Rapid Detection of Babesia motasi Responsible for Human Babesiosis by Cross-priming Amplification Combined with a Vertical Flow

Abstract

Background Babesia motasi is known as an etiological agent of human and ovine babesiosis. Diagnosis of babesiosis is traditionally performed by microscopy, examining Giemsa-stained thin peripheral blood smears. Rapid detection and accurate identification of species are desirable for clinical care and epidemiological studies. Methods An easy to operate molecular method, which requires less capital equipment and incorporates cross priming amplification combined with a vertical flow (CPA-VF) visualization strip for rapid detection and identification of B. motasi. Results The CPA-VF targets the 18S rRNA gene and has a detection limit of 50 fg per reaction; no cross reaction was observed with other piroplasms infective to sheep or Babesia infective to humans. CPA-VF and real-time (RT)-PCR had sensitivities of 95.2% (95% confidence interval [CI], 78.1-99.4%) and 90.5% (72-97.6%) and specificities of 95.8 (80.5-99.5%) and 97.9 (83.5-99.9%), respectively, versus microscopy and nested (n) PCR combined with gene sequencing. The clinical performance of the CPA-VF assay was evaluated with field blood samples from sheep (n = 240) in Jintai county, Gansu Province, and clinical specimens (n = 492) obtained from patients bitten by ticks. Conclusions Our results indicate that the CPA-VF is a rapid, accurate, nearly instrument-free molecular diagnostic approach for identification of B. motasi. Therefore, it could be an alternative technique for epidemiological investigations and diagnoses of ovine and/or human babesiosis caused by B. motasi, especially in resource-limited regions.