Intestinal interactions of Eimeria spp. with Clostridium perfringens and Salmonella Typhimurium in broiler chickens

Abstract

Coccidia, Clostridium perfringens, and Salmonella are intestinal pathogens in broiler production. Coccidiosis in chickens is caused by Eimeria spp. The infection provides a growth advantage to Clostridium perfringens (CP), sometimes leading to necrotic enteritis. Salmonella has a high zoonotic potential and coccidiosis is responsible for large economic losses in the broiler industry. Prevention strategies in broiler production include vaccination programs and approaches to improve the bacterial composition in the intestines to alleviate the negative impacts of the diseases. In chapter 2 of this thesis, the data of 17 studies about intestinal microbiota after infection with coccidia and/or CP were synthesized in a meta-analysis. Meta-analyses of three different data sets were performed: on data of nine experiments on chickens infected with coccidia only; on data of four studies on chickens infected with CP only; on raw data of eight experiments with chickens infected with coccidia and CP. No significant differences in the relative abundance of bacterial families were found. The analyses of functional profiles showed a more uniform reaction to the infections with the relative abundance of many pathways significantly altered. Alpha diversity was not affected by infection with either pathogen or the combination. In conclusion, the heterogeneity of these microbiota studies makes recognizing common trends difficult, although it seems that coccidia infection affects the microbiota more than an infection with CP. The aim of the studies presented in chapters 3 and 4 was to investigate the interaction of Salmonella Typhimurium (ST) and coccidiosis vaccinations on the intestinal health of broiler chickens. The experimental design considered groups vaccinated against coccidiosis and against ST on day 14. On day 28, all groups were challenged with a ST marker strain. Samples were collected on day 28, 35, and 42. The results of the re-isolation of the ST marker strain from the environment, the cecal content and liver tissue confirmed the efficacy of the ST vaccine on the day of hatch, followed by a booster vaccine on day 14. On day 42 cecal IgA and IgG showed differences in groups vaccinated against coccidiosis compared to ST vaccinated groups. The analysis of the cecal microbiota showed differences in the diversity and in the abundance of functional pathways on days 28, 35 and 42 between groups vaccinated against coccidiosis compared with groups not vaccinated against coccidiosis or only vaccinated once against ST. Gene expression of Claudin 1, Claudin 4, E cadherin B catenin and Zonula occludens 2 in the cecal wall differed between groups on days 28 and/or 42. The analysis of the transcriptome in the cecal wall revealed potential implications for cell-cell junction upregulation and intestinal epithelial integrity in response to the ST vaccine. Overall, the results indicated the potential influence of the coccidiosis vaccine, which becomes apparent after the ST challenge and the importance of the booster vaccine.