Molecular characterization of infectious bursal disease virus from broiler flocks in Lusaka, Zambia

This study was aimed at determining the strains of infectious bursal disease virus (IBDV) present in Zambia causing disease in vaccinated broiler flocks. Despite routine vaccinations with appropriate IBDV vaccines, which is a control strategy of infectious bursal disease (IBD), many poultry farms still experience high mortalities to the disease (PAZ, 2013).

A molecular study on IBDV isolated from Lusaka District was performed based on partial sequences of segments A (VP2) and segment B (VP1) of the viral genome from IBD outbreaks from 20 broiler farms. In total, 16 and 11 partial nucleotide sequences of VP2 and VP1 were determined, respectively. Evolutionary analysis of both VP1 and VP2 showed that most Zambian isolates belonged to the African very virulent IBDV (VVIBDV) group which includes isolates from Nigeria, Tanzania and South Africa (Kasanga et al., 2013). In contrast, it was interesting to note that one isolated strain (LUSC11-12) was genetically identical to an attenuated vaccine strain (MB) and showed 100% nucleotide sequence identity to the strain in both the VP2 and the VP1. The current study does not only demonstrate the predominance of African-like VVIBDV, but also documents for the first time the possible involvement of attenuated vaccine strains in the evolution and epidemiology of IBD in Zambia.

From the above study findings, several recommendations were made which included ;further studies, surveillance and characterization of IBDV in poultry; monitoring of live vaccine use in the field, Development of a vaccine from local or regional IBDV field strains and Strict biosecurity of poultry farms