engleski

Unique Dicrocoelium dendriticum genotypes from Croatian brown bears

The lancet liver fluke Dicrocoelium dendriticum occurs in various domestic (sheep, goats, cattle, horses, rabbits, dogs) and wild (deer, wild boar, buffalo, camels) mammals and humans around the globe. Since reports of D. dendriticum in large carnivores are limited, like in the brown bear (Ursus arctos), we performed the study to investigate the presence and the prevalence of D. dendriticum in free ranging brown bears from different Croatian regions. Data on age, gender, location at the time of death, season, intensity of infection and pathohistological changes have been collected from infested animals. Parasites from bears, goat and sheep were further genotyped to investigate possible genetic difference among D. dendriticum isolates. Between February 2014 and December 2016, we sampled the complete gall bladders and liver samples of 136, hunted and dead due to other causes, brown bears across the bear range in Croatia. Each gallbladder and content was washed through the sieve to detect and count each parasite. We found that 60% of the examined brown bears were infected, ranging from 1- 103 parasites (mean=16.31, median=1) without differences in prevalence related to location, gender or age class. Seasonal distribution of Dicrocoelium infestation indicated a significantly higher percentage of infestation in autumn (mid August-December, 72%) compared to spring (February-May, 45% ; p=0.00192). Sequencing of ITS-1 of individual D. dendriticum from 16 bears, 5 sheep and one goat didn’t show any heterogeneity. COX1 sequences were identical from all bears from various regions showing differences in 7 nucleotide position with similarity of 98% with small ruminant isolates. To evaluate possible genetic variability of D. dendriticum within single bear COX1 was sequenced from 3-5 adult flukes from 10 bears without any SNP. Histopathology showed granulation of the surface of the liver and hepatomegaly in infested individuals, as well as enlarged gall bladders with firmer consistency of bile ducts surrounding the parenchyma. In the current survey we have presented evidence that bears could serve as final host of potential new “bear” genotype of D. dendriticum. This finding also suggests possible adaptation of D. dendriticum and unique life cycle of “bear” isolate.

lancet liver fluke, Dicrocoelium dendriticum, brown bear, Ursus arctos, Croatia, genotype

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