DNA measurements and ploidy determination of developmental stages in the life cycles ofTheileria annulata andT. parva

Abstract

The relative DNA levels of different developmental stages ofTheileria annulata andT. parva in the cow and the tick were measured by the cytophotometric DNA technique using the fluorochrome Hoechst 33258 as a staining dye. The results revealed that sporozoites, merozoites, gamonts, and gametes were haploid, whereas multinucleated intralymphocytic schizonts were polyploid. No difference was observed betweenT. parva andT. annulata in these stages. For bothTheileria species, the DNA measurements revealed that fusion of gametes occurred in the gut of the final host, thus providing evidence of sexual reproduction. However, differences were observed between the two parasites in the tick. WhereasT. parva zygotes underwent a two-step meiotic division, a comparable reduction division could not be unequivocally detected inT. annulata. Differences could also be detected in the further development of kinetes, indicating thatTheileria species are not characterized by only one life cycle, which is specific for this genus.