Development of a duplex real-time PCR assay for simultaneous detection and differentiation of Theileria equi and Babesia caballi.

Equine Piroplasmosis (EP) is a tick-borne disease caused by three apicomplexan protozoan parasites, Theileria equi (T. equi), Babesia caballi (B. caballi) and T. haneyi, which can cause similar clinical symptoms. There are five known 18S rRNA genotypes of T. equi group (including T. haneyi) and three of B. caballi. Real-time PCR methods for detecting EP based on 18S rRNA analysis have been developed, but these methods cannot detect all genotypes of EP in China, especially genotype A of T. equi. In this study, a duplex real-time PCR detection method was developed for the simultaneous detection and differentiation of T. equi and B. caballi. The primers and probes for this duplex real-time PCR assay were designed based on the conserved 18S rRNA gene sequences of all genotypes of T. equi and B. caballi including Chinese strain. Double-quenched probes were used in this method, which provide less background and more signal to decrease the number of false positives relative to single-quenched probes. The newly developed real-time PCR assays exhibited good specificity, sensitivity, repeatability and reproducibility. The real-time PCR assays were further validated by comparison with a nested PCR assay and a previous developed real-time PCR for EP and sequencing results in the analysis of 506 clinical samples collected from 2019 to 2020 in eleven provinces and regions of China. Based on clinical performance, the agreements between the duplex real-time PCR assay and the nPCR assay or the previous developed real-time PCR assay were 92.5% (T. equi) and 99.4% (B. caballi) or 87.4% (T. equi) and 97.2% (B. caballi). The detection results showed that the positivity rate of T. equi was 43.87% (222/506) (10 genotype A, 1 genotype B, 4 genotype C, 207 genotype E), while that of B. caballi was 5.10% (26/506) (26 genotype A), and the rate of T. equi and B. caballi co-infection was 2.40% (12/506). The established method could contribute to the accurate diagnosis, pathogenic surveillance and epidemiological investigation of T. equi and B. caballi infections in horses.

Babesiosis as a Cause of Atraumatic Splenic Injury: Two Case Reports and a Review of Literature.

We present two cases of Babesia-induced splenic injury at a single institution. In the late summer, two patients presented with left-sided abdominal pain radiating to the shoulder. They were both found to have hemolytic anemia, thrombocytopenia, and acute splenic infarction on imaging. Blood smears showed intracellular ring forms consistent with Babesia spp. and low parasitemia (<1%). Diagnosis was confirmed by PCR for Babesia microti. Both patients improved with azithromycin and atovaquone, without blood products or surgical intervention. Several weeks following treatment, repeat blood smears revealed no parasites. Splenic infarct and hemorrhage have been previously reported as rare complications of babesiosis. However, given the steady rise in Babesia microti cases in the USA, even these rare complications will become more prevalent. We review both the diagnosis and management of Babesia-induced splenic complications, which can be challenging in patients with low-level parasitemia. Clinicians should consider babesiosis as a cause of atraumatic splenic injury.