Molecular approaches for studying ascaridoid nematodes with zoonotic potential, with an emphasis on Toxocara species

Species-specific identification of ascaridoid nematodes at any developmenta l stage is a prerequisite for detailed investigation of the life cycles, sy stematics and epidemiology of this important group, and is also crucial for the diagnosis of associated infections. The morphological identification o f some species and/ or their larval stages can, however, present considerab le difficulty. Recently, PCR-based methods, using genetic markers in the in ternal transcribed spacers (ITS) of ribosomal DNA, have been shown to provi de reliable alternatives to more traditional methods for the specific ident ification of nematodes. This article provides an account of recent research on the development of PCR-based methods (utilizing ITS sequences) for the specific identification of ascaridoid nematodes of zoonotic potential, for the diagnosis of infections, and for the analysis of genetic variation with in and among individual nematodes and their populations. Prospects for usin g these diagnostic and analytical tools to investigate epidemiological and population genetic questions relating to ascaridoid parasites are also disc ussed.