Blastocystis isolates from a dog and their owners presenting with chronic diarrhoea. Dogs as reservoirs of Blastocystis: research in Poland and worldwide.

Blastocystis cf. hominis is an unicellular protozoan parasite commonly found in the gastrointestinal tract of humans and animals. Blastocystis is characterized by high morphological and genetic diversity. Studies based on the analysis of Blastocystis spp. small subunit ribosomal RNA genes (SSU rDNA) have identified 26 subtypes (ST) so far, including at least 10 isolated from humans (STs 1-9 and ST12). In 2017, stool samples from a dog and its two owners living in Gdynia, Poland were examined; all three were suffering from chronic diarrhoea. In addition, 30 faecal samples were also examined from 30 dogs kept in one of Warsaw's hotels for animals. Stool specimens were analyzed using anaerobic cultivation at 37°C with a modified Jones' medium and molecular methods (PCR). Phylogenetic analysis using Bayesian inference was performed. Vacuolar forms of Blastocystis were identified in the stool samples of the dog and its owners; Blastocystis were not detected in any sample from the dogs living in the animal hotel. Based on the phylogenetic analysis, the obtained isolates were classified as subtype ST3 (for Owner 1) and subtype ST7 (for Owner 2 and the dog). To the best of our knowledge, the present study is the first to evaluate the presence of Blastocystis in canines in Poland, including domestic dogs.