Evaluation of Humoral Immune Response in Dual-Purpose Hens Vaccinated Against Newcastle Disease in Vinto-Cochabamba

Abstract

Introduction: Newcastle disease is a highly contagious viral disease that affects and causes significant damage to domestic and wild birds. Vaccination is the best method for its control; however, this procedure is carried out differently in intensively farmed poultry compared to backyard family-raised birds. Using different vaccination protocols and techniques can either increase or decrease vaccine effectiveness; this study evaluates the efficiency of a vaccination protocol currently used to create projective antibody titrations against Newcastle disease in the locality of Vinto. Methodology: This experimental study evaluated the humoral immune response in a population of backyard dual-purpose hens provided by the autonomous municipal government of Vinto, vaccinated against Newcastle disease with a modified oral vaccination protocol by mixing the vaccine with food. A total of 66 individuals were randomly sampled with two repetitions, yielding 132 serological samples from birds, which were divided into two groups: prime-vaccinated and previously vaccinated. Additionally, serum samples were taken before vaccination and 4 weeks afterward. Antibody titers were determined using the ELISA assay and compared using ANOVA tests and Turkey post-hoc analysis. Results: This study conducted the first evaluation of post-vaccine antibodies against Newcastle in backyard birds in Bolivia. The results did not show a statistically significant increase in post-vaccine antibody titers in the groups compared to pre-vaccination antibody titers; moreover, there was high variability or non-uniformity in response, showing deficiencies regarding the efficiency of the vaccination protocol. Discussion: Contrary to previous studies, vaccination did not induce an adequate antibody response and presented great variability in conferring humoral protection against Newcastle disease in backyard laying hens, creating a risk of immunized population pockets. Coordinated interventions among producers, industry, and government are required to improve vaccination programs in family poultry farming and to effectively control this devastating avian disease.