Characterization of Mexican Strains of Avian Infectious Bronchitis Isolated during 1997

Abstract

Ten infectious bronchitis virus (IBV) isolates were recovered from broiler chickens in the states of Queretaro and Guanajuato in Mexico. The viruses were isolated from trachea, lung, kidney, and cecal tonsils of birds that showed respiratory signs in spite of vaccination with Massachusetts (Mass) and Connecticut strains of IBV. Each isolate was identified by an accession number from 1 to 10. Six of the isolates were neutralized by Mass monoclonal antibodies, whereas the other four were not. In addition, these four isolates did not produce lesions in embryos in the first five to seven passes. These four isolates were further characterized by the reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism techniques. The electrophoretic patterns for the four isolates were identical but were different from other known IBV isolates.

Gastric gross and microscopic lesions caused by the UNAM-97 variant strain of infectious bronchitis virus after the eighth passage in specific pathogen-free chicken embryos

“…Electron microscopy showed only viral particles with morphology consistent with coronaviruses. The molecular reverse-transcriptase-PCR-RFLP pattern of the S1 protein gene was unique for the UNAM-97 IBV variant strain, which differed greatly from those of other strains prevalent in Mexico (Escorcia et al, 2000). This new variant strain was isolated from 5-to 7-wk-old broilers previously vaccinated with Massachusetts and Connecticut IBV strains.…”

“…Despite the use of these IBV vaccines, it is common to find IB problems in immunized chickens, causing a large economic impact. We have previously reported that IBV obtained from trachea, lung, kidney, and cecal tonsil of broiler chickens, and further characterized using the reverse transcriptase PCR and RFLP techniques, showed electrophoretic patterns different from other known IBV isolates (Escorcia et al, 2000).…”

“…This new variant was named UNAM-97, which together with strain BL-56, is now officially recognized as one of the two variant strains in Mexico (Escorcia et al, 1998;Lozano et al, 1998;Del Río et al, 1999;Escorcia, 1999;Petrone et al, 1999;Camacho et al, 2000;García et al, 2001;Gay et al, 2000). The importance of these new variant strains is that for the first time there was an outbreak that could not be controlled by immunization with the Mass and Conn strains (Escorcia et al, 2000). Herein is described macroscopic and microscopic lesions found in specific pathogen-free chicken embryos experimentally caused by UNAM-97 IBV variant strain after the eighth passage, and the presence of the virus by electronic microscopy.…”

Infectious bronchitis virus variants: a review of the history, current situation and control measures

“…Elsewhere in Latin America a variant IBV was isolated from commercial chickens in Honduras in 1997 and poor protection against Mass vaccines was demonstrated (Cook et al, 1999). Following the isolation of the Ark serotype in Mexico in the early 1990s (Quiroz et al, 1993), the use of molecular methods subsequently identified IBV variants unique to that country in commercial chickens (Escorcia et al, 2000;Callison et al, 2001;Gelb et al, 2001). They were shown by neutralization tests to be different from Mass or Conn serotypes, but in vivo protection studies were not performed.…”

Viral agents related to enteric disease in commercial chicken flocks, with special reference to Latin America

“…Many of these strains have been related to respiratory diseases (Cubillos et al, 1991;Escorcia et al, 1997;Alvarado et al, 2005;Rimondi et al, 2009), but in Brazil, the strains have been related to enteric problems (Villarreal et al, 2007). Many of these strains have been related to respiratory diseases (Cubillos et al, 1991;Escorcia et al, 1997;Alvarado et al, 2005;Rimondi et al, 2009), but in Brazil, the strains have been related to enteric problems (Villarreal et al, 2007).…”