Retrospective Comparison of Polymerase Chain Reaction and Culture-Based Identification for Diagnosis of Microsporum canis and Trichophyton Spp. in Shelter Cats and Dogs
Bibliographic record
Abstract
Introduction: Canine and feline dermatophytosis is challenging to manage in shelter settings because of its transmissibility, potential for zoonosis and labour-intensive treatment. An efficient and accurate initial diagnostic plan is essential to confirm infection, prevent outbreaks and ensure public safety. While quantitative polymerase chain reaction (PCR) has gained attention for its rapid turnaround time, studies have shown variable sensitivity. This study aimed to assess the performance of PCR in detecting Microsporum canis and Trichophyton spp. in shelter cats and dogs when compared to culture-based identification. Methods: Between 1 June 2015 and 10 January 2023, 125,939 cats and dogs entered 34 sheltering locations in coastal Western Canada. Of these, 246 animals (48 dogs, 198 cats) had both culture and PCR results, and sufficient records for analysis. Toothbrush samples were collected for dermatophyte test medium (DTM)/enhanced sporulation agar (ESA) bi-plates at a central shelter location and submitted for PCR at a referral laboratory before treatment was initiated. The diagnostic accuracy of PCR was evaluated using the reference standard of a 14-day culture result combined with P-scoring, a semi-quantitative method to assess DTM culture colonies. Results: Culture readings identified 72/246 (29.27%) lesional animals as positive (63 cats [31.81%] and 9 dogs [18.75%]). PCR demonstrated an overall sensitivity of 86.1% and specificity of 94.8% for both animal species combined. PCR for M. canis showed a sensitivity of 86.4% and a specificity of 97.8%, while PCR for Trichophyton spp. showed a sensitivity of 84.6% and specificity of 97.9%. DTM/ESA culture was highly efficient, with positive results available within 7 days for most cases (59/63 cats [93.6%] and 9/9 dogs [100%]). Conclusion: The variability in dermatophyte PCR sensitivity across recent studies highlights the risks of reliance on PCR as a sole diagnostic tool for suspect animals, especially when considering the demonstrated efficacy of in-house culture.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.005 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".