Coccidiosis in Chickens: Obligate Relationship between Eimeria tenella and Certain Species of Cecal Microflora in the Pathogenesis of the Disease

Abstract

The role of the cecal bacterial flora in influencing the development of coccidiosis due to Eimeria tenella was studied by isolating the predominant bacterial species from the ceca of specific-pathogenfree (SPF) and conventional chickens showing typical cecal coccidiosis. These isolants were used, along with measured doses of E. tenella oocysts, to produce cecal coccidiosis in bacteria-free White Leghorn chickens. The indigenous bacterial flora of the ceca of conventionally raised White Leghorn chickens varied with chicken age. Enterococci predominated up to 1 week of age, whereas Lactobacillus sp. predominated in 4-to-5-week-old chickens. Bacteroides sp., Escherichia coli, Lactobacillus sp., and Streptococcus fecalis were isolated regularly from conventional chickens at 1, 2, 3, 4, and 5 weeks of age. Clostridium perfringens was infrequent in conventional chickens but frequent in SPF chickens. Infection of chickens with Eimeria tenella stimulated the growth of C. perfringens in both conventional and SPF birds. Also, large numbers of E. coli and Bacteroides sp., but low numbers of Lactobacillus, were seen in the ceca of infected chickens.