VARIATIONS IN MICROSATELLITE SEQUENCES PROVIDE EVIDENCE FOR POPULATION DIFFERENCES AND MULTIPLE RIBOSOMAL GENE REPEATS WITHIN TRICHINELLA-PSEUDOSPIRALIS

Enzymatic amplification of expansion segment 5 sequences within domain IV of the large subunit ribosomal DNA generated distinct results amon g geographical isolates of Trichinella pseudospiralis from Russia, Nor th America, and Australia from both avian and mammalian hosts. Discret e, multiple DNA fragments ranging in approximate size from 285 to 360 bp were observed within and among each of the isolates tested. Polymer ase chain reaction performed on individual adult parasites from each i solate resulted in multiple DNA fragments that were comparable to thos e generated from pooled genomic DNA. Sequence analysis of cloned, repr esentative amplified fragments demonstrated that fragment length varia tion resulted primarily from the dinucleotide (TG)(n) and trinucleotid e (TGC)(n) microsatellite repeats present within the expansion segment . Results are consistent with both population differences within the s pecies as well as the presence of multiple alleles of the large subuni t ribosomal RNA genes within individual parasites.