Development of a single larva microsatellite analysis to investigate the population structure of Trichinella spiralis.

Trichinella spiralis is the most important etiological agent of human trichinellosis. It has a cosmopolitan distribution and is transmitted to humans mainly through the consumption of pork. In nature, transmission occurs among animals through the ingestion of an infected carcass by one or more hosts. Microsatellite markers have provided insight into how T. spiralis dispersed geographically over its evolutionary history. The objectives of the present study were to develop microsatellite markers capable of differentiating single larvae for investigating the inter- and intra-specific population structure of T. spiralis and to determine their usefulness as genetic markers to study transmission mechanisms of this zoonotic parasite. A panel of 48 larvae derived from each of 22 distinct isolates originating from the Americas, Asia and Europe, were investigated. A total of 27 alleles were detected in these samples using seven new markers. The sequences of the amplified fragments containing the microsatellites support the homology of the amplified products and validate their use for genetic population studies. We documented the first known occurrence of a genetically variable larval admixture, indicating that more than two adults gave rise to the ensuing population of this host's muscle larvae. Globally, T. spiralis was observed to harbor less genetic variation than other nematodes, a result consistent with previous assays of nuclear and mitochondrial variation.