Protection Provided by Rispens CVI988 Vaccine Against Marek's Disease Virus Isolates of Different Pathotype and Early Prediction of Vaccine Take and MD Outcome.

Protection Provided by Rispens CVI988 Vaccine Against Marek's Disease Virus Isolates of Different Pathotype and Early Prediction of Vaccine Take and MD Outcome.
Avian Pathol. 2015 Oct 27;:1-31
Authors: Ralapanawe S, Walkden-Brown SW, Renz KG, Islam AF
Abstract
We tested the level of protection provided by the Rispens CVI988 (Rispens) vaccine against challenge with a virulent Marek's disease virus (MDV) pathotype (vMDV) and a very virulent pathotype (vvMDV) and the accuracy of a range of predictive measures of MD incidence and vaccine take. Commercial ISA Brown layer chicks (n=236) were vaccinated (or not) with 4000 pfu of Rispens vaccine at hatch and challenged (or not) with 500 pfu of each challenge virus five days post vaccination. The vvMDV pathotype FT158 induced higher MD incidence (65%) and mortality (33%) when compared with the vMDV pathotype MPF57 (39% and 8% respectively). The protective index (PI) provided by the Rispens vaccine against FT158 (61%) did not differ significantly from that against MPF57 (66%). This provides additional evidence that protection provided by the Rispens vaccine is not influenced by pathotype determined in studies using vaccines of other Mardivirus species. The challenge viruses did not differ in MDV or Rispens viral load in spleen at 14 dpc determined by specific qPCR. MDV load in peripheral blood leucocytes (PBL) at 7 and 14 dpc, splenocytes at 14 dpc, feather cells at 14 and 21 dpc and isolator ...

Source: Avian Pathology - October 27, 2015 Category: Pathology Authors: Ralapanawe S, Walkden-Brown SW, Renz KG, Islam AF Tags: Avian Pathol Source Type: research