Susceptibility of vaccinated and unvaccinated Egyptian chickens to very virulent infectious bursal disease virus

Abstract

The responses of vaccinated and unvaccinated chickens of different breeds to infection with very virulent infectious bursal disease virus (vvIBDV) were investigated. Five-week-old chickens of five Egyptian breeds (Fayoumi, Balady, Golden, Mandarah, and Gimmizah), and foreign White Leghorn pullets were tested. In unvaccinated birds, mortality, relative bursa and spleen weight, bursal lesion score, antibody titres and the response of blood lymphocytes to mitogens were examined. The Gimmizah and Fayoumi birds showed the greatest susceptibility to infection with mortalities of 85 and 47%, respectively.

Reversion of molecularly engineered, partially attenuated, very virulent infectious bursal disease virus during infection of commercial chickens

“…These strains can cause lesions typical of IBDV and are antigenically similar to the classical strains (Eterradossi et al, 1992). Remarkably, however, vvIBDV can establish infection in the face of maternally derived antibodies as well as antibody levels after vaccination that were previously protective against classical strains (Hassan et al, 2002). Meanwhile vvIBDV infections also have been observed in Africa, Asia (for example, Eterradossi et al, 1999;Zierenberg et al, , 2001Parede et al, 2003;van den Berg et al, 2004) and in South America (Ikuta et al, 2001), but not in Australia (Sapats & Ignjatovic, 2002).…”

Extensive antigenic changes in an atypical isolate of very virulent infectious bursal disease virus and experimental clinical control of this virus with an antigenically classical live vaccine

“…The 99323 isolate was identified from Egypt during a worldwide survey of antigenic variation among IBDV strains causing acute IBD outbreaks. Such outbreaks have been reported to be a cause for continuing problems in the field in Egypt since the early 1990s, in spite of extensive and multiple administrations of live vaccines with various degrees of attenuation (Hassan et al, 2002). The 28% mortality induced by isolate 99323 following an experimental 10 4.24 EID 50 challenge in SPF chickens (not significantly different from that induced by strain 89163), the presence in the VP2 protein of 99323 of the four aa found in the typical vvIBDV, and the genetic relatedness between the nt sequences of 99323 and of typical vvIBDVs (as demonstrated by high bootstrap values in the consensus trees) all corroborate the fact that isolate 99323 is indeed a vvIBDV.…”

Egg:embryo weight ratio as an indicator of dwarfism induced by infectious bronchitis virus

“…Similarly spleen:body weight ratios are also used to assess spleenic atrophy (Hassan et al, 2002). The term bursal index is used to indicate the ratio obtained by dividing the BB ratio of infected/ vaccinated chickens by the BB ratio of uninfected/ unvaccinated chickens.…”