MATERIALS AND METHODS

Examination of domestic turkeys and wild birds. In 2002, nasal turbinate tissues or swabs (Becton Dickinson, Sparks, MD) and serum samples were collected from most commercial turkey farms in North Dakota and South Dakota. Turbinate tissues or swabs from each flock (n= 10) were pooled into 1.5 ml of collection medium containing minimal essential medium (Invitrogen Corporation, Grand Island, NY), 200 units/ml penicillin G sodium, 200 μg/ml streptomycin sulfate, 0.75 μg/ml amphotericin B, and 150 μg/ml gentamicin. The samples were centrifuged at 800 3 g for 10 min and analyzed for APV RNA by 59-nuclease reverse transcriptase–polymerase chain reaction (59-nuclease RT-PCR). In addition, serum samples were collected from commercial turkey flocks in Manitoba (Canada), North Dakota, South Dakota, Minnesota, Iowa, and Wisconsin and tested for APV-specific antibodies by enzyme-linked immunosorbent assay (ELISA). For wild birds, choanal cleft swabs or nasal turbinates were collected from common terns (Sterna hirumdo), ring-billed gulls (Larus delawarensis), house or English sparrows (Passer domesticus), and snow geese (Chen caerulescens) and processed as described above to detect APV.