Association between Giardia infection and pruritic skin disease in dogs
Recent reports in the human and veterinary literature have suggested that 'Giardia' infection may be linked to the development of pruritus and other allergic clinical signs. In order to determine if there is an association between infection with 'Giardia' and pruritus, three fecal samples were collected over seven days from 71 pruritic dogs and 101 clinically normal dogs from southern Ontario during the period March 2002 to March 2003. Each fecal sample was evaluated for 'Giardia' cysts using a zinc-sulfate concentration technique, and a random sample from each animal was evaluated for the presence of 'Giardia'-specific antigen using an enzyme-linked immunosorbent assay (ELISA). A positive result on either test was considered evidence of 'Giardia' infection. The prevalence of 'Giardia' in clinically normal dogs was 9.9%, but 0% for dogs with pruritic skin disease (P = 0.006). The results of this study suggest a negative association between 'Giardia' infection and pruritic skin disease. It should be noted that cephalexin use may be an explanatory variable for our observations since all cephalexin use was in the pruritic group. Feces from clinically normal and pruritic dogs were also examined for other intestinal parasites. The following parasites, with their respective prevalence, were identified in the fecal samples from the 172 dogs: ' Isospora' spp. (11.6%), 'Toxocara canis' (4.1%), ' Trichuris vulpis' (2.9%), 'Ancylostoma caninum' (2.3%), ' Sarcocystis' spp. (1.2%), 'Alaria' spp. (0.6%), ' Strongyloides stercoralis' (0.6%), 'Toxascaris leonina' (0.6%) and 'Uncinaria stenocephala' (0.6%). The prevalence of most parasites was similar for mixed-breed dogs and purebred dogs, except for 'Isospora' spp., which showed a higher prevalence in mixed-breed dogs (P = 0.067). Clinically normal dogs showed a wider range of parasite species (P = 0.066) compared to dogs presented to referral dermatology services.