Newcastle disease virus surveillance in Argentina: Use of reverse transcription-polymerase chain reaction and sequencing for molecular typification

Newcastle disease virus (NDV) remains a major pathogen of poultry where hig hly virulent strains require reporting to the Office of International Epizo otes. NDV is a paramyxovirus existing as different strains classified on th e basis of severity of the disease they cause. The present study was conduc ted in Argentina to determine the prevalence of highly virulent velogenic N DV strains in commercial poultry farms. Tracheal and cloacal swabs from 693 flocks, representing 14% of the broiler production, were collected and poo led. A pool amplified twice in embryonated eggs presented a limited hemaggl utination titer. We performed reverse transcription coupled to polymerase c hain reaction to amplify fusion and matrix protein gene sequences of the is olate and the strain Trenque Lauquen, isolated in Argentina during an outbr eak in 1970-71 and previously characterized as velogenic viscerotropic by b iological methods. The amino acid sequences were deduced From nucleotide se quences of the amplification products and the pathotype predicted according to the sequences obtained. From the samples analyzed, we found only one ty pe of NDV, being the isolate identified as lentogenic NDV. This strain is p robably the one used in vaccination of flocks where that sample was obtaine d. These data have allowed us to consider a velogenic NDV-free status in Ar gentina's commercia poultry