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UBC Theses and Dissertations

Strategy to develop alternative to antibiotics using bacterial second messenger 3’, 5’ cyclic diguanylic acid as an immunostimulator in broiler chicken Fatima, Mussarat


In this study the bacterial second messenger, 3’, 5’ cyclic diguanylic acid (c-di-GMP) was evaluated as a vaccine and therapeutic adjuvant in broiler. The humoral immune response to an oral infectious bursal disease virus (IBDV) vaccine administrated in conjunction with intramuscular injection (IM) or oral administration of 10 nmol or 100 nmol c-di-GMP in 192 broiler chickens. The antibody titers were determined in blood sera weekly in 8 birds /treatment. From d 14 to 35, an increase (P < 0.05) in the total immunoglobulin (IgA) titers was observed regardless of treatments. On d 35, birds receiving c-di-GMP by gavage showed higher serum IgA levels when compared the control birds (P < 0.05). To explore strategies to control Clostridium perfringens colonization in gut, the synergistic effect of c-di-GMP with penicillin G was investigated in a broiler challenge model. A mixture of C. perfringens type A strains from necrotic enteritis outbreaks were inoculated on d 14-16. Birds were treated with saline (control group) or 20 nmol of c-di-GMP by gavage or IM on d 24, all in conjunction with penicillin G (PG) in water for 5 d. Weekly samplings of ceca and ileum were performed on d 21 to 35 for C. perfringens and Lactobacillus enumeration. On d 35 of age, the IM treatment (P < 0.05) reduced C. perfringens in the ceca, suggesting possible synergistic activity between PG and c-di-GMP against C. perfringens in broiler ceca. The AFLP and the cpa gene prevalence results demonstrated that c-di-GMP per IM decreased the prevalence of cpa while restored the normal microflora on the day 35 after being challenged by high doses of C. perfringens. Thus c-di-GMP has a promise to improve poultry health by modulating mucosal immunity and reducing pathogens in the gut.

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