Submitted to: Parasite
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/19/2002
Publication Date: 1/28/2002
Citation: Interpretive Summary: Trichinellosis is a globally distributed zoonotic disease caused by the ingestion of raw or undercooked meats harboring parasites of the genus Trichinella. Disease eradication is compounded by the limitless host specificity of Trichinella larvae which are capable of infecting nearly all carnivores and omnivores. Though the incidence of human Trichinellosis originating from swine has been on the decline in recent years in the United States and in countries of the European Union, the occurrence of this disease emanating from sylvatic genotypes and hosts remains a major source of human infection in these countries.Within most parasite genera, distinct morphological and/or biological characters exist among the species that permit differentiation and proper classification. However, the absence of distinguishing morphological characters and the overlapping nature of the biological characters within the genus Trichinella, make these traits unsuitable for proper diagnosis. Consequently, identification and classification of species within this genus must rely heavily upon molecular and biochemical data. Herein we develop a multiplex PCR test based upon rDNA repeat sequences that is capable of ;1) differentiating all well-defined genotypes of Trichinella including three genotypic isolates of T. pseudospiralis; 2) circumventing the need for external PCR controls, and; 3) distinguishing single larvae using nested PCR.This work will greatly facilitate the elucidation of parasites within this genus for epidemiological studies as well as permit species diagnosis from host biopsies.
Technical Abstract: In recent years, the discovery of many non-encapsulated isolates of Trichinella, designated Trichinella pseudospiralis and the identification of a new non-encapsulated species, Trichinella papuae, has revealed that the biomass of the genus Trichinella does not only include the well known encapsulated species (T. spiralis, T. nativa, T. britovi, T.murrelli, and T. nelsoni) but also ncludes geographically disseminated, non-encapsulated species that represent important biological entities in the genus. Larvae of the first stage (L1) of both non-encapsulated and encapsulated species are able to penetrate the muscle cell and induce a dedifferentiation of this cell. But following this point in the parenteral cycle, non-encapsulated and encapsulated species diverge with respect to their developmental strategies where L1 of encapsulated species are able to induce the nurse cell to synthesize collagen, unlike non-encapsulated larvae which do not induce collagen production. The presence or absence of a collagen capsule is of great importance in the natural cycle of these parasites in that it allows the encapsulated larva to survive to substantially longer periods of time and therefore remain infective even within putrefied muscle tissue. This as well as isoenzyme and genetic data suggest that the genus Trichinella be split into 2 distinct genera.