Life cycle of Eimeria vejdovskyi Pakandl, 1988: electron microscopy study

Abstract

The endogenous development of the rabbit coccidium Eimeria vejdovskyi was studied in SPF rabbits using light and electron microscopy. All endogenous stages were seen in the ileal epithelium. There were two types of meronts in each of five asexual generations. Type A produced fat, polynucleate merozoites while type B meronts had slender uninucleate merozoites. First- second- and third-generation meronts were in the crypts. The first meronts were at the bottom of the crypts, very often in the Paneth cells. The meronts of the fourth generation were in the middle of the villi; the fifth-generation meronts were recorded in the middle and at the top of the villi. The prepatent period was 10 days.

Coccidia of rabbit: a review

“…This was observed in E. intestinalis ), E. piriformis (Pakandl and Jelínková 2006), and E. vejdovskyi (Pakandl and Coudert 1999). In this case, the second and sometimes the following generation meronts plentifully occur in one crypt, whereas often no parasite stages are found in the neighbouring crypts, as the merozoites arising from the first generation probably do not migrate far and enter host cells in their proximity, giving rise to the next AG.…”

“…Such merozoites differ from uninucleate ones in number of nuclei and in the presence of some structures belonging to newly formed merozoites, namely inner membranous complex, rhoptry anlage and, sometimes, conoid (Danforth andHammond 1972, Pakandl et al 1996a). The polynucleate merozoites resemble "sporozoite-like schizonts" found in the rabbit coccidia E. magna (Pakandl et al 1996b), E. media (Pakandl et al 1996c), E. vejdovskyi (Pakandl and Coudert 1999) and E. flavescens (Pakandl 2005). This stage develops from a sporozoite, in which characteristic organelles such as three-layered pellicle and apical complex are conserved, but nuclear division and the initial formation of merozoites already begins.…”

“…The fact that the microgamonts are less numerous than macrogamonts is inherent with this observation. The same is applicable for E. flavescens (Pakandl et al 2003), E. intestinalis ), E. magna (Pakandl et al 1996b) E. media (Pakandl et al 1996c), and E. vejdovskyi (Pakandl and Coudert 1999). Moreover, the suppression of the fourth AG, in which type B meronts give rise to larger numbers of merozoites than those of type A, in the precocious line of E. flavescens resulted in the enhanced proportions of type A meronts in the fifth AG and microgamonts as compared with those of the parent strain.…”

“…Two coccidia are able to produce more oocysts per rabbit: E. vejdovskyi 10-15 × 10 8 and E. intestinalis 30-50 × 10 8 . Perhaps the localisation of gamogony in the villi of the lower part of the small intestine enhances the total oocyst output, since gamogony of E. vejdovskyi takes place in the villi of the ileum (Pakandl and Coudert 1999) and E. intestinalis parasitizes in the lower jejunum and ileum in both crypts and villi (Peeters et al 1984a. Not surprisingly, the life cycle characterised by the number of AG and the number of merozoites produced by type B meronts in each generation influences the prepatent period (PP) and reproductive potential (RP) characterised by the oocyst yield for one oocyst inoculated to one rabbit.…”

“…For example, there are only two and three AG in the life cycle of E. perforans (Streun et al 1979) and E. media (Pakandl et al 1996c), respectively, and these species have the shortest PP: 5 (E. perforans) and 4.5 (E. media) days. In contrast, E. vejdovskyi, the rabbit intestinal coccidium with the longest PP (10 days), forms five AG during its endogenous development (Pakandl and Coudert 1999) and the liver coccidium E. stiedai with PP 14 days has 5-6 AG in its life cycle (Pellérdy and Dürr 1970).…”