Detección y caracterización molecular de cepas variantes del virus de la enfermedad infecciosa de la bolsa en el Estado Zulia, Venezuela

Abstract

Classical infectious bursa disease virus (IBDV) has been present in the Venezuelan poultry industry since the last quarter of the past century despite intensive vaccination programs applied to control the disease. Lately, the presence of variant strains has been reported in several Latin-American countries. This work reports the molecular identification of variant IBDV strains in poultry farms from Venezuela. Bursal imprints in Whatman classic indicator FTA® cards and bursa tissues for histopathological analysis were collected from 4-week old broiler flocks. Reverse transcriptase polymerase chain reaction (RT-PCR) and direct nucleotide sequence were used for the virus molecular characterization. The bird's body weight, the bursal index, the bursa weight and diameter were used to assess the immune status at four weeks of age. All the birds sampled (n =113) were IBDV positive. Viruses from 10 out of 13 farms showed high similarity with the IBDV variant strains (variants A and E). Histopathological findings where consistent with the RT-PCR, results showing IBDV related bursa damage in the infected birds. The immune status indicators were significantly affected in the farms where variant strains were detected. No variant strain live vaccination is currently used in Venezuela, increasing the risk of immunossupression, vaccine failure and susceptibility to endemic diseases.