Trichinella spp. in wild boar (Sus scrofa) populations in Croatia during an eight-year study (2010-2017)

Wild animals represent a constant source of Trichinella spp. infections for domestic animals and humans. To date, four species of Trichinella have been isolated in wild boar populations in Europe: T. pseudospiralis, T. spiralis, T. britovi and T. nativa, in addition to several mixed infection types and one hybrid formation between T. britovi and T. spiralis. Meanwhile, insufficiently thermally processed wild boar meat has been reported to be a source of trichinellosis in humans in several European countries. In Croatia, there have been no reported or proven cases of trichinellosis caused by wild boar meat consumption. The aim of this study was to obtain data on the prevalence of Trichinella species present in Croatia and to anticipated the potential risk of infection for humans in specific Croatian regions based on information obtained over an eight-year surveillance period. A veterinary inspection of wild boar carcasses for Trichinella larvae in Croatia has been mandatory since 1989, and the artificial digestion method was introduced as a compulsory test for wild boar samples in 2008. Based on the official data submitted to the Ministry of Agriculture, Directorate of Veterinary Services, in the period 2010-2017, 303 of 183,184 (0.17%) wild boar meat samples tested positive for Trichinella spp. Infected wild boar were found in 18 of 21 counties. Of these positive samples, 85 were submitted by the authorised veterinary inspectors to the National Reference Laboratory for further examination. The intensity of infection in muscle samples was 0.04-152.66 (mean: 23,37) larvae per gram, and Trichinella species were identified as T. spiralis, T. britovi, T. pseudospiralis and T. spiralis + T. britovi. Genetic analysis of T. pseudospiralis isolates demonstrated their belonging to the Palaearctic population.