Antigenic and Genetic Diversities of Babesia ovata in Persistently Infected Cattle.

Abstract

ABSTRACT. Exploring the antigenic and genetic diversities of Babesia ovata, we obtained several field isolates from grazing cattle in the Okushiri island, Japan. Parasite isolation was greatly facilitated by using bovine red blood cell-substituted SCID mice (Bo-RBC-SCID mice), into which the blood samples of the cattle were inoculated. Isolates from different individuals within a herd of cattle were compared in immunoblot analysis with an anti-B. ovata serum and also in Southern blot analysis with a probe for the small subunit ribosomal RNA gene. In both analyses, the isolates exhibited banding patterns that were significantly different from each other. We were also able to obtain a series of parasite isolates from a single cow in different seasons of a nine months period, including winter when active vector ticks were not in the field environment. Different seasonal isolates showed different banding patterns in both immunoblot and Southern blot analyses. By contrast, these analyses detected little difference among the parasites that had been passed various times in Bo-RBC-SCID mice, where no specific immune responses should be generated. These results indicate that individual animals within a herd of cattle were infected with antigenically and genetically diversified populations of B. ovata, and that the parasites could persistently infect a single animal with dynamic change in their predominant subpopulations. -KEY WORDS: Babesia ovata, diversity, persistent infection.

A PCR Based Survey of <i>Babesia ovata</i> in Cattle from Various Asian, African and South American Countries

“…In contrast to other bovine hemoprotozoan parasites, the prevalence of B. ovata was lower. B. ovata maintains a low parasitemia in infected cattle so that immune responses are kept at a minimum level, thereby ensuring survival of the parasite [3]. Therefore, there is the possibility that bovine DNA samples might contain a very low concentration of B. ovata DNA, which cannot be detected by PCR.…”

“…However, parasitemia of B. ovata in infected cattle tends to be very low making microscopy difficult [3]. Furthermore, as the morphology among many large Babesia parasites is similar, microscopy is not an effective diagnostic tool for species differentiation [5].…”

PCR Detection of Babesia ovata from Cattle Reared in Japan and Clinical Significance of Coinfection with Theileria orientalis

“…he benign group of Theileria parasites (Theileria sergenti, Theileria buffeli, and Theileria orientalis) and Babesia ovata constitute the only bovine piroplasms that are known to be endemic in Japan (1,7,13). T. orientalis is not considered to be highly pathogenic; however, clinical signs of anemia have sometimes been observed in cattle affected by this parasite (5,8).…”

Retrospective Seroepidemiological Survey for Human Babesiosis in an Area in Japan Where a Tick-Borne Disease is Endemic.

“…Western blot analysis: The procedure of Western blot analysis has been described previously [1,23]. Babesiainfected erythrocytes were lysed at 4°C in a solution consisting of 10 mM Tris-HCl and 10 mM EDTA (pH 7.5), followed by centrifugation at 10,000 × g for 10 min.…”