Abstract
BackgroundAvian metapneumovirus subtype C (aMPV/C) causes severe upper respiratory disease in turkeys. Previous report revealed the presence of aMPV/C in wild birds in the southeast regions of the U.S.MethodsIn this study, aMPV/C positive oral swabs from American coots (AC) and Canada geese (CG) were passaged three times in the respiratory tract of specific pathogen free (SPF) turkeys and used as aMPV/C P3 virus isolates in subsequent studies.ResultsWild bird P3 isolates showed similar growth characteristics when compared to virulent aMPV/C in chicken embryo fibroblast ( CEF) cell cultures and their glycoprotein G gene sequence was closely related to the G gene of aMPV/C Colorado reference virus. Three-day-old commercial or SPF turkeys were inoculated oculonasally with wild bird aMPV/C P3 isolates. At 5 and 7 days post-inoculation (DPI), severe clinical signs were observed in both of the AC and CG virus-exposed groups. Viral RNA was detected in tracheal swabs by reverse transcriptase polymerase chain reaction (RT-PCR). In addition, immunohistochemistry showed virus replication in the nasal turbinate and trachea. All virus-exposed turkeys developed positive antibody response by 14 DPI.ConclusionsOur data demonstrate that aMPV/C wild bird isolates induced typical aMPV/C disease in the domestic turkeys.
Highlights
Avian metapneumovirus subtype C causes severe upper respiratory disease in turkeys
Identified in South Africa in the late 1970s [5], Avian metapneumovirus (aMPV) later spread to Europe, Asia, and South America [4,6,7,8,9,10,11]. Avian metapneumovirus subtype C (aMPV/C) was first isolated in the United States during 1996 in Colorado [12,13] and subsequently outbreaks were reported in Minnesota [14] where the disease has emerged as a major economic problem for the turkey industry
The positive swabs were pooled and subsequently passaged three times in the upper respiratory tract of specific pathogen free (SPF) turkeys, turbinate and tracheal samples were processed as described in materials and methods
Summary
Avian metapneumovirus subtype C (aMPV/C) causes severe upper respiratory disease in turkeys. AMPV/C was first isolated in the United States during 1996 in Colorado [12,13] and subsequently outbreaks were reported in Minnesota [14] where the disease has emerged as a major economic problem for the turkey industry. The aMPV isolates that exist worldwide are currently classified into four subtypes, namely, subtypes A, B, C, and D. The US isolates belong to subtype C [23,24], while the majority of aMPVs isolated in Europe, Asia, and South America belong to the subtype A or B [6,25,26]. In 2000, it was reported that aMPVs isolated in France in 1985 belong to subtype D [25]
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