Course of induced infection by Eimeria krijgsmannni in immunocompetent and immunodeficient mice

Abstract

Recently, we have demonstrated the utility of Eimeria krijgsmanni as a novel mouse eimerian parasite for elucidating the biological diversity. The parasite showed notable infectivity to mice with various levels of immune status and susceptibility to antimicrobial agents including coccidiostat. However, the detailed lifecycle of E. krijgsmanni had not yet been determined and this information was lacking in discussion of previous findings. In the present study, we clarified the morphological characteristics of E. krijgsmanni and its lifecycle in normal mice, and examined the effects in immunodeficient mice and lifecycle stage for challenge infections after the primary inoculation. In immunocompetent mice, the lifecycle consisted of four asexual stages and the sexual sages followed by formation of oocysts during the prepatent periods. Interestingly, the second-generation meronts were detected in all observation periods after the disappearance of the other stages. For the challenge infection of immunodeficient mice, all developmental stages except for the second generation meronts were temporarily vanished. This finding suggests a "rest" or marked delay in development and a "restart" of the promotion toward the next generations. The second generation meronts may play an important role in the lifecycle of E. krijgsmanni.

Experimental evaluation of pathogenicity and acquired immunity of Eimeria species, E. uekii and E. raichoi, infecting Japanese rock ptarmigans in a subspecies of the birds

“…The development of Eimeria spp. zoites in primary immunized mice was shown to stop at the second of 4 asexual generation stages among a total of 5 stages (4 asexual and 1 sexual) after challenge ( Ono et al, 2016 ). Although we could not determine the OPG after challenge, the number of shed oocysts might be small.…”