Avian Eimeria species: effect of prior or simultaneous inoculation of one species on cellular invasion by a second species in vivo and in vitro.

The effect of prior or simultaneous administration of Eimeria acervulina on cellular invasion by E. acervulina, E. tenella, or E. adenoeides was examined in vivo and/or in vitro. In chickens immunized with E. acervulina oocysts, invasion by sporozoites from a challenge inoculum of E. acervulina increased slightly over invasion in naive controls, and invasion by sporozoites of E. tenella and E. adenoeides increased by factors of 1.99 and 2.26, respectively, over that in controls. Conversely, simultaneous inoculation of E. acervulina along with E. tenella or E. adenoeides did not have a significant effect on invasion. Cultured baby hamster kidney cells that had been previously inoculated with E. acervulina sporozoites also supported significantly greater (by factors of 1.39 to 2.66) invasion by E. adenoeides sporozoites than did control cultures. The enhancement of invasion in vitro appeared to depend upon either the interval between the inoculation of cells with E. acervulina and E. adenoeides or the interval between the replating of the cells and their inoculation with E. adenoeides. There were no gross changes in the culture morphology between the E. acervulina-inoculated and noninoculated cultures. The data indicate that prior exposure to E. acervulina enhances invasion by other species of avian coccidia and, therefore, may exacerbate the infection produced by these species.