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The use of serological tests to detect Trichinella infection in domestic and wild animals and in humans has not been standardised yet. This review provides an uniform set of recommendations for the development and use of serological tests to detect circulating antibodies in serum samples. The recommendations are based on the best scientific published information and on the unpublished data from laboratories with a great expertise in this field and represent the official position of the International Commission on Trichinellosis regarding acceptable methods and the evaluation of the sensitivity and specificity. These recommendations are subject to change as new scientific information becomes available.

The tolerance to degradation processes in meat of nine Trichinella genotypes was studied in mouse and fox tissue, respectively. Minced muscle tissue with Trichinella larvae of different age was stored at room temperature at 100 % relative humidity. During storage weekly sub samples of the minced meat were digested and released larvae were inoculated in mice to evaluate the Reproductive Capacity Index (RCI). The RCI decreased with the length of storage, but the larvae from older infections appeared better adapted to tolerate the degradation processes. The African species T. nelsoni had a relative higher tolerance to elevated temperature during storage and the unencysted species T. pseudospiralis was the most vulnerable genotype.

Isoenzyme-based approach was applied to compare Trichinella spiralis, T. britovi and T. pseudospiralis species. Among 13 enzyme systems examined, esterase (EST), malic enzyme (ME) and phosphoglucomutase (PGM) have been found as fully diagnostic, with no common allele in species studied. Adenosine deaminase (ADA), adenylate kinase (AK), hexokinase (HK), peptidase leucyl-alanine (PEP-C) and fructose-bis-phosphatase (FBP) have been capable of distinguishing the two species from resulting profiles. In addition, ADA, AK and PGM displayed the enzyme expression in the lowest amounts of muscle larvae in systems tested ( 100 larvae/100 μl of extracts). Based on allozyme data, T. pseudospiralis has been found as the most distinct species within the group of taxa. Only a subtle genetic variability was recorded for T. pseudospiralisin which solely phosphoglucomutase exhibited variant patterns. In addition to the study of reference isolates, T. spiralis from lowland fox in Eastern Slovakia has been evidenced by use of genetic markers. This finding has proved that T. britovi is not the exclusive species parasitizing in the sylvatic ecosystem of the Slovak region.

Abstract: Only a few studies have compared the muscle distribution of the different Trichinella genotypes. In this study, data were obtained from a series of experimental infections in pigs, wild boars, foxes and horses, with the aim of evaluating the predilection sites of nine well-defined genotypes of Trichinella. Necropsy was performed at 5, 10, 20 and 40 weeks post inoculation. From all host species, corresponding muscles/muscle groups were examined by artificial digestion. In foxes where all Trichinella species established in high numbers, the encapsulating species were found primarily in the tongue, extremities and diaphragm, whereas the non-encapsulating species were found primarily in the diaphragm. In pigs and wild boars, only Trichinella spiralis, Trichinella pseudospiralis and Trichinella nelsoni showed extended persistency of muscle larvae (ML), but for all genotypes the tongue and the diaphragm were found to be predilection sites. This tendency was most obvious in light infections. In the horses, T. spiralis, Trichinella britovi, and T. pseudospiralis all established at high levels with predilection sites in the tongue, the masseter and the diaphragm. For all host species, high ML burdens appeared to be more evenly distributed with less obvious predilection than in light infections; predilection site muscles harbored a relatively higher percent of the larval burden in light infections than in heavy infections. This probably reflects increasing occupation of available muscle fibers as larger numbers of worms accumulate. Predilection sites appear to be influenced primarily by host species and secondarily by the age and level of infection. [Copyright &y& Elsevier]

Abstract: Vertical transmission of Trichinella spiralis was evaluated in ferrets (n =21), foxes (n =11), pigs (n =12), guinea pigs (n =16), and mice (n =41). The placental barrier to be crossed by migratory Trichinella larvae varies structurally in different animal species. Ferrets and foxes have an endotheliochorial placenta structure, guinea pigs and mice a haemochorial, and pigs an epitheliochorial placenta. The non-encapsulating Trichinella pseudospiralis larvae have an extended muscle migration prior to entering a muscle cell. To evaluate if T. pseudospiralis was more likely to be transmitted to offspring, an additional group of foxes (n =11) infected with T. pseudospiralis was included. Two different dose levels were used for ferrets, pigs, guinea pigs, and mice. In pigs and guinea pigs, infection was given at different times of the gestation period. Vertical transmission, measured as recovery of muscle larvae in the offspring, was demonstrated in both ferrets groups, in all four guinea pig groups, and in the high dose mouse group, but not in any fox or pig groups. [Copyright &y& Elsevier]

