The clinical significance of Cyniclomyces guttulatus in dogs with chronic diarrhoea, a survey and a prospective treatment study.

This study surveyed the prevalence of massive numbers of Cyniclomyces guttulatus in faecal samples from healthy dogs (18%) and dogs with chronic diarrhoea (14%) suggesting that this yeast has no clinical significance. Subsequently, a total of 57 referred dogs with chronic diarrhoea were selected because they excreted massive numbers of C. guttulatus and their initial diagnostic work-up yielded no other direct clues explaining their diarrhoea. Treatment with nystatin did not result in any clinical response in 36 out of these 57 dogs (63%), although they no longer shed the yeast. However, a response was noted in the remaining 21 (37%) dogs: 13 were 'responders', in that their diarrhoea subsided for more than two weeks and the faeces were cleared of the yeast. However, three of these dogs relapsed repeatedly, with signs of diarrhoea and massive shedding of the yeast. The other eight dogs were 'incomplete responders', whereby faecal quality initially normalised, but diarrhoea relapsed within two weeks, whilst still not shedding the yeast. In these cases, further diagnostic work up revealed other co-causes of diarrhoea. It was concluded that there was no direct evidence that C. guttulatus is a primary pathogen. However, the results of the prospective treatment study suggest that a possible role in a minority of cases, perhaps as an opportunist, cannot be ruled out.