Submitted to: Animal Health Research Reviews
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 27, 2000
Publication Date: September 15, 2000
Interpretive Summary: Avian pneumoviruses cause disease in turkeys referred to as turkey rhinotracheitis (TRT). These agents may also cause a swollen head syndrome (SHS) in chickens. The virus was first isolated in South Africa during the 1970's and was then discovered in Europe, Asia and South America. These virus types were previously not found in North America. However, during 1996 an outbreak of TRT emerged among turkeys in the United States and the virus isolation was officially reported during 1997. The virus in the United States was distinct from European viruses based on antibody detection methods and was difficult to propagate using standard culture systems. Studies of the genetics of these viruses has resulted in the United States virus being designated a new type of avian pneumovirus.
Technical Abstract: Avian pneumovirus (APV) primarily causes an upper respiratory disease recognized as turkey rhinotracheitis (TRT) or swollen head syndrome (SHS) in chickens. The virus was first isolated in South Africa during the early 1970's and has subsequently been reported in Europe, Asia and South America. As of February, 1997 a serologically distinct APV isolate was officially reported in the U.S. following an outbreak of TRT during the previous year. This was the first report of these virus types in the U.S. that were previously considered exotic to the U.S. and Canada. Predicted matrix (M) proteins of European APV type A and B isolates share 89% identity in their amino acid sequence. However, the predicted M protein of APV/CO was only 78% similar to APV type A and 77% similar to APV type B protein sequences. The predicted amino acid sequence of the U.S. APV isolate's fusion (F) protein had 72% sequence identity to the F protein of APV type A and 71% sequence identity to the F protein of type B. This compares with 83% sequence identity between the APV type A and B predicted amino acid sequences of the F protein. Lack of sequence heterogeneity among U.S. APV isolates over two years suggests these viruses have maintained a relatively stable population since the first outbreak of TRT. Phylogenetic analysis of the M and F proteins, along with the serological uniqueness among APV isolates supports classification of U.S. isolates as a new APV type C.