[Biology, species biodiversity and distribution of Trichinella nematodes]

Abstract

From the time of the discovery of Trichinella larvae in 1835 until the middle of the next century it was commonly assumed that all trichinellosis was caused by a single species Trichinella spiralis. This species is an intracellular parasite in both a larva and an adult stage. The L1 larvae live in a modified skeletal muscles. The adult worms occupy a membrane-bound portion of columnar epitelium, living as intramulticellular parasite. More than century later T. spiralis have been reported from more than 150 different naturally or experimentally infected hosts and demonstrated worldwide distribution in domestic and/or sylvatic animals. Up to date, Trichinella genus comprised eight species (T. spiralis, T. nativa, T. britovi, T. murrelli, T. nelsoni, T. pseudospiralis, T. papuae and T. zimbabwensisi) and three additional genotypic variants that have not yet to be taxonomically defined (T6, T8, T9). Molecular markers revealed that Trichinella T6 is related to T. nativa, Trichinella T8 related to T. britovi. Two main clades are recognized in the genus Trichinella: the first encapsulated in host muscle tissue and the second--non-encapsulated. In this paper the history of Trichinella spp. discovery, their life cycle, taxonomy and phylogeny have been reviewed.