Epidemiology and genetic diversity of Blastocystis sp. in dogs housed in sanitary and rescue shelters

INTRODUCTION. Blastocystis is an intestinal protist associated with gastrointestinal disorders and affecting worldwide both humans and a wide range of animals. Up-to-now, 17 Blastocystis subtypes (STs) have been recognized on the basis of subunit ribosomal RNA gene (SSU-rDNA) analysis, being ST1-ST4 the most commonly found in humans. Among domestic animals, dogs seem to be involved in the spread and maintenance of the infection, naturally harboring STs in common with humans. With the aim of investigate on dogs as a potential source of Blastocystis infection to humans, an epidemiological survey on kennels’ dogs in Lombardy was planned, to evaluate the prevalence of Blastocystis infection and the STs involved. MATERIALS AND METHODS. Ninety-nine individual fecal samples were collected in six kennels, with an average of 19 animals per surveyed kennel. Samples included eight pure breeds and cross-breeds, and animals of varying age from three months to 14 years. Genomic DNA was extracted from each sample using a commercial kit; the DNA samples were subjected to PCRs in order to amplify a fragment of about 600 base pair within the 1800 bp SSU-rDNA of Blastocystis (Scicluna et al., 2006. Protist. 157: 77–85) and the fragments obtained purified for sequencing. STs were identified aligning obtained sequences with available published ST1-ST10 sequences. To infer the phylogenetic relationships among the sequences, a phylogenetic tree was constructed by using the neighbor-joining (NJ) method in MEGA v.6.0.6 software. RESULTS AND CONCLUSIONS. Twenty-one fecal samples proved to be positive by PCR (21.2%), with prevalence values ranging from 18.2% to 37.5% according to the kennels; all dogs from one kennel scored negative for Blastocystis. Sequences obtained showed a high identity (98–100%) to homologous sequences of Blastocystis isolates previously reported in GenBank. The phylogenetic analysis showed that all sequences clustered with ST3 in a monophyletic group with a high bootstrap value (>95), being the first report in Italy of this ST in dogs. Previous surveys carried out in Italy showed the occurrence of ST3 as the most prevalent in human fecal samples (Mattiucci et al., 2016, Epidemiol Infect. 144:635-646. Meloni et al., 2011. Parasitol Res. 109:613-619); the results obtained in the present survey suggest dogs as possible zoonotic reservoirs for the parasite.