Routine monitoring of Marek's disease virus in poultry dust in Australia

Since 2004 a major Australian poultry company in has used routine monitoring for MDV serotype 1 (MDV1) in poultry dust using serotype-specific real-time quantitative PCR (qPCR) as part of their MD management strategy, particularly in one production region. Dust samples are collected from one house for each farm batch at approximately 6 weeks of age. Combined with standard PCR monitoring of in ovo HVT vaccination in spleen samples, the monitoring program allows assessment of broiler vaccination value, assessment of the seasonal pattern of MDV1 presence and evaluation of MDV1 challenge levels over time. In the one region monitored consistently over the period MDV levels in dust have fallen to very low levels in the last two years. Monitoring has also allowed a rapid comparison of MDV1 status in new sections of the operation. Between 2005 and 2011 1487 shed dust samples were analysed for MDV1 by qPCR with 22.5% being positive for MDV overall. The positive rate ranged from a low of 6% in 2007 to 40% in 2010. Mean (±SD) MDV copy number per mg of dust in positive samples was 4.51±3.2 x 105 on the untransformed scale or 3.96±1.14 on the log10 transformed scale. The range in annual averages on the two scales was 0.091 to 13.2 x 105 with peak levels in 2009 reflecting samples from a new region with very high counts. The experience has been that routine monitoring of MDV by qPCR is a useful tool in managing cost effective control of MD in broiler operations.