Comparison of the pathogenicity of QX-like, M41 and 793/B IBV strains from different pathological conditions.
Résumé
Five QX-like strains, isolated from different field outbreaks and two reference IBV strains of well known serotype (M41 and 793/B) were used in this study to investigate and compare their pathogenicity on one day old SPF chickens. Ability of the strains to inhibit trachea epithelial cilium activity, to induce immune response, to replicate and to cause histopathological lesions in designated organs were followed by repeated samplings during a period of 42 days post-infection. By comparing the results of the strains, clear differences in pathogenicity and in organ distribution of the three serotypes were found. 793/B had the least capacity to invade the investigated organs, while it produced good humoral response as measured by ELISA. QX-like strains generally replicated in higher titres, although differences were found among the five strains, in the pathogenicity and affinity to different organs. The Chinese isolate of QX-like strain proved to cause the more severe lesions and induce the highest antibody titres as well. Severe kidney damage and dilation of the oviduct were the prominent lesions, which could be related to these strains, although remarkable virus replication and histopathological lesions were not detected in the oviduct.
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