Quantitative DNA metabarcoding reveals species composition of a macrocyclic lactone and pyrantel resistant cyathostomin population in the UK
Bibliographic record
Abstract
Cyathostomins are the most abundant equid endoparasites globally. There are approximately fifty cyathostomin species and, whilst they occupy distinct niches within the large intestine, they are generally considered to share similar characteristics in terms of pathogenicity and response to drug treatment. There are three classes of anthelmintic licensed in the UK to treat cyathostomins (benzimidazoles, tetrahydropyrimidines and macrocyclic lactones) and cases of resistance have been documented for all classes. Previously, faecal egg count reduction tests (FECRT) on four UK Thoroughbred studs revealed multidrug resistant cyathostomins on one stud (A), with evidence of resistance to the macrocyclic lactones (MLs) ivermectin (IVM) and moxidectin (MOX), and to pyrantel (PYR). The remaining three studs (B-D) lacked resistance to IVM and MOX but had a shortened egg reappearance period post treatment. To determine whether specific species could be associated with the observed resistance and shortened egg reappearance period, strongyle eggs collected from between six and 15 individual horses per stud were copro-cultured to third larval stage (L3), before and after anthelmintic treatment, over a three-year timeframe (2021–2023). Quantitative DNA metabarcoding of the ITS-2 region was carried out on all samples. On stud A, single but differing species were found to be responsible for ML and pyrantel resistance in yearlings, Cyathostomum catinatum and Cylicocyclus nassatus, respectively. On studs B-D, with shortened egg reappearance periods, species composition remained largely unchanged post treatment. This study is the first to quantitatively profile cyathostomin species composition pre- and post-treatment in a multidrug resistant population in the UK, revealing that resistance in cyathostomins was species specific. This raises the question of whether these species may be responsible for ML and PYR resistance more widely and indicates that anthelmintic resistance in cyathostomins may not be a multi-species phenomenon. • ITS-2 metabarcoding revealed cyathostomin species proportions pre- and post-drug treatment on four studs. • Cya. catinatum comprised between 97.5 and 99.5% of eggs shed in the ML-resistant population two weeks post ML treatment. • Cyl. nassatus was more abundant after PYR treatment in the PYR-resistant population. • Non-ML resistant populations had no significant changes in species abundance post treatment. • A shortened ERP is associated with the presence of multiple cyathostomin species post treatment.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".