Giardiasis and diarrhea in dogs: do the microbiome matter?

Abstract

Abstract Background Giardia duodenalis (Gd) causes intestinal parasitosis; nevertheless, the intestinal microbiome involvement in determining the clinical phenotype of infection is unknown. This cross-sectional study aimed to investigate fecal microbiome features in dogs with giardiasis and included fecal samples of kenneled dogs diagnosed with Gd by fecal Giardia antigen dot ELISA. The fecal microbial compositional characteristics and the dysbiosis index (DI) were compared between diarrheic and non-diarrheic dogs. Results The study included 38 fecal samples of Gd-infected dogs (diarrheic, 21; non-diarrheic, 17). There were no group differences in Faith's phylogenic diversity and beta diversity (weighted UniFrac distances) and in specific taxa abundances at the phylum, genus, and species levels, as well as in alpha and beta diversities between diarrheic and non-diarrheic dogs divided by sex or age. In diarrheic dogs, alpha diversity was higher in males than in females (pairwise Kruskal-Wallis: q = 0.01). Among males, fecal abundances of the genus Clostridium (W = 19) and Clostridium spiroforme species (W = 33) were higher in diarrheic compared to non-diarrheic dogs. In diarrheic dog fecal samples, Proteobacteria were more prevalent (W = 1), while Verrucomicrobia were less prevalent, in dogs aged < 1 year than in older dogs. Fecal samples of 19 diarrheic, and 19 non-diarrheic dogs showed similar DI (median, -0.2; range, -4.3-4.5; and median, -1.0; range, -4.3-5.8, respectively). Conclusions The fecal microbial composition of symptomatic and asymptomatic dogs with giardiasis is similar. Based on the DI, giardiasis is not characterized by prominent dysbiosis. Other host and parasite characteristics may play important roles in determining the severity of giardiasis in dogs.