A sero-epidemiological survey of Chinese Babesia motasi for small ruminants in China.

Babesia motasi BQ1 (Lintan) was first isolated from Haemaphysalis qinghaiensis collected in Gannan Tibet Autonomous Region, Gansu province in April 2000. In this study, a total of 3,204 serum samples from small ruminants in 22 provinces located in different districts of China were tested for antibodies against merozoite antigens from cultured B. motasi BQ1 (Lintan) by enzyme-linked immunosorbent assay. This method can survey the prevalence of low-pathogenic Chinese B. motasi. The results of this survey indicated that the average positive rate was 43.5 %, and the positive rates of investigated provinces were significantly different from 6.1 to 91.0 %, and the infections had been found in all provinces investigated. Our data provide large important information regarding the current sero-prevalence of B. motasi in China.

Merozoite proteins from Babesia sp. BQ1 (Lintan) as potential antigens for serodiagnosis by ELISA.

Babesia sp. BQ1 (Lintan) is a Babesia isolated from sheep infested with Haemaphysalis qinghaiensis in China, and is closely related to B. motasi based on the 18S rRNA gene sequence. In the present study, an ELISA was developed with merozoite antigens of Babesia sp. BQ1 (Lintan) (BQMA) purified from in vitro culture. When the positive threshold was chosen as 30% of the antibodies rate, evaluated with 198 negative sera, the specificity was 95.5%. Except for Babesia sp. Tianzhu, there was no cross-reaction between BQMA and positive sera from Babesia sp. BQ1 (Ningxian)-, Babesia sp. Hebei-, Babesia sp. Xinjiang-, Theileria luwenshuni-, T. uilenbergi-, or Anaplasma ovis-infected sheep, which are the dominant haemoparasites of small ruminants in China. Specific antibodies against Babesia sp. BQ1 (Lintan) were produced 1 or 2 weeks post-infection and a high level of antibodies persisted for more than 8 months in experimentally infected sheep. This ELISA was tested on 974 sera collected from field-grazing sheep in 3 counties of Gansu province, northwestern China to evaluate the seroprevalence of Babesia sp. BQ1 (Lintan) infection and the average positive rate was 66.84%. The feasibility of increasing the specificity of this BQMA-based ELISA, by using some BQMA antigens for serodiagnosis is discussed.

At least two genetically distinct large Babesia species infective to sheep and goats in China.

A fatal disease of sheep and goats in the northern part of China has been reported to be due to Babesia ovis. However, some characteristics of the causative agent in recent reports are not in accordance with the original attributes ascribed to this parasite. Therefore, the 18S small subunit ribosomal RNA (18S rRNA) genes of a number of Babesia isolates in China were sequenced and compared with that of other Babesia and Theileria species in an attempt to clarify their taxonomic position. In the present study, seven Babesia isolates were collected from distinct areas of northern China, and the 18S rRNA genes were amplified and sequenced. The phylogenetic trees were inferred based on 18S rRNA gene sequences of the Chinese ovine Babesia isolates and some of ovine Babesia and Theileria species available in GenBank. In the phylogenetic tree, Babesia sp. isolates from Madang, Tianzhu, Lintan, Ningxian, Hebei and Liaoning all grouped with B. motasi with 88.2-99.9% identity, while Babesia sp. Xinjiang grouped in a separate clade between B. ovis and B. crassa with 79.7-81.2% identity. The results indicated that there are at least two distinct Babesia species groups-B. motasi and Babesia sp. Xinjiang, the latter was distinctly different from other ovine Babesia isolates from China with less than 86.6% identity.

Pharmacokinetics of ivermectin in the yak (Bos grunniens).

The yak (Bos grunniens) belongs to the cattle family Bovidae and lives in the mountains of China and adjacent areas. Due to the physiological adaptations of yak to its environment and the lack of data, the ivermectin pharmacokinetic was studied following a single subcutaneous dose at the recommended dose for cattle (0.2 mg kg(-1)). The observed peak plasma concentration (Cmax) was 48.93 ng ml(-1) and the time to reach Cmax (Tmax) was 0.73 day. These results show a faster rate of absorption than in cattle. The values for the absorption half-life (t(1/2a)), the distribution half-life (t(1/2alpha)) and the terminal half-life (t(1/2beta)) were 0.31, 0.74 and 4.82 days, respectively. The calculated area under the concentration-time curve (AUC) was 146.2 ng day ml(-1) and the mean residence time (MRT) was 3.57 days. The availability of ivermectin appears low in yaks in comparison to cattle but equivalent to that reported in horses and is likely to be due to physiological characteristics of this species.

Transmission of Babesia sp to sheep with field-collected Haemaphysalis qinghaiensis.

Haemaphysalis qinghaiensis ticks collected in the Gannan Tibet Autonomous Region were infested onto a sheep from a Babesia-free area. A strain of small Babesia (1.8-2.1 microm in length) was isolated from the sheep. Most of the Babesia in erythrocytes were round, oval, single pyriform, double pyriform, budding or elongated in form. Measurements were made of 100 single sides of the double-pyriform Babesia and compared with those for B. motasi and B. ovis from Holland, using Student's t-test. The Gannan small Babesia was similar to the B. ovis from Holland, but differed significantly from the Dutch B. motasi.

Development of an enzyme-linked immunosorbent assay for the diagnosis of Theileria sp. infection in sheep.

A rapid, sensitive and specific diagnostic method, an enzyme-linked immunosorbent assay (ELISA), was developed for the diagnosis of Theileria sp. infection in sheep; and optimal conditions were established, such as antigen concentration, serum dilution, coating time, Tween-20 concentration and conjugate. The results were analyzed by measuring the coefficient of variation (CV). Three sera titers (high, middle, low) were analyzed over the measurement range, resulting in a CV of around 10%, whereas a 30% variation is the maximum acceptable. The cut-off value was determined by the mean of a negative control plus three standard deviations. Cross-reaction was found only with Babesia ovis. However, this result may be questionable, because it cannot be excluded that these sheep were already infected with both Theileria sp. and B. ovis. The ELISA described in the present study proved to be a useful tool for studying the epidemiology of Theileria sp.