Development and evaluation of sustainable methods for enteric protozoal and bacterial disease prevention in poultry

The following studies evaluated a recombinant vectored vaccine against coccidiosis in broilers, followed by the development and testing of potential Bacillus-based spore probiotics for Salmonella control in poultry. Finally, a reproducible model for Necrotic Enteritis was developed in controlled laboratory challenge studies. A Salmonella-vectored recombinant coccidiosis vaccine was administered to day-old chickens and protection upon Eimeria challenge was analyzed by measuring performance, mortality, lesion scores, and antibody titers elicited by the vaccine candidate. Beneficial effects on performance and reduced mortality (p< 0.05) were observed in vaccinated chickens. The ill-effects of Salmonella as a food-borne pathogen are well-documented, and the next set of experiments involved the selection and testing of several candidate Bacillus isolates as potential spore based probiotics, with evidence that this could lead to an effective preventative for Salmonella control in poultry. From an initial screen, one isolate PHL- NP122 was most significant in reducing (p< 0.05) Salmonella in both broilers and turkeys in addition to enhancing performance. In the final study, the ability of a Salmonella infection at hatch to alter the ability of broilers to secondary bacterial infections was investigated. In Chapter 5, a unique laboratory challenge model for Necrotic Enteritis was developed which involved a paratyphoid Salmonella infection as a predisposing factor for development of this disease. In broilers that were challenged with Salmonella at hatch, there was increased mortality and lesion scores (p< 0.05) associated with Necrotic Enteritis than the control group that did not receive any Salmonella. Additionally, a significant reduction (p< 0.05) in performance was observed when the disease was induced by a Salmonella challenge. These findings may have direct consequences for commercial production since Salmonella control may be important for prevention of Necrotic Enteritis, a major disease of poultry worldwide.