Viral load in trachea and eyelid tissue is comparable between M41K-Beau(S) and M41-K.

Samples of homogenised (A–C) eyelid and (D–F) trachea harvested on days 4 and 6 post-infection for experiment 1 and day 4 only for experiment 2 were titrated in ex vivo TOCs. Unfortunately, no tissue was available from day 6 in experiment 2 for this assay. Viral load in terms of CD₅₀ was calculated for each sample using the Reed-Muench method. Statistical differences were identified using a One-Way ANOVA followed by Tukey’s test for multiple comparisons and are highlighted by * (p<0.05) and ** (p<0.005). Of note, one sample of eyelid was damaged during extraction and there was not enough tissue available for this assay therefore in panel C there are only 4 birds for M41K-4/91(S).