Influence of temperature of incubation on chicken embryo tracheal organ cultures and chick embryos infected with strains of avian infectious bronchitis virus.

The ciliostatic and embryo lethal effect of four strains of avian infectious bronchitis virus (IBV) were observed at two different incubation temperatures. In organ cultures, nephrosis-producing IBV strains (GN-2 and M-41) were slightly more ciliostatic and respiratory strains (Beaudette and Kita-1/Tokushima) less ciliostatic at 40.5°C than at 37°C. Mortality of chicken embryos infected with the GN-2, M-41 and Kita-1/Tokushima strains was greater at 40.5°C than at 37°C, while the reverse was true of the Beaudette strain which caused no embryo mortality at 40.5°C. The Beaudette strain of IBV was the only one which could not be recovered from the kidneys of young chickens four days after infection. These results indicate that the different IBV strains may show variation in virulence at different temperatures in ovo and in organ cultures and this may be a reflection of the virulence and tropism for chickens.