Serologic Status of Newcastle Disease in Native Chickens by Hemagglutination Inhibition Test
Newcastle disease (NCD) is a poultry disease caused by avian Paramyxovirus type 1, characterized by gastrointestinal, respiratory and neurological symptoms. The study established the prevalence of NCD in native chickens and evaluated the protection levels of vaccinated chickens. Blood serum samples were subjected to hemagglutination inhibition test. A total of 75 blood samples were collected from five sites in Davao City: 60 samples from four unvaccinated native chicken farms, and 15 from a vaccinated broiler farm. Results showed seven (7) unvaccinated native chickens with positive titer levels ranging from 2 to 32, of which two(2) were considered significant, indicating protection even without an elicited immune response. This cannot be simply attributed to environmental factors considering uniform exposure of other individuals to similar conditions but exhibited no positive titers. The significant titer count of vaccinated samples ranging from 16 to 128 is attributed to their vaccination history. Differences in titer levels despite similar vaccine administration indicate a disparity in levels of protection due to different individual antibody immune responses, and efficacy of vaccines. Analysis by Chi-square goodness of fit test showed no difference in the titer levels of native chickens, which was expected as they did not have previous exposure to NCD and most had no titers. The two significant titer levels were considered outliers and provided a possible genetic perspective with pre-immune antibodies and natural resistance of native chickens as the focus. Gene analysis and isolation, as well as the prevalence of NCD in other localities, are recommended for future studies.
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