The authors review the major biological, biochemical, and molecular characters that are used to distinguish the seven Trichinella species (T. spiralis, T. nativa, T. britovi, T. pseudospiralis, T. ...murrelli, T. nelsoni, T. papuae) and three genotypes whose taxonomic status is yet uncertain (T-6, T-8, T-9). A comparison of host specificity, morphology, reproductive abilities, nurse cell development and freeze resistance is presented, along with useful biochemical and molecular markers. Finally, this information is used to construct a diagnostic key for the species. A phylogenetic classification of the species is needed.
We report the use of six oligoprobes designed from intergenic spacer region sequences to identify fourth-stage larvae (L4) of the tribe Cyathostominae. Oligoprobes were designed for identification of ...the following species:
Cylicocyclus ashworthi,
Cylicocyclus nassatus,
Cylicocyclus insigne,
Cyathostomum catinatum,
Cylicostephanus goldi, and
Cylicostephanus longibursatus. A seventh probe was designed as a positive control to identify all these members of the Cyathostominae. The intergenic spacer region was amplified by PCR using conserved primers. Initially, three oligoprobes were used in Southern blot analysis. To facilitate high-throughput identification, these and a further four oligoprobes were developed for use in a PCR–ELISA. All probes were validated for their ability to detect cyathostomin PCR products in the PCR–ELISA, using DNA from morphologically identified adult parasites. Initially, 712 L4 were isolated from the diarrhoeic faeces from horses (
n=17) with clinical larval cyathostominosis. PCR products from 522 of these L4 were subjected to analysis, with 413 L4 being identified as one of the aforementioned species. With reference to individual species analysis, 28.5% of the 522 L4 were identified as
C. longibursatus, 25.7% as
C. nassatus, 15.9% as
C. ashworthi, 7.3% as
C. goldi and 1.7% as
C. catinatum. No L4 were identified as being
C. insigne species. When L4 within faeces from individual horses were compared, no sample was found to comprise parasites of one species. The least number of species identified in a single sample was two. This study suggests that clinical larval cyathostominosis is predominantly caused by mixed-species infections.
The results of an international collaborative effort to prepare a recommended list of scientific names for the small strongyles (Nematoda: Strongyloidea: Cyathostominea) of horses, donkeys and zebras ...are reported. Fifty-one valid species are recognized in 13 genera, including
Cyathostomum,
Coronocyclus,
Cylicodontophorus,
Cylicocyclus,
Cylicostephanus,
Skrjabinodentus,
Tridentoinfundibulum,
Petrovinema,
Poteriostomum,
Parapoteriostomum,
Hsiungia,
Cylindropharynx and
Caballonema. In addition, 42 other species level names are listed as synonyms of the 51 recognized species or as species inquirendae (10 species) or nomen nudum (one species). Numerous annotations provide information on the nomenclatural and systematics history, current status and additional studies needed.
The efficacy of five daily fenbendazole (FBZ) treatments was tested against benzimidazole-resistant cyathostomins in naturally infected horses (n=13). Horses were treated with pyrantel embonate (PYR) ...to remove adult strongyles followed, 7 days later, by a 5-day course of FBZ. The PYR treatment produced an average faecal egg count reduction of 98%. All samples were negative by faecal egg count 7 days after the start of the FBZ treatment. Positive egg counts were observed from 28 days after the start of FBZ treatment and all horses displayed positive faecal egg counts by 77 days after treatment. Strongyle eggs were harvested from the faeces of the horses prior to treatment and then weekly from 42 to 70 days post-treatment. DNA was obtained from eggs in groups of ten. A PCR-ELISA, based on species-specific differences in intergenic DNA sequences, was used to identify the presence of six cyathostomin species. In pre-treatment samples, Cyathostomum catinatum was detected in nine out of the 13 horses and Cylicostephanus longibursatus, Cylicostephanus goldi and Cylicocyclus nassatus, were found in samples from eight animals. Cylicocyclus ashworthi and Cylicocyclus insigne were not detected pre-treatment. After anthelmintic treatment, C. catinatum and C. longibursatus were most frequently detected, followed by C. nassatus, C. goldi and C. ashworthi. C. insigne was detected at only one time point in a sample from a single horse.
