Submitted to: Electrophoresis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 3, 2004
Publication Date: October 18, 2004
Citation: Gasser, R.B., Hu, M., Abs El-Osta, Y.G., Zarlenga, D.S., Pozio, E. 2004. Non-isotopic single-strand conformation polymorphism analysis of sequence variability in ribosomal dna expansion segments within the genus trichinella (nematoda: adenophorea). Electrophoresis. 25(20):3357-64.
Interpretive Summary: Trichinellosis is a disease of major public health significance, caused by parasitic nematodes of the genus Trichinella. Human infections have seen a world-wide resurgence eminating from both domestic and wild hosts. The diagnosis of trichinellosis and investigating the genetic make up of Trichinella populations is central to studying and understanding host-parasite relationships, transmission patterns and the development of control strategies. In the present study, we report a simple, PCR-based approach for the analysis of genetic variation within and among the currently recognized species and genotypes of Trichinella, by targetting the highly variable expansion segment 5 region of the ribosomal DNA. We also examine the genetic relationships among these species and genotypes by evaluating sequence variation within less variable regions of the same gene. This information will help identify local sources of infection, help prevent repopulating domentic livestock with Trichinella species, and provide information as to which sylvatic hosts are high risk sources of human infection in any given geographical locality.
A non-isotopic single-strand conformation polymorphism approach was established to 'fingerprint' sequence variability in the expansion segment 5 (ES5) of domain IV and the D3 domain of nuclear ribosomal DNA within and/or among isolates and individual muscle (first-stage) larvae representing all currently recognized species/genotypes of Trichinella. In addition, phylogenetic analyses of the D3 sequence data set, employing the three different tree-building algorithms, examined the relationships among all of them. These analyses showed strong support that the encapsulated species T. spiralis and T. nelsoni formed a group to the exclusion of the other encapsulated species T. britovi and its related genotypes Trichinella T8 and T9 and T. murrelli, and T. nativa and Trichinella T6, and strong support that T. nativa and Trichinella T6 grouped together. Also, these eight encapsulated members grouped to the exclusion of the non-encapsulated species T. papuae and T. zimbabwensis and the three representatives of T. pseudospiralis investigated. The findings showed that non-encapsulated species constitute a complex group which is distinct from the encapsulated species and supported the present hypothesis that encapsulated Trichinella group external to the non-encapsulated forms, in accordance with independent biological and biochemical data sets.