Trichinella species and genotypes

Authors: Zarlenga, Dante; Thompson, Peter; POZIO, EDOARDO - Istituto Superiore Di Sanita

Submitted to: Research in Veterinary Science
Publication Type: Review Article
Publication Acceptance Date: 8/28/2020
Publication Date: 9/1/2020
Citation: Zarlenga, D.S., Thompson, P.C., Pozio, E. 2020. Trichinella species and genotypes. Research in Veterinary Science. 133:289-296. https://doi.org/10.1016/j.rvsc.2020.08.012.
DOI: https://doi.org/10.1016/j.rvsc.2020.08.012

Interpretive Summary: Trichinella spiralis has historically been deemed “the pig parasite” owing to its initial classification within a monospecific genus. However, in recent years, the genus has expanded to include 10 distinct species and at least 3 different genotypes whose taxonomic status remains unstipulated. In contrast to T. spiralis, however, most of these sylvatic species and genotypes do not infect pigs well. Inasmuch as morphological characters cannot be used to define species within this genus, earlier classifications were based upon host and geographical ranges, biological characters, and the presence or absence of a cyst that encapsulates the muscle stage larvae. Later, isoenzymes, DNA gel fragmentation patterns and DNA probes were used to help in identification and classification. Today, amidst the “-omics” revolution, new molecular and biochemical-based methodologies have improved detection, differentiation and characterization at all levels including worm populations. These efforts have discernably expanded immunological, epidemiological, and genetic studies resulting in better hypotheses on the evolution of the genus, and on global events, transmission cycles, host associations, and biogeographical histories that contributed to its cosmopolitan distribution. This review covers that history as well as the most recent knowledge available on the taxonomy, phylogeny, epidemiology and biochemistry that define this genus in the 21st century. The information will be of interest to veterinarians, wildlife biologists, swine producers, food safety experts, and consumers.

Technical Abstract: Trichinella spiralis has historically been deemed “the pig parasite” owing to its initial classification within a monospecific genus. However, in recent years, the genus has expanded to include 10 distinct species and at least 3 different genotypes whose taxonomic status remains unstipulated. In contrast to T. spiralis, however, most of these sylvatic species and genotypes do not infect pigs well. Inasmuch as morphological characters cannot be used to define species within this genus, earlier classifications were based upon host and geographical ranges, biological characters, and the presence or absence of a cyst that encapsulates the muscle stage larvae. Later, isoenzymes, DNA gel fragmentation patterns and DNA probes were used to help in identification and classification. Today, amidst the “-omics” revolution, new molecular and biochemical-based methodologies have improved detection, differentiation and characterization at all levels including worm populations. These efforts have discernably expanded immunological, epidemiological, and genetic studies resulting in better hypotheses on the evolution of the genus, and on global events, transmission cycles, host associations, and biogeographical histories that contributed to its cosmopolitan distribution. Reviews of this sort are best begun with a background on the genus; however, efforts will divert to the most recent knowledge available on the taxonomy, phylogeny, epidemiology and biochemistry that define this genus in the 21st century.