The avian pneumovirus (APV) outbreak in the United States is concentrated in the north-central region, particularly in Minnesota, where more outbreaks in commercial turkeys occur in the spring (April to May) and autumn (October to December). Comparison of the nucleotide and amino acid sequences of nucleoprotein (N), phosphoprotein (P), matrix (M), fusion (F), and second matrix (M2) genes of 15 U.S. APV strains isolated between 1996 and 1999 revealed between 89 and 94% nucleotide sequence identity and 81 to 95% amino acid sequence identity. In contrast, genes from U.S. viruses had 41 to 77% nucleotide sequence identity and 52 to 78% predicted amino acid sequence identity with European subgroup A or B viruses, confirming that U.S. viruses belonged to a separate subgroup. Of the five proteins analyzed in U.S. viruses, P was the most variable (81% amino acid sequence identity) and N was the most conserved (95% amino acid sequence identity).
Phylogenetic comparison of subgroups A, B, and C viruses indicated that A and B viruses were more closely related to each other than either A or B viruses were to C viruses.The Turkey rhinotracheitis virus, commonly referred to as avian pneumovirus (APV), is a member of the Paramyxoviridae family that causes acute rhinotracheitis in turkeys that is characterized by coughing, nasal discharge, tracheal rales, foamy conjunctivitis, and sinusitis in turkeys of all ages. In laying birds, there is a transient drop in egg production, along with mild respiratory tract illness (11). Uncomplicated cases have low mortality (2 to 5%), but APV infections accompanied by secondary infections (bacterial and/or viral) can result in up to 25% mortality (11). APV was first detected in South Africa in 1978 but was isolated soon thereafter in the United Kingdom,