Vaccination with M41K-Beau(S) or M41R-Beau(S) protects against M41-CK challenge.

Groups of 30 SPF RIR chicks were vaccinated at 8 days old with 10⁴ PFU of either M41K-Beau(S) or M41R-Beau(S) or mock vaccinated with PBS via the intraocular and intranasal route. At 27 days post-vaccination chickens were either challenged with 10⁴ M41-CK or mock challenged with PBS also via the intranasal and intraocular route. Clinical signs including snicking (A and B) and rales (C and D) were observed from day 3 to day 7 post-vaccination and day 3 to 7 post-challenge. Trachea were extracted from six randomly selected birds on day 4 post-vaccination (E), day 4 and 6 post-challenge (F) and sectioned into 10 x 1 mm rings. Each ring was analysed under a light microscope and assigned a score between 1 and 4 depending on the proportion of cilia beating. 1 = 25% beating, 2 = 50%, 3 = 75%, 4 = 100%. Each data point represents the average percentage ciliary activity of each bird. Error bars represent SD. Statistical differences were assessed using a Two-Way ANOVA followed by Tukey’s test for multiple comparisons and are highlighted by **** (p<0.0001).