Abstract
BackgroundBabesiosis, a tick-borne disease caused by protozoans of the genus Babesia, is widespread in subtropical and tropical countries. Mitochondria are essential organelles that are responsible for energy transduction and metabolism, calcium homeostasis and cell signaling. Mitochondrial genomes could provide new insights to help elucidate and investigate the biological features, genetic evolution and classification of the protozoans. Nevertheless, there are limited data on the mitochondrial genomes of ovine Babesia spp. in China.MethodsHerein, we sequenced, assembled and annotated the mitochondrial genomes of six ovine Babesia isolates; analyzed the genome size, gene content, genome structure and cytochrome b (cytb) amino acid sequences and performed comparative mitochondrial genomics and phylogenomic analyses among apicomplexan parasites.ResultsThe mitochondrial genomes range from 5767 to 5946 bp in length with a linear form and contain three protein-encoding genes, cytochrome c oxidase subunit 1 (cox1), cytochrome c oxidase subunit 3 (cox3) and cytb, six large subunit rRNA genes (LSU) and two terminal inverted repeats (TIR) on both ends. The cytb gene sequence analysis indicated the binding site of anti-Babesia drugs that targeted the cytochrome bc1 complex. Babesia microti and Babesia rodhaini have a dual flip-flop inversion of 184–1082 bp, whereas other Babesia spp. and Theileria spp. have one pair of TIRs, 25–1563 bp. Phylogenetic analysis indicated that the six ovine Babesia isolates were divided into two clades, Babesia sp. and Babesia motasi. Babesia motasi isolates were further separated into two small clades (B. motasi Hebei/Ningxian and B. motasi Tianzhu/Lintan).ConclusionsThe data provided new insights into the taxonomic relationships and drug targets of apicomplexan parasites.
Highlights
Babesiosis, a tick-borne disease caused by protozoans of the genus Babesia, is widespread in subtropical and tropical countries
Sequence analysis Sequence analysis revealed that the ovine Babesia mitochondrial genomes were linear Deoxyribonucleic acid (DNA) of 5767 to 5946 bp, with 70.05–70.87% A + T content (Table 1)
The results showed that two sets of data from Sanger and Illumina have some differences in the size of the mitochondrial genome, the A + T contents, the number of large subunit rRNA genes (LSU), and the start and stop codons (Tables 1, 2, Additional file 3: Table S2) [32]
Summary
Babesiosis, a tick-borne disease caused by protozoans of the genus Babesia, is widespread in subtropical and tropical countries. There are limited data on the mitochondrial genomes of ovine Babesia spp. in China. The main causative agents in small ruminants are Babesia ovis and B. motasi, transmitted by the ticks Rhipicephalus spp. and Haemaphysalis spp. in Asia, South America, Africa, the Far East and Europe [1,2,3]. The six ovine Babesia parasites have different characteristics in serology, pathogenicity, vector specificity and virulence. BspXJ and BspDH have low virulence and are transmitted by Hyalomma spp. ticks, whereas the vector ticks of BmLT, BmHB, BmNX and BmTZ are Haemaphysalis spp. and cause a range of clinical manifestations. Were between 30.4–31.7 and 36.0–43.5%, respectively, which indicates that Babesia infection is prevalent in sheep and goats in China [11, 13,14,15] The prevalences of B. motasi and Babesia sp. were between 30.4–31.7 and 36.0–43.5%, respectively, which indicates that Babesia infection is prevalent in sheep and goats in China [11, 13,14,15]
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