Molecular phylogenetics and diagnosis of soil and clinical isolates of Halicephalobus gingivalis (Nematoda: Cephalobina: Panagrolaimoidea), an opportunistic pathogen of horses.
Abstract: Phylogenetic relationships among six isolates of Halicephalobus gingivalis (Stefanski, 1954), a species with pathogenic potential in horses and humans, were evaluated using DNA sequences from the nuclear large-subunit ribosomal RNA (LSU rDNA) gene. Sequences from nematodes obtained from in vitro cultures (soil or clinical sources), or isolated from infected horse tissues, were compared. Gene sequences from a fatal equine clinical case from southern California and a free-living isolate recovered from southern California soil showed no fixed differences. Sequences from isolates representing two fatal equine cases from North America, one from Ontario, Canada and another from Tennessee also showed no fixed differences. In contrast, two equine cases from Tennessee had 18 fixed differences for this LSU region, the greatest observed among isolates from horses. Phylogenetic analysis of six Halicephalobus sequences and four outgroup taxa by maximum parsimony yielded one tree with five well-supported clades. This phylogeny did not group isolates of Halicephalobus strictly by region of geographic isolation or source of sample, and depicted one clinical and one soil isolate as sister taxa. These results confirm that free-living environmental isolates are potential sources of infection for horses. The phylogeny also reveals that diverse isolates can cause infections in horses within a relatively limited geographic region, and conversely that genetically similar sister taxa can be recovered from geographically distant localities. PCR primers that selectively amplify Halicephalobus DNA were designed and tested based on comparison of closely related nematodes as inferred from phylogenetic analysis.
Publication Date: 2003-09-18 PubMed ID: 13129534DOI: 10.1016/s0020-7519(03)00134-6Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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This research investigates the relation and origin of different isolates of the Halicephalobus gingivalis species, a potential pathogen to horses and humans, using DNA sequences from the nuclear large-subunit ribosomal RNA gene. It also makes efforts towards the development of PCR primers that can selectively amplify Halicephalobus DNA.
Study Methodology and Results
- The study compared DNA sequences from Halicephalobus gingivalis obtained from various sources such as from infected horse tissues, in vitro cultures from soil or clinical sources.
- The DNA sequences compared included those from a fatal equine clinical case and from a free-living isolate from the soil, both sourced from southern California. They were found to exhibit no fixed differences.
- The DNA sequences from two fatal equine cases, one from Ontario, Canada, and the other from Tennessee, North America, also exhibited no fixed differences.
- However, two equine cases from Tennessee revealed 18 fixed differences for the LSU region, which was the highest observed number among isolates from horses.
Phylogenetic Analysis and Findings
- A phylogenetic analysis carried out with six Halicephalobus sequences and four outgroup taxa revealed a tree with five well-supported clades.
- The phylogeny did not group the Halicephalobus isolates strictly according to the region of geographic isolation or the source of samples. For example, one clinical and one soil isolate were depicted as sister taxa.
- The results confirm that free-living environmental isolates could be potential sources of infection for horses.
- There are diverse isolates that can cause infections in horses within a relatively limited geographic region, and in contrast, genetically similar sister taxa can be recovered from geographically distant localities.
The Development of PCR Primers
- The study succeeded in designing and testing PCR primers that can selectively amplify Halicephalobus DNA. This was achieved based on a comparison of closely related nematodes as inferred from the phylogenetic analysis.
Cite This Article
APA
Nadler SA, Carreno RA, Adams BJ, Kinde H, Baldwin JG, Mundo-Ocampo M.
(2003).
Molecular phylogenetics and diagnosis of soil and clinical isolates of Halicephalobus gingivalis (Nematoda: Cephalobina: Panagrolaimoidea), an opportunistic pathogen of horses.
Int J Parasitol, 33(10), 1115-1125.
https://doi.org/10.1016/s0020-7519(03)00134-6 Publication
Researcher Affiliations
- Department of Nematology, University of California, Davis, CA 95616, USA. sandler@ucdavis.edu
MeSH Terms
- Animals
- Base Sequence
- DNA, Helminth / genetics
- DNA, Ribosomal / genetics
- Horse Diseases / diagnosis
- Horse Diseases / parasitology
- Horses
- Molecular Sequence Data
- Opportunistic Infections / diagnosis
- Opportunistic Infections / parasitology
- Opportunistic Infections / veterinary
- Phylogeny
- Polymerase Chain Reaction / methods
- Rhabditida / classification
- Rhabditida / genetics
- Rhabditida Infections / diagnosis
- Rhabditida Infections / parasitology
- Rhabditida Infections / veterinary
- Sequence Alignment
- Soil / parasitology
Citations
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