The susceptibility of seals to infection with Trichinella nativa and the cold tolerant characteristics of muscle larvae in seal meat were evaluated. Two grey seals, Halichoerus grypus, were inoculated with 5,000 (100 larvae/kg) T. nativa larvae and two grey seals with 50,000 (1,000 larvae/kg). One seal from each dose group and two control seals were killed at 5 and 10 weeks post-inoculation (p.i.). At 5 weeks p.i., infection was established in both low and high dose seals with mean larval densities of 68 and 472 larvae per gram (lpg), respectively, using eight different muscles for analyses. At 10 weeks p.i., mean larval densities were 531 and 2,649 lpg, respectively, suggesting an extended persistence of intestinal worms. In seals with high larval density infections, the distribution of larvae in various muscles was uniform, but in one seal with a low larval density infection, predilection sites of larvae included muscle groups with a relative high blood flow, i.e. diaphragm, intercostal and rear flipper muscles. Trichinella-specific antibody levels, as measured by ELISA, increased during the 10 week experimental period. Infected seal muscle was stored at 5, −5 and −18 °C for 1, 4 and 8 weeks. Muscle larvae released from stored seal muscle by artificial digestion were inoculated into mice to assess viability and infectivity. Larvae from seal muscle 10 weeks p.i. tolerated −18 °C for 8 weeks but larvae from seal muscle 5 weeks p.i. tolerated only 1 week at −18 °C, supporting the hypothesis that freeze tolerance increases with the age of the host–parasite tissue complex. The expressed susceptibility to infection, extended production of larvae, antibody response and freeze tolerance of T. nativa in seals are new findings from the first experimental Trichinella infection in any marine mammal and suggest that pinnipeds (phocids, otariiids or walrus) may acquire Trichinella infection by scavenging even small amounts of infected tissue left by hunters or predators. [Copyright &y& Elsevier]

To evaluate infectivity for carnivores as well as other biological characteristics of the newly described Trichinella papuae, eight red foxes were experimentally infected with the parasite. Five weeks after inoculation, T. papuae larvae were recovered from nine different muscle types. The larvae recovered from muscle tissue were shown to be infective to mice, to have a very low tolerance to freezing, and to survive longer than the other Trichinella genotypes in decaying tissue up to 5 weeks after infection. [Copyright &y& Elsevier]

Abstract: A total of 72 specific pathogen-free (SPF) and Iberian pigs (three animals per group) were inoculated with 200, 1000 or 20,000 muscle larvae of T. spiralis, T. nativa, T. britovi and T. pseudospiralis. For each animal, the muscle larva burden was evaluated in nine muscle samples by digestion. The anti-Trichinella IgG kinetics in blood samples, taken twice prior and at days 5, 10, 15, 20, 25, 30, 40, 50 and 60 post-inoculation, and in muscle juice, obtained at necropsy, was evaluated by an ELISA using an excretory/secretory antigen. The mean larval recovery rate in SPF/Iberian pigs corresponded with the level of inoculum dose, and tongue, diaphragm and masseter were identified as predilection muscles. In SPF and Iberian pigs receiving 20,000 larvae of T. spiralis, an earlier seroconversion was detected from day 25 post-inoculation. At a 10-fold dilution, the muscle juice showed a good test agreement with blood serum. [Copyright &y& Elsevier]

Abstract: For the surveillance of trichinellosis, the digestion method is reliable but also labour intensive. The serological methods for the detection of Trichinella-specific antibodies using ELISA offer a sensitive and relatively specific alternative. For serological studies, sera or plasma from blood samples are the most common source of antibodies, but although the concentration of antibodies is approximately 10-fold lower, muscle fluid can be a good alternative particularly for testing of wildlife samples. In the present study, an indirect ELISA technique was evaluated on both sera and muscle fluids from experimentally infected foxes, pigs, and wild boars using both excretory/secretory (E/S) antigens and a synthetic glycan antigen, β-tyvelose. Although the synthetic antigen appears to be less sensitive than the E/S antigens, Trichinella-specific IgG antibodies were detected in both serum samples and muscle fluid samples from pigs, wild boars and foxes infected at levels which would be important for food safety or represent a significant reservoir for further transmission. [Copyright &y& Elsevier]