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

Abstract

Aim: Infectious coryza is caused by Avibacterium paragallinarum. 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 A. paragallinarum 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 A. paragallinarum serovar A), Group 2 (unvaccinated and challenged by A. paragallinarum serovar B), Group 3 (vaccinated and challenged by A. paragallinarum serovar A), and Group 4 (vaccinated and challenged by A. paragallinarum serovar B). Vaccination was done using the tetravalent vaccine in oil-emulsion adjuvant contained A. paragallinarum 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 A. paragallinarum serovars A-L2447 and B-L1710 approximately 6×10⁸ 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 A. paragallinarum 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 A. paragallinarum serovars A and B isolated from Indonesia.

Keywords: Avibacterium paragallinarum; challenge test; clinical signs; serological test; vaccine.

Figure-1

The observations of post-challenge clinical signs. (a) Control (no clinical signs); (b) mild nasal discharge; (c) moderate bilateral facial edema; (d) severe facial edema, conjunctivitis, and hemorrhage.

Figure-2

Graphic representation of the clinical signs obtained from vaccinated and unvaccinated chickens challenged with Avibacterium paragallinarum serovars A and B 14 days post-infection. Mild facial edema unilateral was found in Group 2, Group 3, and Group 4 compared to Group 1 (p<0.05). Group 2 showed severe bilateral facial edema compared to Group 1 (p<0.05) */#p<0.05.

Figure-3

Pathological features of the facial dermis 14 days after infection: (a) Facial dermis of vaccinated chicken groups (no clinical signs found); (b) facial dermis of unvaccinated chicken groups (edema and mucopurulent exudate can be found subcutaneously).

Figure-4

Pathological feature of infraorbital sinus 14^th days after infection: (a) Infraorbital sinus of the vaccinated chicken group did not found macroscopic lessons; (b) infraorbital sinus of the unvaccinated chicken group shown mucopurulent discharge.

Figure-5

Facial dermal histopathological features from a group of unvaccinated chickens: (a) Infiltration of inflammatory cells and dominant heterophils (blue arrow), and caseous necrosis of the dermis layer (black arrow); (b) infiltration of inflammatory cells and dominant heterophils in the perivascular area (black arrow) (H and E, 400×).

Figure-6

Histopathological features of an infraorbital sinus from unvaccinated chickens: (a) Proliferation of mucosal epithelium (blue arrow), hypertrophy of mucosal gland (red arrow), and infiltration of inflammatory cells and dominant heterophils in the submucosa (black arrow) (H and E, 200×); (b) infiltration of inflammatory cells and dominant heterophils in the lumen of the sinus (H and E, 200×); (c) infiltration of inflammatory cells and dominant heterophils in the lumen of the sinus (H and E, 400×); (d) perivasculitis in the submucosa of the salivary gland (H and E, 100×); (e) infiltration of inflammatory cells and dominant heterophils in the perivascular area (H and E, 400×).