium is one of the causes of colitis (colon inflammation) in humans, especially during antimicrobial treatment and hospitalisation.
C. difficile has also been isolated from animals, which are often symptom-free. However, the bacterium is known to cause disease in certain animals, including horses and pigs.
In horses, it is one of the most important causes of colitis. Cases in horses have been reported worldwide, Eri Uchida-Fujii, Hidekazu Niwa and their fellow researchers noted in the journal Scientific Reports.
Disease in horses ranges from mild to severe, and can be fatal. Around 6 to 8% of healthy horses are also thought to harbour C. difficile.
Researchers set out to perform a molecular study of C. difficile samples taken from C. difficile cases among Japanese Thoroughbreds. They also sought to evaluate the disease-causing ability of each genotype by linking their genetic analysis to case outcomes.
Their work centered on 34 cases from 2010 to 2021, from which 38 C. difficile strains were isolated. All of the horses developed severe colitis. Twenty-two of the horses (64.7%) were hospitalised at the onset of colitis. Outcomes were balanced for hospitalisation rates at the onset of colitis.
The study team found that the death rates of cases treated with metronidazole (65.0%) were significantly lower than untreated cases, in which all died.
Overall, nearly 80% of the horses died or were euthanised.
The study team noted that in 2013 veterinarians started to use metronidazole for C. difficile cases at the two equine hospitals at the center of the study.
An earlier study that reviewed the same cases suggested that metronidazole treatment reduced the mortality rate, even though the number of cases was too low to obtain adequate statistical power. The effect of metronidazole treatment was clearly significant, they said.
Treatment with metronidazole would be a major factor for recovery from C. difficile in these cases, the study team said, even though the accumulation of experience by the veterinarians, early diagnosis, and improvements in supportive care might also have contributed to better outcomes.
“Our study suggests that metronidazole treatment is needed for horses with adequately diagnosed C. difficile infections,” they concluded.
In addition, monitoring the number of cases and their prognosis in horses should be continued to establish better approaches for the treatment and prevention of such infections.
Finally, to understand the transmission route of C. difficile and to prevent healthcare-associated infections in horses, strain-based surveillance of the bacterium should be continued, they said.
Genotyping for C. difficile of animal origin is important for understanding the presence and transmission of the pathogen among humans, animals, and the environment.
“Further investigations of C. difficile infections in horses might contribute to understanding its potential role as a zoonotic pathogen in terms of One Health.”
The study team comprised Uchida-Fujii, Niwa, Yuta Kinoshita and Takanori Ueno, all with the Microbiology Division, part of the Equine Research Institute of the Japan Racing Association; Mitsutoshi Senoh and Haru Kato, with Japan’s National Institute of Infectious Diseases; and Hiroshi Mita, with the Clinical Veterinary Medicine Division, part of the Equine Research Institute at the Japan Racing Association.
Uchida-Fujii, E., Niwa, H., Senoh, M. et al. Clostridioides difficile infection in thoroughbred horses in Japan from 2010 to 2021. Sci Rep 13, 13099 (2023). https://doi.org/10.1038/s41598-023-40157-x
The study, published under a Creative Commons License, can be read here.
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