Avian metapneumovirus in the USA

Avian metapneumovirus (aMPV) causes a respiratory infection in turkeys and chickens of all ages. This virus, also known as turkey rhinotracheitis virus or TRT, is a member of the paramyxoviridae family of viruses. Although there are several subtypes of the virus, three subtypes, A, B and C, are most commonly associated with disease in poultry.

Various subtypes differ in their genetic makeup and cross-neutralization ability. Subtypes C is the only subtype detected in the U.S.A.; subtypes A and B are prevalent in other parts of the world, including Europe. In the U.S.A., aMPV causes an upper respiratory tract infection in turkeys; no outbreaks have been reported in commercial chicken flocks. In other parts of the world where subtypes A and B are endemic, both chickens and turkeys are affected. aMPV-induced disease in chickens is called “swollen head syndrome” because of grossly enlarged sinuses, possibly due to mixed infections with aMPV and other viral and bacterial agents.

Although outbreaks due to aMPV have been documented since 1970s, the virus was not identified in the U.S.A. until 1996. The first outbreak occurred in the state of Colorado. This outbreak was restricted to one large commercial turkey operation. With careful management, the virus was quickly eradicated from this operation. 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. Fortunately, the rate of spread has been slow and the virus has remained localized in the Midwestern region of the country. Turkey flocks in the endemic areas experience recurring losses due to immunosuppression caused by aMPV. These losses are tempered by the use of a live attenuated vaccine.

For current incidence and control measures in the USA, follow the links in the left menu.

This information is supplied by Dr. Jagdev M. Sharma.