Fecal Water Syndrome in Horses

Researchers determined that fecal water syndrome (FWS) is likely a multifactorial disease, with differences in microbiota noticed between healthy and affected horses.

Normal horse manure (above) comes out in dry-ish balls. Feces of horses with fecal water syndrome (FWS) tend to be normal in consistency, but watery content passes before, during or after defecation. Getty Images

It is somewhat common for equine veterinarians to receive calls from concerned clients that their horse’s manure passes with excess “water.” Feces of horses with fecal water syndrome (FWS) tend to be normal in consistency, but watery content passes before, during or after defecation. Usually there are no signs of intestinal disease, although there is occasional mild discomfort during defecation. If more severe, a horse might experience weight loss, decline in condition and dermatitis along the hind limbs.

A Swiss study attempted to discern if dysbiosis of the intestinal microbiome is a primary contributor to fecal water syndrome [Schoster, A.; Weese, J.S.; Greber, V.; Graubner, C.N. Dysbiosis is not present in horses with fecal water syndrome when compared to controls in spring and autumn. Journal of Veterinary Internal Medicine 2020; DOI:10.1111/jvim.15778].

In a prospective case-control study, the bacterial microbiome of fecal samples from 16 horses with FWS and 15 stable-matched controls were evaluated in spring and autumn of 2016. The duration of FWS lasted more than four months and a horse passed fecal water at least 1 of 2 days over at least a week. Physical exam of the horses was within normal limits. Control horses did not have FWS but were of same age and breed as a case horse. To ensure that husbandry differences would not be an influencing factor in this study, through stabling, control horses had direct contact with a case horse or at least consumed the same water.

Fecal samples were collected over two time points: February-March 2014 and August-September 2014. Half of the horses passed fecal water during winter or spring while 19% passed fecal water throughout the year. The remainder passed fecal water intermittently and in no particular season. 

Gastroscopy and fecal egg counts were performed with no significant difference is gastric ulcer grade or fecal egg counts between affected horses and controls. An ACTH stimulation stress test on salivary cortisol also did not reveal any significant differences.

The results of the study did not identify any significant differences in microbiota composition between horses with FWS and stable-matched controls. 

The authors concluded: “Fecal water syndrome is likely a multifactorial disease. Minor changes in the gut microbiota were present between affected horses and healthy horses, indicating that the microbiota is a potential factor in the development of clinical signs. Additional research is needed to further elucidate the role of the microbiota in FWS and to try and exploit this knowledge for new therapeutic strategies.”

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