Fig 1.
Clinical signs (A) and pathologic lesions (B) observed during the experiment. (A) Non-specific symptoms include depression, ruffled feathers, and closed eyes. Lameness includes all stages from mild to completely paralyzed. (B) Spondylitis FTV = abscess was found at the free thoracic vertebra, FH = femoral head. N = 147 per group in the EC-infected groups, N = 143 in the control group.
Fig 2.
(A) Clinical signs of the septic phase of the EC-infection (study day 15, EC14_low). (B) Pericarditis due to EC (study day 25, EC14_low). (C) Clinical signs of the skeletal phase of the EC-infection. This broiler was sitting on hocks and unable to walk (study day 29, EC14_low). (D) Spondylitis at the FTV (arrow). The vertebral column was removed and split sagittally to expose the lesion (study day 30, EC14_high). (E) Clinical signs of the skeletal phase of the EC-infection. This broiler was lame due to femoral head osteomyelitis (study day 52, EC14_high). (F) Femoral head osteomyelitis (arrow). The femoral head was exarticulated by using a sterile scalpel and split sagittally (study day 43, EC14_low). EC was isolated in pure culture from the lesions in pictures B, D, and F.
Table 1.
EC-positive euthanized or dead birds at irregular necropsies.
Fig 3.
Bacteriological examination via culture and real-time PCR.
(A) EC-positive birds on culture in %. (B) EC-positive birds in real-time PCR in %. Ct values below 36 were considered positive. Different letters indicate significant differences between the groups per organ (p ≤ 0.05). Comparison between the groups was made for each organ by using Fisher’s exact test. p-value adjustments for multiple testing were performed by using the Bonferroni-Holm correction method. Comparison between the groups was not done for culture results of the FTV and the femoral heads, because these samples were only taken when gross lesions were detected. N = 147 per group (EC-infected groups), N = 143 in the control group. FTV = free thoracic vertebra, FH = femoral heads.
Fig 4.
Comparison of bacteriological examination of the spleen via culture and real-time PCR.
EC-positive spleens in groups EC14_low and EC14_high are shown per study day in %. Ct values below 36 were considered positive. All birds in the control group were found to be EC-negative in both detection methods. According to the Kappa coefficient, there was at least a substantial agreement (κ > 0.61) on the EC-status at all study days and McNemar’s test revealed no significant differences in distribution of results. N = 20 per group and study day.
Table 2.
Kappa coefficient and McNemar’s test for comparison of different detection methods.
Fig 5.
Samples were analyzed via real-time PCR, and Ct values below 36 were considered positive. Different letters indicate significant differences between the groups per study day (p ≤ 0.05). Comparison between the groups was made for each study day by using Fisher’s exact test. p-value adjustments for multiple testing were performed by using the Bonferroni-Holm correction method. N = 20 per group and study day.