Efficacy of tetravalent coryza vaccine against the challenge of serovars A and B isolates from Indonesia in chickens.

AIM

Infectious coryza is caused by . In Indonesia, this infection results in a 10%-40% decrease in egg production by laying hens. This study was conducted to determine the effectiveness of tetravalent coryza vaccine contained bacterin serovars A, B, C2, and C3; strain A-221, B-Spross, C2-Modesto, and C-3-Akko in layers based on antibody titer and clinical signs using a post-challenge test.

MATERIALS AND METHODS

Forty four-week-old Lohmanns strain chickens were used in this study. Forty chickens were divided into four groups for serological and challenge test: Group 1 (unvaccinated and challenged by serovar A), Group 2 (unvaccinated and challenged by serovar B), Group 3 (vaccinated and challenged by serovar A), and Group 4 (vaccinated and challenged by serovar B). Vaccination was done using the tetravalent vaccine in oil-emulsion adjuvant contained bacterin serovars A, B, C2, and C3; strain A-221, B-Spross, C2-Modesto, and C-3-Akko. Vaccination was performed at day 1 and booster was done at day 14. Blood serum was collected on days 0, 14, and 28 for the hemagglutination-hemagglutination inhibition (HI) test. The challenge test was given at day 29 through intranasal administration using serovars A-L2447 and B-L1710 approximately 6×10 CFU/mL. Clinical signs were observed for 14 days post-infection. At the end of the study, chickens were euthanized, and pathological features of the infraorbital sinus, facial skin, and trachea were recorded.

RESULTS

Data analysis of antibody titers and pathological changes was performed descriptively, while clinical symptom scores were analyzed non-parametrically with the Mann-Whitney U-test using SPSS version 21. At days 14 and 28 post-vaccination, the antibody titer in Group 3 was 5 HI and 20 HI, respectively. However, the antibody titers in Group 4 at 28 days post-vaccination were 0 HI. Clinical observations, the vaccinated groups that were challenged with serovars A and B showed clinical symptoms on days 4 and 6 post-infection, namely mild unilateral facial edema and severe bilateral facial edema, respectively. Clinical signs in Groups 3 and 4 were less severe than in Groups 1 and 2 (p<0.05). Pathological examination findings supported clinical observations and serological testing.

CONCLUSION

Tetravalent coryza vaccine in chickens has efficacy to protect against the challenge test of serovars A and B isolated from Indonesia.