Phylogeny of sheep and goat Theileria and Babesia parasites

Abstract

The phylogenetic relationship of Theileria and Babesia species infecting sheep and goats on the basis of their 18S RNA gene structure was addressed in the present study. For this purpose, the complete sequences of the small ribosomal RNA genes of a panel of sheep and goat piroplasm isolates, including T. lestoquardi, T. ovis, T. separata, B. ovis, B. motasi, B. crassa and several novel species, were sequenced and compared. The classification based on the established phylogenetic tree corresponded with traditional systematics and revealed that sheep/goat piroplasm species are of polyphyletic origin. The independent evolution of almost all sheep/goat piroplasms suggests that speciation may have occurred after transfer of the piroplasm-transmitting tick from a primal wild ruminant host to domestic sheep and goats. In accordance with recent reports, our study confirms the existence of at least two additional sheep/goat piroplasm species, designated Theileria sp. 1 (China) and Theileria sp. 2 (China). The recently reported pathogenic sheep/goat Theileria sp. 1 (China) seems to be identical with a Theileria sp. isolated from Japanese serow. Furthermore, our results suggest that T. ovis represents a single species.

Isolation and characterization of Babesia pecorum sp. nov. from farmed red deer (Cervus elaphus)

“…Xinjiang from sheep in China are variants of the same species [26]. In the present study, the identities of the 18S rRNA gene sequences of the members of this group were all higher than 96.6% (over 98.3%), and they could thus be considered as variants of the same species according to [40]. However, we strongly believe that the assignment of an isolate to a species on the basis of sequence data must also be correlated with biological characteristics.…”

“…Species delineation on the basis of sequence identities is controversial, and there is no rule about the level of genetic difference on a particular gene that defines a species. In their study of the phylogeny of Babesia from sheep and goat, Schnittger et al [40] estimated that, within the genus Babesia , isolates with an 18S rRNA gene identity higher than 97.6% should be considered as belonging to the same species. In the same study, isolates were considered as belonging to separate species when this identity was less than 96.6%.…”

Identification of Tick-Borne Pathogens in Ticks Feeding on Humans in Turkey

“…AY260177) obtained from a sheep in Turkey (Table 2). Although the other B. crassa was detected from a sheep previously in Turkey, the detected area information was not provided [38]. However, it is clear that B. crassa exists in both ticks and sheep in Turkey.…”

A review of Theileria diagnostics and epidemiology

“…Another “species” that belongs to this group is T. sinensis (Bai et al., 2002). The genotypes from this clade were postulated to be in the process of speciation that has not been completed yet (Schnittger et al., 2003), while others considered members to be distinct species (Kawazu et al., 1992; Fujisaki et al., 1994). Most members of this group are considered to be benign, but a recent outbreak of a virulent genotype (Ikeda type) in Australia readdressed the possibility of unique species in this group (Izzo et al., 2010; Kamau et al., 2011).…”