Swollen Head Syndrome

Avian metapneumovirus (aMPV) causes turkey rhinotracheitis also known as avian pneumovirus infection of turkeys, which is an acute respiratory tract infection of turkeys. It is also associated with Swollen Head Syndrome also known as avian rhinotracheitis in broilers and broiler breeders, as well as with reproductive disorders that result in a marked drop in egg production in chickens and ducks.

The typical clinical signs seen in chickens infected with the virus include swelling of the periorbital and infraorbital sinuses, particularly around the eye, coupled with mild conjunctivitis. Some respiratory signs were also observed. The disease usually lasts from two to three weeks.

The Swollen Head Syndrome affects not only chickens, turkeys, and guinea fowl, but also pheasants, and Muscovy ducks. Furthermore, geese, most other duck species, and possibly pigeons are thought to be refractory to disease.

Respiratory signs occur in young birds and the adults are affected by drops in egg production, usually by from 5% to 30%. The transmission of the virus is lateral by aerosol through the respiratory route. It is spread by both airborne and mechanical (feed, water, and equipment) routes.

Avian metapneumovirus was first detected in turkeys in South Africa in the late 1970s, and has since spread to all major poultry-producing regions of the world, except Australia.

In 2001, the first human metapneumovirus (hMPV) was isolated in The Netherlands and classified as a member of the genus Metapneumovirus, which predominantly causes respiratory infections in humans.

Experimental studies suggest that turkeys also are susceptible to hMPV[1]. Complete genome sequencing has confirmed that the genomic organization of hMPV is similar to that of aMPV.

Vaccines are available for immunization of chickens and turkeys, and they are widely used in countries where the disease is endemic.

[1] Velayudhan et al: Human metapneumovirus in turkey poults in Emerging Infectious Diseases – 2006