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The Thai Journal of Veterinary Medicine

Abstract

Indirect enzyme-linked immunosorbent assay (I-ELISA) for antibody detection against A. paragallinarum serovars A, B and C was developed in separated plates. One hundred Babcock 308 female layer chickens were randomly divided into five groups of 20 each. Groups 1, 2, 3 and 4 were different positive control groups of immunized chickens with commercial trivalent mineral oil vaccine, and prepared bacterins of Avibacterium paragallinarum serovars A (221), B (0222) and C (Modesto), respectively. The chickens in Group 5 were assigned as a negative control. Positive and negative control sera from the chickens in Groups 1-5 at 2 weeks after the second vaccination were used to calculate sensitivity and specificity of the newly developed I-ELISA. Forty negative control sera (taken before vaccination) were used to evaluate cut-off values of the I-ELISA against each serovar of A. paragallinarum under optimal conditions. The cut-off values of serovars A, B and C, calculated by the mean optical density of all negative sera plus three standard deviations, were 0.334, 0.484 and 0.678, respectively. Efficacy of the developed I-ELISA showed 100% sensitivity for all three serovars of coating antigen, but with low specificity of 30% for all three serovars because of high cross-reactivity among the serovars, while the agreement rate between the I-ELISA and HI assay for serovars A, B and C was around 60%. Nevertheless, the serovar A I-ELISA gave a higher response to serovar A antiserum than to the other two heterologous serovars (p < 0.05). In contrast, the I-ELISA results for B and C did not show any significant differences between the homologous and heterologous serovars. This newly developed I-ELISA could be an alternative method for differentiating between A. paragallinarum-free chickens and those that have received vaccination, but could not clearly differentiate antibodies among the three serovars of A. paragallinarum.

Publisher

Faculty of Veterinary Science, Chulalongkorn University

First Page

241

Last Page

250

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