Frequency of intestinal parasites in pet dogs from an urban area (Greater Oporto, northern Portugal).

The present study was conducted to evaluate the prevalence of gastrointestinal parasites in dogs with no clinical signs (n=175; group H) and in dogs with gastrointestinal disease (n=193; group D) that were admitted to a veterinary hospital. In group H, the overall prevalence of intestinal parasites (i.e. the presence of at least one species) was 20.6%. Cystoisospora canis was the most prevalent protozoon (8.0%) followed by Giardia spp. (7.4%); Toxocara canis (5.1%) was the most frequent helminth, followed by Trichuris vulpis (1.1%) and Toxascaris leonina (0.6%). Among group H, age ≤ 6 months was found to be a risk factor for infection with C. canis and with at least one agent (odds ratio [OR]=3.4). In group D parasites were found in 33.7% of the dogs, with Giardia spp. (15.5%) being the most prevalent species, followed by C. canis (13.5%), T. canis (7.8%), T. vulpis (2.6%) and T. leonina (0.5%). In group D dogs, age ≤ 6 months was a risk factor for infection with Giardia spp. (OR=3.2), with C. canis (OR=32.7) and with at least one agent (OR=7.2). This study reveals a remarkable number of dogs infected but with no clinical signs.