Epidemiological study of Newcastle disease in backyard poultry and wild bird populations in Switzerland.

Blood samples and cloacal swabs from poultry were collected in 107 small chicken flocks and 62 pure-bred poultry flocks to determine their status regarding Newcastle disease virus (NDV) infection. A questionnaire emphasizing potential contacts of poultry with wild birds and management practices associated with NDV infection was completed for each flock. Additionally, 1576 wild bird carcasses of 115 different bird species were collected from hunters and taxidermists. Poultry sera and tissue fluids of wild birds were tested for NDV antibodies using a blocking ELISA. Cloacal swabs were subjected to reverse transcription polymerase chain reaction (RT-PCR) for NDV genome detection. In-herd NDV seroprevalences between 5 and 29% were found in one small chicken flock, as well as in four pure-bred poultry flocks. NDV antibody positive wild birds were found in 10.2% of all wild birds examined. Highest proportions (i.e. 15%) of positive birds per species were found among sparrowhawks, kites, tawny owls, eagle owls, barn owls, cuckoos, swifts, cormorants and grebes. No NDV genome was detected in cloacal swabs. This study suggests that buying eggs or poultry abroad and exchanging poultry within the country were factors, more important than wild birds, to explain the higher NDV seropositivity in pure-bred poultry flocks.