Submitted to: Review Article
Publication Type: Review Article
Publication Acceptance Date: 11/1/2012
Publication Date: 11/2/2012
Citation: Yu, Q. 2012. Avian metapneumovirus in the USA. Review Article. 2012 CDROM.
Interpretive Summary: The United States of America (USA) was considered free of Avian metapneumovirus (aMPV) until the first outbreak occurred in the state of Colorado. A few months later, the virus appeared in Minnesota. Since its first detection in 1997, aMPV has become endemic in Minnesota and the surrounding states. A number of aMPV isolations were made from the turkeys and wild birds in the endemic area. Molecular analysis of these viruses has shown that the USA isolates of aMPV are genetically and antigenically different from their counterparts, aMPV-A and aMPV-B, which circulated Europe and other parts of the world. Thus, the USA isolates are classified into a new subgroup C (aMPV-C). To prevent the disease caused by aMPV-C infections, a live, attenuated vaccine has been developed and used in the endemic area. Fortunately, since the use of the live attenuated vaccine plus the practice of restricted biosecurity measurement in the endemic area, the incidence of aMPV-C outbreaks has declined. At the present time, there are no reports of aMPV-C outbreaks in commercial turkeys in the USA. However, serologic surveillance shows an occasional positive for aMPV-C antibody in turkey breeders in Minnesota and the neighboring states.
Technical Abstract: In the United States of America (USA), avian metapneumovirus (aMPV) causes an upper respiratory tract infection in turkeys; no outbreaks have been reported in commercial chicken flocks. Typical clinical signs of the disease in turkey poults include coughing, sneezing, nasal discharge, tracheal rales, foamy conjunctivitis and swollen infraorbital sinuses. The virus also causes a rapid drop in egg production in breeding and layer turkeys. The disease is usually accompanied by secondary bacterial infection that can increase morbidity and mortality, resulting in significant economic losses to the turkey industry.