The scores of clinical signs of the pigs after challenge and lung lesions were recorded at 21 dpc.

Lung lesions were also recorded when pigs died during the 21 days post challenge a. aWithin each column, values followed by different letters (A, B, C and D) were significantly different (P<0.05). bClinical signs of each pig were evaluated daily after challenge. The results were expressed as mean±standard error. cAverage lung scores were recorded. The results were expressed as mean±standard error.