“…However, the influence of vaccination and/or co-infection, for example with immunosuppressive agents such as circovirus (Todd, 2000), on the nature of pPMV-1 quasispecies is also worth studying. Indeed, such an influence has been shown for other viruses Essajee et al , 2002), and such a hypothesis relating to an interaction between the quasispecies nature of pPMV-1, vaccination and coinfections, together with the fact that suspect cases are more systematically reported, might explain why more and more cases of pigeon paramyxovirosis are recorded in Europe (Commission of the European Community, 2000; Terregino et al , 2003) despite the strengthening of control measures.…”