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

Abstract

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.

Trichinella britovi in wild boar meat from Italy, 2015–2021: A citizen science approach to surveillance

“…However, the finding of T. britovi as the only Trichinella spp. in wild boars of the study area corroborates this species as the main circulating in the Mediterranean basin [ 25 ], unlike the central European countries where T. spiralis is notoriously widespread [ 9 ]. In fact, although T. spiralis and T. britovi occasionally occur in sympatry, their territorial separation could be due to the biological ability of the first species to inhibit infections in the host by the second one [ 9 ].…”

“…The low overall prevalence (i.e., 0.01%) of T. britovi in wild boar populations of Italy is consistent with that of Hungary (0.01%) [ 21 ] and Croatia (0.07%) [ 9 ], although higher rates of infection are reported in these ungulates from Estonia (0.7%) [ 22 ] and Latvia (2.2%) [ 23 ]. Indeed, this significant difference of infection prevalence in different countries would confirm the greater occurrence of T. britovi in the north than in the south of Europe, due to a plethora of environmental conditions which favour the survival of larvae in decaying muscles of animal carcasses [ 24 ].…”

“…Despite this, in European countries few large-scale studies are available on the occurrence of Trichinella spp. in wild boars, even if their meat products are commonly present in local markets and traditional festivals [ 8 ], being considered as a delicacy and touristic attractiveness due to the nutritional and culinary properties [ 9 ]. According to the European legislation on specific rules for official controls of Trichinella in meat (i.e., the Commission Implementing Regulation EU 2015/1375 and 2019/627) [ 10 , 11 ], all quarry susceptible to this parasite should be screened for presence of larvae (L 1 ) in the muscles before being placed on the market for human consumption.…”

The International Trichinella Reference Centre database. Report on thirty-three years of activity and future perspectives

“…Indeed, while the predominant association of T. spiralis with wild boars and domestic pigs (89.4%) agrees with literature ( EFS Agency, 2021 ; Pozio, 2021 ), the large number of T. britov i isolates associated with wild boars (41%), rather than with red foxes (26.3%), does not reflect the real epidemiological situation in which the red fox is the main natural host of this species ( Bilska-Zając et al, 2020 ; Deksne et al, 2016 ; Kärssin et al, 2017 ). This is due to the fact that the T. britovi isolates recorded in the DB mainly originated from surveillance studies with a specific focus on wild boar ( Bilska-Zając et al, 2013 ; Kirjušina et al, 2015 ; Balić et al, 2020 ; Vieira-Pinto et al, 2021 ). Likewise, the high association of T. pseudospiralis with the Florida panther and that of T6 with the wolverine in isolates collected from North America ( Reichard et al, 2008 ; Reichard et al, 2015 ), reflects data derived from surveillance studies focused on specific host species because of their interest as possible Trichinella indicators in a specific geographical region.…”

Investigation of the Food-Transmitted Parasites Trichinella spp. and Alaria spp. in Wild Boars in Greece by Classical and Molecular Methods and Development of a Novel Real-Time PCR for Alaria spp. Detection

“…Nevertheless, the prevalence found in wild boars in Europe may be characterized as low, as it has been found less than 1% in all cases. In some of the most recent, wide-range epizootiological surveys in Europe where AD methods were implemented, hundreds or thousands of wild boars were examined (in most cases these surveys were analysis of national authorities' records); the prevalence of infection was 0.1% in Portugal [48], 0.17% in Croatia [49], 0.04% in Slovakia [50], 0% in Denmark [51], and 0.51% in Poland [52]. In a survey similar to the present study, conducted in Italy, diaphragm muscle samples of 100 wild boars hunted in two hunting seasons were examined, and none (0%) was found positive to Trichinella larvae [53].…”