Genetic identification of Giardia isolates from symptomatic and asymptomatic shelter dogs

Giardia cysts were obtained from a cohort of 20 infected shelter dogs with diarrhoea (n = 10) or asymptomatic (n = 10), and were examined by molecular methods that included DNA extraction, triosephosphate isomerase gene amplification, and DNA sequence analysis. Results showed the presence of Assemblages A and C. Three samples belonged to Assemblage A (subgenotype A1) but the majority (17) to Assemblage C. A degree of genetic polymorphism was evident within Assemblage C with 2 subgenotypes identified (C1 and C2). This suggests that infection of humans by zoonotic Assemblage A from shelter dogs is of limited epidemiological significance, though possible. The relation between presence or absence of diarrhoea and Giardia Assemblages or subgenotypes was also investigated by Fisher's Exact Test. No statistical relation was detected. Therefore, it is concluded that host factors probably play a major role in the clinical manifestation of Giardia infections in dogs