Hepatozoon ursi n. sp. (Apicomplexa: Hepatozoidae) in Japanese black bear ( Ursus thibetanus japonicus)

Abstract

Morphological and genetic features of a new Hepatozoon species, Hepatozoon ursi n. sp., in Japanese black bear ( Ursus thibetanus japonicus) were studied. Schizogonic developmental stages were observed in the lungs of Japanese black bears. The schizonts were sub-spherical in shape and 45.7 ± 4.6 × 42.7 ± 4.5 µm in size. Each mature schizont contained approximately 80–130 merozoites and 0–5 residual bodies. The merozoites were 7.0 ± 0.7 × 1.8 ± 0.3 µm in size. Intraleukocytic gametocytes were slightly curved, cigar-like in shape and had a beak-like protrusion at one end. The size of the gametocytes was 10.9 ± 0.3 × 3.3 ± 0.2 µm. The analyses of the18S rRNA gene sequences supported the hypothesis that H. ursi n. sp. is different from other Hepatozoon species. Mature Hepatozoon oocysts were detected in two species of ticks ( Haemaphysalis japonica and Haemaphysalis flava) collected on the bears infected with H. ursi n. sp. Two measured oocysts were 263.2 × 234.0 µm and 331.8 × 231.7 µm, respectively. The oocysts contained approximately 40 and 50 sporocysts, respectively. The sporocysts were sub-spherical in shape and 31.2 ± 2.5 × 27.0 ± 2.9 µm in size. Each sporocyst contained at least 8–16 sporozoites, with the sporozoites being 12.2 ± 1.4 × 3.5 ± 0.5 µm in size. H. ursi n. sp. is the first Hepatozoon species recorded from the family Ursidae.