Probiotics, living microorganisms fed to humans and animals to prevent or treat disease, are an interesting area of ongoing research. I have written about this intervention a number of times (1,2) and it seems a promising area of research, though the current evidence for meaningful beneficial effects is quite limited. There is reasonable evidence for some benefit in treating antibiotic-associated diarrhea or acute diarrhea of unknown cause(3). The evidence is not very good for many other claimed benefits, such as strengthening of immune system function, treatment of kidney disease(4,5), management of feline upper respiratory viral infections(6), and so on. And there are serious problems with irresponsible, excessive hype(7) and poor quality control(8) for probiotics.
Overall, I am cautiously optimistic that we will eventually find legitimate therapeutic uses for some probiotics, though I find the existing evidence unconvincing for most claims currently made about them. A new study looking at the use of Fortiflora, a veterinary probiotic product, for control of diarrhea in shelter animals, does not add much support to the proposed value of this probiotic.
Bybee SN, Scorza AV, Lappin MR. Effect of the Probiotic Enterococcus faecium SF68 on Presence of Diarrhea in Cats and Dogs Housed in an Animal Shelter. J Vet Intern Med. 2011 Jul;25(4):856-60.
Cats in this study were housed for variable periods of time in two rooms, one for previously owned cats and another for feral cats. Canine subjects were also housed in two separate areas. Subjects in both rooms for each species were observed for 4 weeks to establish a baseline incidence of diarrhea in the population. Then subjects in one of the rooms for each species were given Fortiflora daily for 4 weeks while the subjects in the other room were given a placebo. All subjects were taken off the Fortiflora and placebo for one week, and then the treatments were switched, so subjects in the room that had originally received placebo got the Fortiflora and vice versa.
The stool of every animal was scored on a stool consistency chart every day. Abnormal stool samples were evaluated for parasites whenever possible, and an effort was made to evaluate a normal stool from another animal in the same room at the same time to identify what if any role parasites played in the incidence of diarrhea. It is not clear from the paper what if any treatment was given for diarrhea or fecal parasites.
For both dogs and cats, some fecal parasites were detected in some individuals, but the rate of parasitism was no higher in those with diarrhea than in those with normal stools, so the parasites did not seem to influence the incidence of diarrhea significantly in a way that would complicate evaluating the effect of the probiotic. This effect, however, was not especially clear. For the dogs, there was no significant different in the incidence of diarrhea between those getting the Fortiflora and those receiving the placebo regardless of how the data was analyzed. The overall incidence of diarrhea in both groups was lower than expected for reasons that were not identified.
In the cat groups, the overall incidence of diarrhea was no different between the probiotic and placebo groups. However, when the data was broken down to compare the proportion of cats having diarrhea for more than 2 days, this was lower in the probiotic group than in the control group, though the level of significance was not dramatic (P=0.0297 with a cutoff of <0.05).
The authors conclude this finding “suggests the probiotic may have beneficial effects on the gastrointestinal tract.” This is certainly possible, but this particular study provides little support for the idea.