Experimental Histomoniasis in Gnotobiotic Turkeys. II. Effects of Some Cecal Bacteria on Pathogenesis

Abstract

Turkeys harboring single species of bacteria were infected with bacteriologically sterile heterakid eggs containing Histomonas meleagridis. No indication of histomonad infection was observed in birds harboring either Bacillus cereus or Lactobacillus fermenti. A single case of liver infection was noted in eight birds harboring Streptococcus faecalis. Both liver and cecal involvement were seen in four of eight animals harboring Escherichia intermedia, and in one animal there were cecal lesions without hepatic infection. A caseous exudate, typical of severe cecal infection in conventional hosts, was not seen in any of these birds. The possibility that other bacteria may be responsible for such involvement was explored in two subsequent experiments. With E. intermedia and B. cereus as introduced cecal flora, cecal involvement was enhanced, but a caseous core was found in the ceca of 1 of 11 birds. In hosts harboring E. intermedia and L. fermenti, however, cecal infection was similar in most respects to that noted in their conventional counterparts. Results of a previous study suggested that bacteria-free turkeys are refractory to infection with Histomonas meleagridis (Doll and Franker, 1963). Ova from Heterakis gallinae were used as a source of histomonad infection in this preliminary study. The bacteria-free host also appeared refractory to heterakid infection. These findings indicate possible parasite-bacterial interrelationships. To determine whether these interrelationships involved specific members of the host flora, attempts were made to infect turkeys harboring single species of bacteria. The flora selected were isolated from the ceca of healthy birds. The results of these initial experiments pr mpted the use of additional host types. These were turkeys harboring two species of the selected flora. This report describes our