I’ve written before on the subject of probiotics, bacteria or yeast fed to people or animals with the intent of affecting health in some way. I consider them to be in a bit of a gray zone between mainstream medicine and CAM. There is some plausibility to the underlying idea, and there is some clinical evidence that probiotics can be helpful for GI problems such as antibiotic-associated diarrhea and community acquired diarrhea. However, the wild claims that are sometimes made about probiotics of “boosting the immune system” and treating virtually any disease whether related to the GI tract or not fall into the realm of CAM.
A colleague recently went to a continuing education conference and reported that one of the speakers suggested a particular probiotic product, Fortiflora, can help with symptoms of Herpesvirus rhinitis. Feline herpesvirus 1 (FHV-1) is a ubiquitous viral infection that in some cats can cause chronic, recurrent rhinitis, with sneezing, nasal discharge, and often concommitant conjunctivitis (red, watery eyes). These symptoms come and go, especially with various kinds of stress, and there is no cure and limited benefit from vaccination and oral medications.
I was curious about the evidence for the claim that Fortiflora might help cats with herpesvirus rhinitis since the disease is a common and frustrating one and since the idea that bacteria (specifically Enterococcus faecium) fed to an animal to affect the makeup of the normal GI microflora should help nasal and eye symptoms doesn’t seem to make sense at first glance. My colleague was kind enough to ask the speaker at the conference to send the research paper he had written on the topic, which I reviewed(Lappin MR, Veir, JK, Satyaraj E, Czarnecki-Maulden G. Pilot study to evaluate the effect of oral supplementation of Enterococcus faecium SF68 on cats with latent feline herpesvirus 1. Journal of Feline Medicine and Surgery 2009;11(8):650-4). The experiment was only a small pilot study, and more research on the subject may be warranted, however the existing data do not provide much support for the notion that this product has a role in the treatment of herpesevirus rhinitis.
The study involved 12 cats which had previously been documented to have FHV-1 infection and symptoms of conjunctivitis. The subjects were randomly allocated to a group supplemented with Fortiflora and a control group given an appropriate placebo. They were subjected to stresses such as housing changes and spaying or neutering, and the frequency of clinical symptoms was monitored, as well as measures of GI microflora diversity and PCR to look for shedding of active FHV-1.
Prior to the onset of the study, the cats in the treatment group had a lower rate of conjunctivitis than the control group (13% vs 21%), though this was not statistically significant and might have been due to random chance. There was no significant change in conjunctivitis symptoms for the treatment group during the study (up to 16%), but the placebo group appeared to worsen (up to 29%) which created a significant difference between the groups in symptoms during the treatment period. Of the 6 cats in the supplementation group, conjunctivitis got significantly better in one and significantly worse in another during the treatment period. Of the control cats, one’s symptoms got significantly worse. There was not significant change in symptoms for the remaining 9 of the cats. Respiratory signs were rare in both groups and no differences were measured. With such a small number of cats in the study, it is difficult to view such mixed results as definitively showing or disproving an effect of the treatment on symptoms.
Microbial diversity in the feces (based on PCR) decreased significantly in the placebo group, though there were no significant differences between the level of diversity when the placebo and control groups were compared at any point. Despite some claims of relevance for overall immune function, there is no sound evidence that such measures of diversity represent clinically significant effects on susceptibility to disease. This is typical of studies of probiotics which tend to show that their use does something but which doesn’t tell us what if any real-world significance these effects might have.
Some intermittent shedding of active FHV-1 virus was detected in some cats, but there were no differences between individuals or groups in this measure. There were also no detectable differences in FHV-1 antibody levels or other measures of immune function between groups.
So overall, the study provides little support for the thesis that Fortiflora boosts general immune function in a way that would be clinically useful for cats with FHV-1 rhinitis. Certainly, the additional research the authors suggest is needed may provide greater evidence for this hypothesis, or it may show no meaningful effect. The authors are clearly good scientists, and they are careful in their paper not to make dramatic claims not supported by the data. They tend, as we all do, to interpret the results of their efforts in the most positive light, which is why independent replication of new findings is so important in science. However, the problem with traditional “opinion-based medicine” is to that the theories and opinions of smart and experienced scientists such as these authors are given great weight by those of us in general practice, and there is a tendency to make changes in clinical practices not justified by the quality of the data. This paper is interesting, and the line of inquiry may lead somewhere eventually, but it does not justify the widespread use of Fortiflora for FHV-1 rhintis.
The argument that probiotics “boost the immune system” in general is not a very convincing one, as illustrated in a critique of the concept by Dr.Mark Crislip at Science-Based Medicine. There is no clinical trial evidence that shows resistance to infectious disease can be enhanced in a healthy, normal person. Certainly, white blood cells and inflammatory mediators can react in a variety of ways to all kinds of stimuli, in test tubes and in living organisms. But the connection between these reactions and a meaningful improvement in resistance to disease has yet to be made. Probiotics undoubtedly have some benefits, however the GI microflora and its role in immune function is a dazzlingly complex subject which science is only beginning to understand. Most of the normal organisms present in healthy people and animals have not been identified, and the ecological niche or function of these organisms isn’t known. The effect of tinkering with this complex system without understanding it is ultimately unpredictable, and the assumption that such tinkering must be beneficial is unwarranted. As our basic understanding of the topic improves, I hope targeted probiotic therapies for specific problems will continue to emerge. But at this point, there is little scientific justification for the widespread use of such products for nearly any condition with the assumption of safety and efficacy.