In December 2001, the routine inspection of a wild boar intended for human consumption revealed the presence of
Trichinella ssp. larvae. Biological, morphological and genetic analyses demonstrated ...the parasite to be
Trichinella pseudospiralis. This is the second report of
T. pseudospiralis in the United States and the first report of the parasite in a food animal species in the U.S.
Terminology for common names for the Tribe Cyathostominea (cyathostomins), and disease caused by the nematodes (cyathostominosis), were recommended to replace the previously used names cyathostomes ...and cyathostomosis, which are ambiguous, inaccurate or synonymous, by the Third Internal Workshop on the Systematics of Cyathostominea of Horses, held in Stresa, Italy, 28 August 2001. The progress by this international working group at three workshops is reviewed briefly and a list of publications is provided. Included are an annotated checklist by genus and species of 93 species level names and the recognition of 52 species, redescriptions of seven species, and the description of one new species. Upon petition by workshop participants, the International Commission on Zoological Nomenclature placed
Cyathostomum tetracanthum Mehlis, 1831 on the “Official List of Specific Names in Zoology”, ending more than a century of controversy over the names of cyathostomins. Some progress is described in molecular and morphological systematics and in the development of diagnostic molecular probes. A revised identification key is being prepared to the 52 species of the Tribe Cyathostominea.
Here, we report evaluation of five oligoprobes designed from intergenic spacer (IGS) region sequences for identification of cyathostomin species. Oligoprobes were designed for identification of
...Cylicocyclus ashworthi,
Cylicocyclus nassatus,
Cylicostephanus longibursatus,
Cylicostephanus goldi and a fifth probe designed to identify all members of this tribe. PCR amplification of IGS DNA from 16 cyathostomin species allowed sequence comparison and identification of four putative species-specific probes. Southern blotting of amplified products from 16 species showed that all probes were species-specific. The fifth probe recognised all 16 cyathostomin species but did not bind to members of the genus
Strongylus. Furthermore, these probes were used to identify individual infective L3, eggs and L4 indicating that they will be invaluable to furthering the study of the epidemiology and pathogenesis of these important equine nematodes.
The nucleotide sequences of the first and second internal transcribed spacers of nuclear ribosomal DNA were determined for adults of
Cylicostephanus minutus from different geographical origins. The ...lengths of first and second internal transcribed spacer sequences ranged from 370 to 372 bp and 215 to 216 bp, respectively. Pairwise sequence comparisons revealed that some individuals of
C. minutus had identical first and second internal transcribed spacer sequences, whereas others differed by 3.0% and 7.4% in their first and second transcribed spacers, respectively. Some individuals with sequence differences originated from the same host. The levels of difference within
C. minutus were higher than that between the morphologically distinct species,
Cylicostephanus goldi and
Cylicostephanus longibursatus (0.8% for the first internal transcribed spacer and 3.8% for the second internal transcribed spacer). The data provide support for the proposal that
C.minutus represents a complex of at least two species. In order to study the population genetic structure of
C. minutus, a PCR-linked single-strand conformation polymorphism technique was also established.
Three nucleotide data sets, one nuclear (ITS-2) and two mitochondrial (COI and l-rRNA), have been investigated in order to determine relationships among species of Strongylinae and Cyathostominae, ...intestinal parasites of the horse. The data exhibited a strong mutational bias towards A and T and in the COI gene, silent sites appeared to saturate rapidly partly due to this substitution bias. Thus, the COI gene was found to be less phylogenetically informative than the l-rRNA and ITS-2 genes. Combined analysis of the l-rRNA and ITS-2 genes supported a monophyletic clade of the cyathostomes with Tridentoinfundibulum gobi, which had previously been classified as a nematode of' uncertain origin'. The Strongylinae grouped consistently outside the clade containing the cyathostomes and T. gobi. Molecular analysis failed to provide strong evidence for the separation of cyathostomes into classical genera, as previously defined by morphological classification.
PDF
