Histomoniasis in gnotobiotic chickens and turkeys: Biological aspects of the role of bacteria in the etiology

Abstract

The bacterial requirements for producing infectious enterohepatitis in bacteria-free chickens were different from those for the disease in bacteria-free turkeys. When both Escherichia coli and Clostridium perfringens were introduced with Histomonas meleagridis, mild atypical cecal lesions were produced in 3 of 28 chickens while typical liver and cecal lesions were both present in all of 25 turkeys. When single species of bacterial agents were used, the rate of infection was less. More lesions were produced with C. perfringens than with E. coli. The cecal bacterial flora of conventional chickens, when introduced into bacteria-free chickens, fulfilled the requirement of H. meleagridis for induction of infectious enterohepatitis. Attempts to define the specific bacteria involved in the etiology of the disease in chickens from among 48 different bacterial isolates and Candida albicans were unsuccessful, although very mild disease was produced inconsistently with various combinations of strains of E. coli with Pseudomonas aeruginosa and Streptococcus faecalis or with C. perfringens. Eimeria adenoides, a cecal coccidium, survived when introduced with Histomonos-infected Heterakis eggs into bacteria-free turkeys and supported the growth of some histomonads but not Heterakis gallinarium larvae. Eimeria adenoides did not simulate the role of bacteria in producing infectious enterohepatitis. Disease was produced and Heterakis larvae did survive in conventional turkeys receiving E. adenoides and infected Heterakis eggs. The essential contributing factor of bacteria in the pathogenesis of infectious enterohepatitis was determined to be neither a favorable pH nor an oxidation-reduction potential value within the intestine of the host. The oxidation-reduction potential of bacteria-free cecal contents was strongly positive, that of the conventional chicken with its indigenous microflora was strongly negative, while the potential of the contents of ceca with infectious enterohepatitis was intermediate. The pH of the bacteria-free cecum closely approximates that of the parasite-infected intestine, while the pH of the uninfected conventional cecum was somewhat lower. In the pathogenesis of infectious enterohepatitis, the role of bacteria apparently was more vital for the survival of Heterakis than Histomonas.