The pathogenesis of necrotic enteritis in chickens: what we know and what we need to know: a review
Bibliographic record
Abstract
This review summarizes advances in understanding the pathogenesis of necrotic enteritis of chickens caused by netB-positive Clostridium perfringens. The discovery of NetB as the essential toxin trigger for the disease was followed by recognition that it forms part of a large plasmid-encoded 42 kb pathogenicity locus (NELoc-1). While the locus is critical for toxin production, it likely has additional functions related to colonization and degradation of the mucus barrier, which are essential both to multiplication and to bringing NetB close to the intestinal epithelium. Two "chitinases" (glycoside hydrolases (GHs)) present on NELoc-1 are predicted to be involved in mucin degradation, as is the large carbohydrate-binding metalloprotease, shown to be involved in mucinase activity in other clostridia. A second pathogenicity locus found in netB-positive C. perfringens, NELoc-2, also encodes a GH likely involved in mucin degradation. Upon reaching a sufficient cell density on the intestinal mucosa, the Agr-like quorum-sensing system is triggered, which in turn up-regulates the VirR/VirS regulon. This regulon includes NetB. Where NetB initiates damage is unresolved, but it may be deep in the intestinal mucosa, rather than superficially. As the disease progresses, C. perfringens line what remains of the intestinal epithelium in large numbers. This likely involves a number of different bacterial adhesins, including additional NELoc-1-encoded bacterial surface proteins, some of which may adhere to epithelial cell ligands exposed by bacterial sialidases. Further studies of the pathogenesis of necrotic enteritis should lead to development of novel ways to control the infection.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".