Comparison of Dynamics in Viremia Levels in Chickens Inoculated with M arek’s Disease Virus Strains of Different Pathotypes

Abstract：One day-old unvaccinated chicks were inoculated with serotype I virulent strain GA and vac— cine strain CVI988．semtype III vaccine strain HVT of Marek’s disease viruses(MDV)．By using an indirect immunofluorescence assay of suspensions of peripheral blood mononuclear 0e11s(PBMC)with monoclonal antibodies(MAb)BA4 and B specific to glycoprotein B of MDV，The dynamic courses of viremia levels for each of 3 strains from 4 days to 45 days postinfection(PI)were determind．Viremia f0r virulent strain GA—infected chiekens were detected from 4 days PI untiI days before death of infect— ed chickens．it got its peak at about 14 days PI．Viremm in serotype 1 vaccine CVI988一inoculated chickensweremeasured between 4t022 days PI．it couldbe detectedfrom 4 days PIan d ended at18 days PI，it got its peak at 8 days PI．For serotype 3 vaccine HVT-inoculated chickens，viremia could be detected beween 4 to 14 days PI，its peak happened at about 6 days PI．Such IFA with MAbs BA4 and B could be used r。evaluate quality of vaccination process in chicken flocks．Tbe differentiM dy— namie courses of viremia for different strains may be used t0 diagnose virulent V infection in vacci— hated flocks．The viremia levels measured by IFA with the MAbs an d co-cultivation assay for plague forming unit(PFU)were compared．The results indicated that IFA assay of PBMC suspension was more sensitive and specific than co—cultivation assay．i．e．viremia levels measured by IFA were 30 t0 100一fold bigher than that by plague—form ing assay in CEF for the same sampie