3.2 Virological results
All animals tested negative to RHDV and RHDV2. The male rabbit, with two years old, was seropositive with high antibody titter (RI10 = 18.4). No serum was available from the five dead rabbits due to blood coagulation. The owner reported no previous vaccination, but being the oldest animal in the group, we cannot exclude that it may have contacted with classic MYXV strains in the past, acquiring some level of cross-immunity, allowing its survival.
The Cq values obtained with the qPCR-MYXV targeting the diploid gene M0005L/R in the tissues from three rabbits revealed high viral charges in a pool of liver and spleen ( 1.49E+07 to 4.48E+09 copies/mg ), lungs ( 6.44E+07 to 4.44E+09 copies/mg ), eyelid ( 2.45E+10 to 8.45E+10 copies/mg) and genitalia ( 1.51E+09 to 2.48E+09 copies/mg ).
The amplicon size obtained with the 9E/9F system (≈ 3100), confirmed that rabbits were infected with the recombinant MYXV and not with classic MYXV strains. Further nucleotide sequencing of an 859nt fragment from two rabbits (MT920563 and MT920564) revealed 100% of similarity between the two sequences. BLAST analysis showed also 100% of identity with the homologous region encompassing M061L and M064L of sequence MK340973 (ha-MYXV), confirming that rabbits were infected by the MYXV recombinant myxoma virus.