Table 1.
Effects of anthelmintic treatment, worm resistance phenotype, and duration of infection on BTB severity quantified by gross and histolopathological examination of the lungs and respiratory lymph nodes
| Variable | Model type | n | Anthelmintic treatment | Resistance phenotype | Duration of infection | Treatment × resistance phenotype | Treatment/resistance phenotype effect direction |
| Lungs | |||||||
| No. of positive lesions | Negative binomial GLM | 34 | — | 1.079+ | 0.0024* | — | (Low: +) |
| Mineralization | Binomial GLM | 29 | — | — | 0.0022+ | — | |
| Fibrosis | Binomial GLM | 29 | −2.996* | 20.33 | — | — | Untreated: − |
| MNGC | Binomial GLM | 29 | — | 3.00* | 0.0039* | — | Low: + |
| Stage | Ordinal regression | 29 | — | 1.99* | 0.003* | — | Low: + |
| Lymph nodes | |||||||
| No. of positive respiratory nodes | Negative binomial GLM | 34 | 2.12** | 1.84+ | 0.0045* | — | Untreated: + (Low: +) |
| Mineralization | Binomial GLM | 34 | −0.287 | −18.06 | — | 19.85 | |
| Caseous | Binomial GLM | 34 | — | — | — | — | |
| MNGC | Binomial GLM | 34 | 2.602** | — | — | — | Untreated: + |
| Granuloma score | Ordinal regression | 34 | 2.45** | — | — | — | Untreated: + |
| Stage | Ordinal regression | 34 | 2.505** | — | — | — | Untreated: + |
In the lungs, severity was measured as the number of BTB lesions and MNGC formation (indicators of the host’s ability to control bacterial infection), lesion stage (indicator of the length and severity of infection), and the presence of mineralization and fibrosis (indicators of the degree of tissue damage within lesions). In the lymph nodes, severity was measured as the number of respiratory nodes with BTB lesions (indicator of disease dissemination), the RPLN granuloma score and stage (indicators of the distribution and severity of infection), and mineralization, caseous necrosis, and MNGC formation (indicators of the degree of tissue damage within RPLN lesions). Full models of the structure: Y ∼ anthelmintic treatment + resistance phenotype + infection duration + treatment × resistance phenotype were run for each variable and final models were selected using AIC-based model simplification. Values represent estimates from the final models. Significant factors appear in bold (significance codes: **P < 0.01, *P < 0.05, +P < 0.1). Effect description summarizes the direction of each significant treatment and resistance phenotype effect; trends appear in parentheses.