DNA analysis in the diagnosis of infection and in the speciation of nematode parasites.

DNA analysis is playing an increasingly important role in characterising and classifying nematode parasites. Though less emphasis has been placed on utilising DNA elements to study nematodes of veterinary importance, correct diagnosis is, nevertheless, critical to proper treatment and control. The genus Trichinella presents a particularly interesting problem since the level of classification within this genus remains unclear. Herein we discuss the application of DNA analysis to the diagnosis and speciation of the parasitic nematode Trichinella spiralis, where the study of cloned repetitive DNA elements and ribosomal RNA genes has led to significant advances in the understanding of the species-level systematics of this nematode. Despite advances in the recognition of multiple gene pools within the genus Trichinella, their taxonomic level is still uncertain because of insufficient knowledge regarding intraspecific variation within this genus. The utility of mitochondrial DNA and ribosomal DNA sequence analysis in studying the phylogeny and evolutionary history of parasites within this genus is also discussed.