BABESIA MICROTI INFECTION WITH LOW-GRADE PARASITEMIA CAUSING ARDS IN AN IMMUNOCOMPETENT PATIENT

SESSION TITLE: Unusual Critical Care SESSION TYPE: Rapid Fire Case Reports PRESENTED ON: 10/18/2022 10:15 am - 11:10 am INTRODUCTION: Babesiosis can have a clinical spectrum ranging from mild illness in most cases to more severe manifestations in immunosuppressed individuals or in those with high-grade parasitemia. This patient had severe babesiosis resulting in ARDS and shock in spite of being immunocompetent and having low-grade parasitemia, making it a rare presentation. CASE PRESENTATION: A 49-year-old, previously healthy woman, was admitted with high-grade fevers. Physical exam findings were normal, except for fever (103 F). Initial lab results were significant for hemolytic anemia and thrombocytopenia. Chest radiography was normal. Other microbiology studies, including COVID-19, were negative. Empiric antibiotic therapy with piperacillin-tazobactam and doxycycline was started. Peripheral smear identified rare, minute intracellular ring forms, suspicious for babesia. IV azithromycin and oral atovaquone were started. PCR was done to confirm the diagnosis and Babesia microti DNA was detected. As peripheral smear showed parasitemia of only 1% (percentage of red blood cells infected), exchange transfusion was not considered as a treatment option. Two days after admission, worsening hemodynamic and respiratory status was noted with increasing oxygen requirements. CT chest now revealed diffuse interstitial infiltrates. ARDS ensued and the patient was intubated and started on mechanical ventilation with vasopressor support. Immunodeficiency workup was normal. In view of clinical deterioration, the antimicrobials were switched from atovaquone and azithromycin to IV clindamycin and quinidine for 14 days. After a protracted ICU stay, the patient showed gradual clinical improvement, parasitemia resolved, and she was eventually discharged to a rehabilitation facility. DISCUSSION: Babesiosis is a tick-borne infectious disease endemic to the North-East and Midwest United States. Majority of the infections are self-limited. However, in immunocompromised individuals and in those with high-grade parasitemia (>10%), it manifests as a severe illness with ARDS, severe hemolysis, or shock. Diagnosis is made by identifying parasites on thin peripheral blood smears with Giemsa/Wright stains. PCR can be used for species identification and for confirming the diagnosis in cases with low-grade parasitemia (<4%). IV azithromycin plus oral atovaquone is the preferred initial regimen and IV clindamycin plus quinidine is an alternative combination that can be used in severe infection. Red blood cell exchange transfusion can be considered in patients with high-grade parasitemia or organ failure. CONCLUSIONS: Babesiosis can very rarely cause ARDS and shock in immunocompetent patients with low-grade parasitemia. Prompt diagnosis and escalation of antimicrobial regimens to clindamycin and quinidine in such cases can lead to improved clinical outcomes. Exchange transfusion can serve as a treatment option in patients with high-grade parasitemia. Reference #1: Ord RL, Lobo CA. Human babesiosis: Pathogens, prevalence, diagnosis, and treatment. Current clinical microbiology reports. 2015 Dec;2(4):173-81. Reference #2: Ripoll JG, Rizvi MS, King RL, Daniels CE. Severe Babesia microti infection presenting as multiorgan failure in an immunocompetent host. Case Reports. 2018 May 30;2018:bcr-2018. Reference #3: Sanchez E, Vannier E, Wormser GP, Hu LT. Diagnosis, treatment, and prevention of Lyme disease, human granulocytic anaplasmosis, and babesiosis: a review. Jama. 2016 Apr 26;315(16):1767-77. DISCLOSURES: No relevant relationships by Shankar Chhetri No relevant relationships by Vasudev Malik Daliparty No relevant relationships by Preethi Dendi No relevant relationships by samer talib

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.

Challenges and Promises for Obtaining New Antiprotozoal Drugs: What’s Going Wrong?

Infections by protozoa can cause some of the most serious human diseases, particularly in tropical regions. However, the number of available drugs used to treat such diseases tends to be limited with relatively high toxicity, and the vast majority of such drugs were developed in the 1920s to 1970s. The development of antiprotozoal drugs has been hindered owing in part to: (1) the highly complicated life cycles of such organisms and their ability to avoid innate immune defences;(2) challenges associated with culturing such organisms particularly in different phases of their growth and amplification;and (3) a lack of investment in biomedical research aimed at developing treatments for tropical diseases that do not tend to affect more affluent countries. Indeed, only three new drugs have entered into clinical trials in recent times, highlighting the tremendous gap in knowledge that should be bridged to more effectively treat protozoal infections.