RHDV and RHDVa replication, excretion and tissue distribution in rabbit kittens. Shown are virus genome copy numbers per μl whole blood (A, B) or rectal swab (C, D) as measured via RT-qPCR in samples from RHDV (A, C) and RHDVa (B, D) infected kittens 4–5 weeks of age at the indicated time points. SDL indicates the genome concentration relative to 20 genome copies detected in the RT-qPCR, which is considered the safe detection limit. E: Virus loads in tissues of RHDV and RHDVa infected kittens, 5 dpi. The safe detection limit of our assay in these tissues was 400 genome copies/mg on average (range 140–678 depending on the amount of tissue used for RNA extraction) or 20 genome copies/μl bile.