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Determination and analysis of Newcastle Disease Virus shed in chickens

Blair Telg, Jaime Thurk, John El-Attrache

Department of Veterinary Pathobiology, Texas A&M University


Trachea and fecal viral shed was evaluated via quantitative real-time RT-PCR for Newcastle Disease (ND) challenged birds with varying post-vaccination times as well as for ND challenged birds that received a varying number of vaccinations. All birds were challenged with a La Sota strain of Newcastle Disease Virus (NDV) at 109.2 EID50/ml. Trachea, fecal, and blood samples were collected three days post-challenge from all birds.  RNA was extracted and quantitative real-time RT-PCR was then performed to allow for the quantification of NDV viral RNA concentration per sample from each challenged bird.  Serological analysis of the NDV challenged birds with varying post vaccination times revealed undetectable levels of antibodies to NDV in all but two 1-week of age birds.  NDV viral RNA was detected in 20/25 (80%) of the tracheal swab samples indicating the presence of challenge virus replication.  However, only 3/25 (12%) of the fecal samples had detectable levels of NDV viral RNA.  No significant differences were observed in viral RNA concentrations between the groups with varying post-vaccination times.   For the birds with varying number of vaccinations, all vaccinated birds exhibited the presence of NDV antibodies while all non-vaccinated birds were negative for the presence of NDV antibodies.  As a result, only the non-vaccinated positive challenge control birds had detectable levels of NDV in trachea and fecal samples, indicating the presence of NDV challenge virus replication by quantitative real-time RT-PCR in all vaccinated birds, and the absence of replication in all unvaccinated birds.