Novel infectious bronchitis virus S1 genotypes in Mexico 1998-1999

Seventeen infectious bronchitis virus (IBV) field isolate's recovered from commercial broiler flocks in Mexico were identified by reverse transcription-polymerase chain reaction cycle sequencing of the S I gene, The isolates were obtained from broilers on farms from the neighboring states of Queretaro and San Luis Potosi in 1998 and 1999. Flocks had an ongoing history of bacterial-complicated respiratory disease with mortality rates as high as 28% in spite of receiving live vaccinations for Massachusetts and Connecticut strains of IBV. Sequence analysis of the S I gene identified two unique genotypes chat have been described, as of this time, only, in Mexico and thus appear to represent. strains indigenous to the country The Mex/1765/99 genotype was isolated from 64% (11/17) of the respiratory disease outbreaks. Three isolates (18%) were similar to the BL-56 genotype, a unique Mexican IBV strain observed initially in 1996. In addition to the two indigenous strains, three isolates (18%) were found to be the Connecticut genotype.