Human babesiosis is a vector-borne disease caused by protozoan parasites of genus Babesia, such as B. duncani, B. microti, B. divergens, and B. venatorum (Lobo, Singh, & Rodriguez, 2020; Schnittger, Rodriguez, Florin-Christensen, & Morrison, 2012). The main transmission routes of Babesia include infected tick(ixodid) bites (Vannier, Diuk-Wasser, Ben Mamoun, & Krause, 2015; Young et al., 2019b), blood transfusion and transplacental transmission (Fox et al., 2006; Joseph et al., 2012). In recent years, increasing number of cases of human babesiosis have been reported in Asia, Africa, South America, North America, and Europe (Chen et al., 2019; Fang et al., 2015; Karshima, Karshima, & Ahmed, 2022; Krause, 2019; Man et al., 2016; Scott & Scott, 2018). B. duncani was first isolated from a patient in Washington State in 1991(Conrad et al., 2006a). At first, human cases of B. duncani were documented in the Western United States, mainly in Washington, Oregon and California. Nonetheless, till 2017, 1119 human cases of B. duncani infection have been identified across Canada (Scott & Scott, 2018).
It is reported that B. duncani present stronger pathogenicity and reproductive ability than B. microti (Wozniak, Lowenstine, Hemmer, Robinson, & Conrad, 1996), and even has strong resistance to the currently recommended antibabesia drugs (Abraham et al., 2018). So, the accurate diagnosis of B. duncani infection is important for making treatment regimen in patients (Conrad et al., 2006b; Young et al., 2019b) (O'Connor, Kjemtrup, Conrad, & Swei, 2018).The current molecular diagnostic methods for detecting B. duncani include nested-PCR(2018)(O'Connor et al., 2018), droplet digital PCR(2015)(Wilson et al., 2015), the Roche Molecular Systems(the cobas Babesia, 2021)(Stanley et al., 2021),and Nucleic Acid Testing(NAT)in use in the United States(Tonnetti, Dodd, Foster, & Stramer, 2022). These methods either need expensive equipment or have limited detection performance, which is not conducive to wide application. Due to the lack of effective diagnostic methods and the no symptoms in immune competent patients, the true infection status and distribution of the B. duncani is still unknown.
The number of reported cases of transmission through blood transfusions and naturally-acquired Babesia infections has increased in the last decade. In the United States, parasitic infections transmitted through blood transfusions are almost entirely caused by Babesia (Leiby, 2011a). However, blood screening for B. duncani is still lacking or only available in limited blood collection centers (Busch, Bloch, & Kleinman, 2019). Therefore, blood screening in blood donors is required to prevent TTB caused by B. duncani in areas where B. duncani is endemic, such as the Canada and United States (Wagner, Leiby, & Roback, 2019).
Human babesiosis caused by B. duncani has gradually become a public health problem and has the potential to spread continuously in new areas, so regular monitoring and effective intervention are required to prevent further spreading and development of this pathogen. Therefore, there is an urgent need to develop and validate a rapid, effective and reliable diagnostic method for the specific identification of B. duncani. The aim of this study was to develop a reliable diagnostic technique to identify B. duncani infection in humans and animals.