RESUMEN
Infectious bronchitis virus (IBV) isolates recovered in Russia, Ukraine, and Kazakhstan between 2007 and 2010 were subjected to molecular characterization and compared with those isolated a decade ago. The IBV genome was detected in 202 out of 605 field samples from chickens with various clinical signs. Partial sequencing of the S1 gene revealed 153 vaccine strains and 49 field isolates of several genetic groups. Massachusetts, 793/B and D274 remained the predominant IBV genotypes along with QX, whereas B1648, Italy-02, Arkansas and variants accounted for about 12% of the total number. Three IBVs contained recombinant S1 gene sequences comprising genome fragments of QX-type field isolates and vaccine strains H120 (UKR/02/2009) or 4/91 (RF/03/2010), and vaccine strains H120 and D274 (RF/01/2010). The results of the present study showed a significant decline in prevalence of variant IBVs and a further spread of QX-type isolates in commercial chicken flocks in Russia as compared with the 1998 to 2002 data.
Asunto(s)
Proteínas de la Cápside/genética , Pollos/virología , Variación Genética , Genética de Población , Virus de la Bronquitis Infecciosa/genética , Filogenia , Recombinación Genética/genética , Animales , Secuencia de Bases , Análisis por Conglomerados , Cartilla de ADN/genética , Genotipo , Virus de la Bronquitis Infecciosa/clasificación , Kazajstán , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Federación de Rusia , Alineación de Secuencia , Análisis de Secuencia de ADN , Especificidad de la Especie , UcraniaRESUMEN
An earlier study on commercial chickens and turkeys with a history of respiratory disease established Mycoplasma gallisepticum infection rates on 164 poultry farms of the Russian Federation. Forty-seven (29%) of these poultry farms were M. gallisepticum-positive by polymerase chain reaction but isolation of the mycoplasma was successful only on 10 farms. Five field isolates from different farms were selected for pathogenicity studies in specific pathogen-free chicks. Clinical signs, seroconversion, culture rates, air sac and tracheal lesions and mean tracheal mucosal thickness were all assessed in comparison with the reference strain, S6. Of the five isolates, MG140905 and MG070607 appeared to be slightly more pathogenic than the other three, as indicated by clinical signs, culture-positive rates and lesions, but only isolate MG140905 differed statistically (P < 0.05) from them, thus proving to be the most pathogenic. However, none of the Russian field isolates was as pathogenic as the S6 strain by the parameters measured. Stress or other factors such as concurrent bacterial or viral infections may have served as exacerbating factors for the disease seen in the naturally affected flocks. Sequence analysis of the gapA and mgc2 genes showed that MG140905 clustered with M. gallisepticum R(low) and was more distant from the majority of the Russian isolates.