engleski

Prevalence and Molecular Characterization Of Giardia Isolates From Wild Mammals

Wild mammals are commonly infected with Giardia spp., with prevalence rates often over 50%, but there is surprisingly little information on what Giardia species and/or G. duodenalis assemblages they carry. The limited information available indicates that rodents are commonly infected with the non-zoonotic species G. muris and G. microti, whereas other wild animals are infected with both host-adapted (C, D, and E) and zoonotic assemblages (A and B) of G. duodenalis. In this work, faecal samples were collected in Croatia from red deer (Cervus elaphus, n=285), roe deer (Capreolus capreolus, n=14), wild boars (Sus scrofa, n=144), foxes (Vulpes vulpes, n=65), bears (Ursus arctos, n=19), wolves (Canis lupus, n=122), jackals (Canis aureus, n=7), and hares (Lepus europeus, n=73) were examined for the presence of Giardia cysts using microscopy. The prevalence ranged from very low (0% in bears and hares, 1% in deer) to moderate (1.7% in wild boars, 4.5% in foxes, 10% in wolves, 12-5% in jackals) to relatively high (27% in roe deer). DNA was extracted from positive samples and used for PCR experiments. Amplification and sequencing of a fragment of the small subunit ribosomal RNA (ssu-rRNA) gene identified assemblage A in wolves (5 isolates), foxes (1 isolate) and red deer (1 isolate), assemblage C in wolves (2 isolates), a mixed infection with assemblage A and C in a wolf isolate, and assemblage D in red deer (2 isolates) and roe deer (1 isolate). Finally, G. microti was found in a wolf isolate, possibly resulting from the mechanical passage of cyst from an infected prey. This survey, therefore, suggests that the zoonotic risk is mainly linked to the shedding of G. duodenalis assemblage A cyst by carnivores and wild hoofed animals. However, the lack of intra-assemblage sequence variability in the ssu-rRNA gene limits the possibility to evaluate the actual zoonotic potential of G. duodenalis cysts typed as assemblage A. For this purpose, a comparative analysis of subtypes defined by sequencing more variable genes (such as the triose phosphate isomerase) is required. This work is in progress in our laboratory, and the data generated so far indicated the presence of subtype AI in isolates from a wolf and a red deer, and subtype AIII in a wild boar isolate. As these subtypes are rarely found (AI) or absent (AIII) in G. duodenalis isolates from humans, the role of wild mammals in the transmission of giardiasis to humans appears to be minimal.

Giardia; wildlife; multilocus genotyping; prevalence; zoonotic

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