Trend analysis of Trichinella in a red fox population from a low endemic area using a validated artificial digestion and sequential sieving technique

Abstract

Freezing of fox carcasses to minimize professional hazard of infection with Echinococcus multilocularis is recommended in endemic areas, but this could influence the detection of Trichinella larvae in the same host species. A method based on artificial digestion of frozen fox muscle, combined with larva isolation by a sequential sieving method (SSM), was validated using naturally infected foxes from Latvia. The validated SSM was used to detect dead Trichinella muscle larvae (ML) in frozen muscle samples of 369 red foxes from the Netherlands, of which one fox was positive (0.067 larvae per gram). This result was compared with historical Trichinella findings in Dutch red foxes. Molecular analysis using 5S PCR showed that both T. britovi and T. nativa were present in the Latvian foxes, without mixed infections. Of 96 non-frozen T. britovi ML, 94% was successfully sequenced, whereas this was the case for only 8.3% of 72 frozen T. britovi ML. The single Trichinella sp. larva that was recovered from the positive Dutch fox did not yield PCR product, probably due to severe freeze-damage. In conclusion, the SSM presented in this study is a fast and effective method to detect dead Trichinella larvae in frozen meat. We showed that the Trichinella prevalence in Dutch red fox was 0.27% (95% CI 0.065-1.5%), in contrast to 3.9% in the same study area fifteen years ago. Moreover, this study demonstrated that the efficacy of 5S PCR for identification of Trichinella britovi single larvae from frozen meat is not more than 8.3%.

The red fox ( Vulpes vulpes ) plays a minor role in the epidemiology of the domestic cycle of Trichinella in Romania

“…Because the majority of the tested muscles had previously been frozen, we cannot exclude the possibility that some larvae were lost in the sedimentation step, particularly in the minimally infected muscles, because such losses have been previously shown by other authors (Mayer-Scholl et al, 2013;Franssen et al, 2014). It follows that the true prevalence of Trichinella spp.…”

Trichinella spp. biomass has increased in raccoon dogs (Nyctereutes procyonoides) and red foxes (Vulpes vulpes) in Estonia

“…In experimentally infected raccoon dogs, the T. nativa larval density in masseter muscle was about half of that in foreleg muscles [ 58 ]. The storage conditions and transport time could also affect the results [ 29 , 40 , 60 ].…”

Helminth parasites in black rats (Rattus rattus) and brown rats (Rattus norvegicus) from different environments in the Netherlands

“…After two successive sedimentation steps, the resulting suspension was transferred to petri dishes and examined microscopically for isolated larvae. Muscle samples of 20 animals that had been frozen before were analysed using a validated sequential sieving method to detect Trichinella larvae ( 10 ).…”