Single-strand conformation polymorphism (SSCP) analysis as a new diagnostic tool to distinguish dorsal-spined larvae of the Elaphostrongylinae (Nematoda: Protostrongylidae) from cervids

Single-strand conformation polymorphism (SSCP) was used to genetically differentiate morphologically indistinguishable first-stage larvae (L1) of the six species of elaphostrongyline nematodes. A partial fragment (317–336 bp) of the first internal transcribed spacer (pITS-1) plus 5′ flanking region (76 bp of the 18S gene) of the nuclear ribosomal DNA (rDNA) was amplified from individual L1 of known identity and subjected to SSCP. The results showed that the four species of elaphostrongylines found in North American cervids, Parelaphostrongylus tenuis, P. andersoni, P. odocoilei and Elaphostrongylus rangiferi, could be distinguished from one another based on their distinct (i.e. species-specific) SSCP profiles. In addition, E. alces, a species that occurs in moose in Fennoscandinavia, also had a distinct SSCP profile with respect to the other species of elaphostrongylines. However, the SSCP profiles of E. cervi could not be distinguished from those of E. rangiferi because of a lack of interspecific sequence differences in this region of the ITS-1. The distinct SSCP profiles for the other species were consistent with the interspecific differences in ITS-1 sequences, which ranged from 2 (between P. tenuis and P. andersoni) to 59 bp (between genera). The pITS-1 SSCP approach was also used to identify unknown elaphostrongyline L1 from different hosts and localities in North America. The ability to distinguish between L1 of the four elaphostrongyline species that occur in North American cervids has important diagnostic and epidemiological implications.