Are fecal transplants the way forward for horses with diarrhea?

Veterinarians Caroline McKinney, left, and Daniela Bedenice are part of a team investigating the effects of fecal transplant on the gut of horses being treated for diarrhea. Photo: Alonso Nichols

Fecal transplants may represent a cost-effective way to restore gut function in horses with serious diarrhea, researchers have concluded.

Fecal microbial transplantation (FMT), as it is known, is used to treat some people whose gastrointestinal problems are related to imbalances in the make-up of their gut microbes.

With the reported success in humans, it has also been used in some horses with similar issues, given that diarrhea can pose a serious health risk to horses.

It can easily turn deadly in horses, killing some 25 to 30 percent of affected animals.

Researchers from Tufts University in Massachusetts set out to learn more about fecal microbial transplants in horses. Indeed, researchers at the university’s Cummings School of Veterinary Medicine are considered pioneers in the field.

Caroline McKinney and her colleagues used molecular-based testing to compare the fecal microbial profile of healthy horses to that of elderly horses with diarrhea who received fecal transplants.

They wanted to know whether the transplants restored microbial diversity, and whether it brought about any improvement.

First, fecal samples were collected from the rectum of 15 healthy young-adult horses, aged 2 to 12 years for analysis, as were samples from 15 healthy horses aged 20 or more. The horses were housed at five facilities across Massachusetts.

The study team, writing in the open-access journal PLOS ONE,  found that age did not significantly affect the healthy equine fecal microbiota, indicating that both healthy geriatric and young-adult horses may serve as fecal donors for transplants. In contrast, diet and farm location did affect the microbial make-up.

The five older horses selected to receive fecal transplants were hospitalized at Tufts Cummings School of Veterinary Medicine with diarrhea.

Fecal microbial transplants were performed for three consecutive days in the five using feces from the same healthy donor.

Veterinarian Caroline McKinney, left, works with molecular biologist Giovanni Widmer, whose lab is conducting genetic analyses to see how fecal transplants affect sick horses’ gastrointestinal microbiome. Photo: Alonso Nichols

Fecal samples were collected for analysis from both the donor and recipients before each transplant, and 24 hours after.

The horses stayed in the hospital for between 5 to 8 days, with 3 of the 5 surviving to discharge.

The research team found that the fecal microbiota of horses with diarrhea was significantly more variable in terms of β-diversity than that of healthy horses.

At study completion, the fecal microbiota of horses that responded to the fecal transplant had a higher α-diversity (higher species richness) than before treatment, and a greater abundance of Verrucomicrobia. Their microbial make-up was found to have become more similar to that of the donor.

The fecal transplants brought about an improvement in the surviving horses, all of whom had been suffering from acute or progressive diarrhea.

The researchers say that re-establishing a healthy gut microbiome in horses with gut inflammation is considered essential to digestion. It is expected to act as a bulwark against harmful bacteria and may help the development of a robust and effective immune system to counteract infection.

“Additionally, normal microbial inhabitants of the gut are thought to help maintain a balance between inflammatory and anti-inflammatory mediators in the intestinal tract, and may stimulate mucus production that prevents the attachment of pathogenic bacteria.”

The observed increase in the relative abundance of mucus-dwelling Verrucomicrobia is consistent with increased mucus production, which serves as a barrier to pathogens.

“As such, fecal microbial transplantation could aid in the restoration of gut function in horses with colitis and resolution of diarrhea.”

They continued: “Bacterial species richness and diversity are important elements of a healthy intestinal microbiome.

“It has been well established in horses that systemic antimicrobials lead to changes in the intestinal microbiota, with different and specific responses to different antimicrobials.

“Whether fecal microbial transplantation can mitigate or reverse intestinal dysbiosis (microbial imbalance) in the face of concurrent antimicrobial administration has not been established to date.

“Overall,” they wrote, “this preliminary work supports fecal microbial transplantation as a mechanism for establishing a more diverse microbiome in horses with colitis and may thus represent a cost-effective therapy to facilitate restoration of gut function in horses with dysbiosis or colitis.”

The researchers say larger case-controlled studies are needed to ensure the reliability of their results.

They noted that while the fecal microbiome assessment of both healthy geriatric and young-adult horses suggests that age-matching between donors and recipients is not necessary to optimize microbial transplantation, diet-matching may be prudent.

The study team comprised McKinney, Bruno Oliveira, Daniela Bedenice, Mary-Rose Paradis, Melissa Mazan, Sophie Sage, Alfredo Sanchez and Giovanni Widmer.

McKinney CA, Oliveira BCM, Bedenice D, Paradis M-R, Mazan M, Sage S, et al. (2020) The fecal microbiota of healthy donor horses and geriatric recipients undergoing fecal microbial transplantation for the treatment of diarrhea. PLoS ONE 15(3): e0230148.

The study, published under a Creative Commons License, can be read here

Earlier related report 

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