Human babesiosis

A novel and low-cost cross-priming amplification assay for rapid detection of Babesia duncani infection

Babesia duncani, responsible for human babesiosis, is one of the most important tick-borne intraerythrocytic pathogens. Traditionally, babesiosis is definitively diagnosed by detecting parasite DNA in blood samples and examining Babesia parasites in Giemsa-stained peripheral blood smears. Although these techniques are valuable for determining Babesia duncani, they are often time-consuming and laborious. Therefore, developing rapid and reliable B. duncani identification assays is essential for subsequent epidemiological investigations and prevention and control. In this study, a cross-priming amplification (CPA) assay was developed, combined with a vertical flow visualization strip, to rapidly and accurately detect B. duncani infection. The detection limit of this method was as low as 0.98 pg/μl of genomic DNA from B. duncani merozoites per reaction at 59 °C for 60 min. There were no cross-reactions between B. duncani and other piroplasms infective to humans and mammals. A total of 592 blood samples from patients bitten by ticks and experimental infected hamsters were accurately assessed using CPA assay. The average cost of the CPA assay is as low as approximately $ 0.2 per person. These findings indicate that the CPA assay may therefore be a rapid screening tool for detection B. duncani infection, based on its accuracy, speed, and cost-effectiveness, particularly in resource-limited regions with a high prevalence of human babesiosis.

Tafenoquine for Relapsing Babesiosis: A Case Series

BACKGROUND

Relapsing babesiosis often occurs in highly immunocompromised patients and has been attributed to the acquisition of resistance against drugs commonly used for treatment such as atovaquone, azithromycin, and clindamycin. Tafenoquine, which is approved for malaria prophylaxis and presumptive antirelapse treatment of Plasmodium vivax malaria, has shown activity against Babesia microti in several animal models of acute infection and in a single human case of relapsing babesiosis. Here, we report 5 cases of relapsing babesiosis treated with tafenoquine, including the previous case, and begin to define the conditions for optimal use of tafenoquine in relapsing babesiosis.

METHODS

A definitive diagnosis of babesiosis was made by microscopic examination of Giemsa-stained thin blood smears or a real-time polymerase chain reaction (PCR) that targets the parasite 18S rRNA gene. Clearance of B. microti infection was ascertained by use of blood smear and real-time PCR.

RESULTS

Tafenoquine was initiated with a loading dose of 600 mg. A weekly maintenance dose consisted of 200 mg or 300 mg; the lower dose was associated with a delayed clearance of B. microti. In 2 cases, all antimicrobial agents but tafenoquine were discontinued prior to clearance of infection. In 2 other cases, clearance was achieved while tafenoquine was administered along with other antimicrobial agents. In 3 of these 4 cases, tafenoquine was used in combination with atovaquone-proguanil. Other agents included atovaquone, azithromycin, and/or clindamycin. In 1 case, tafenoquine was administered alone and failed to prevent relapse.

CONCLUSIONS

Tafenoquine can be a useful adjunct for the treatment of highly immunocompromised patients experiencing relapsing babesiosis caused by B. microti.

Human Babesia odocoilei and Bartonella spp. co-infections in the Americas

BACKGROUND

In recent years, Babesia and Bartonella species co-infections in patients with chronic, nonspecific illnesses have continued to challenge and change the collective medical understanding of "individual pathogen" vector-borne infectious disease dynamics, pathogenesis and epidemiology. The objective of this case series is to provide additional molecular documentation of Babesia odocoilei infection in humans in the Americas and to emphasize the potential for co-infection with a Bartonella species.

METHODS

The development of improved and more sensitive molecular diagnostic techniques, as confirmatory methods to assess active infection, has provided increasing clarity to the healthcare community.

RESULTS

Using a combination of different molecular diagnostic approaches, infection with Babesia odocoilei was confirmed in seven people suffering chronic non-specific symptoms, of whom six were co-infected with one or more Bartonella species.

CONCLUSIONS

We conclude that infection with Babesia odocoilei is more frequent than previously documented and can occur in association with co-infection with Bartonella spp.

Identification of Babesia microti immunoreactive antigens by phage display cDNA screen

Human babesiosis is a malaria-like illness caused by protozoan parasites of the genus Babesia. Babesia microti is responsible for most cases of human babesiosis in the United States, particularly in the Northeast and the Upper Midwest. Babesia microti is primarily transmitted to humans through the bite of infected deer ticks but also through the transfusion of blood components, particularly red blood cells. There is a high risk of severe and even fatal disease in immunocompromised patients. To date, serology testing relies on an indirect immunofluorescence assay that uses the whole Babesia microti antigen. Here, we report the construction of phage display cDNA libraries from Babesia microti-infected erythrocytes as well as human reticulocytes obtained from donors with hereditary hemochromatosis. Plasma samples were obtained from patients who were or had been infected with Babesia microti. The non-specific antibody reactivity of these plasma samples was minimized by pre-exposure to the human reticulocyte library. Using this novel experimental strategy, immunoreactive segments were identified in three Babesia microti antigens termed BmSA1 (also called BMN1-9; BmGPI12), BMN1-20 (BMN1-17; Bm32), and BM4.12 (N1-15). Moreover, our findings indicate that the major immunoreactive segment of BmSA1 does not overlap with the segment that mediates BmSA1 binding to mature erythrocytes. When used in combination, the three immunoreactive segments form the basis of a sensitive and comprehensive diagnostic immunoassay for human babesiosis, with implications for vaccine development.

Tick-Borne Diseases

Ticks are responsible for the vast majority of vector-borne illnesses in the United States. The number of reported tick-borne disease (TBD) cases has more than doubled in the past 20 years. The majority of TBD cases occur in warm weather months in individuals with recent outdoor activities in wooded areas. The risk of contracting a TBD is also highly dependent on geographic location. Between 24 and 48 hours of tick attachment is required for most disease transmission to occur. Only 50% to 70% of patients with a TBD will recall being bitten by a tick, and TBDs are often initially misdiagnosed as a viral illness. Most TBDs are easily treated when diagnosed early in their course.

Great genetic diversity of vector-borne bacteria and protozoan in wild rodents from Guangxi, China

BACKGROUND

Rodents are recognized as the hosts of many vector-borne bacteria and protozoan parasites and play an important role in their transmission and maintenance. Intensive studies have focused on their infections in vectors, especially in ticks, however, vector-borne bacterial and protozoan infections in rodents are poorly understood although human cases presenting with fever may due to their infection have been found.

METHODS

From May to October 2019, 192 wild rodents were trapped in wild environment of Guangxi Province, and the spleen samples were collected to reveal the presence of vector-borne bacterial and protozoan infections in them. The microorganisms in rodents were identified by detecting their DNA using (semi-)nested PCR. All the PCR products of the expected size were subjected to sequencing, and then analyzed by BLASTn. Furthermore, all the recovered sequences were subjected to nucleotide identity and phylogenetic analyses.

RESULTS

As a result, 192 rodents representing seven species were captured, and Bandicota indica were the dominant species, followed by Rattus andamanensis. Based on the (semi-)nested PCR, our results suggested that Anaplasma bovis, Anaplasma capra, Anaplasma ovis, Anaplasma phagocytophilum, "Candidatus Neoehrlichia mikurensis", "Candidatus E. hainanensis", "Candidatus E. zunyiensis", three uncultured Ehrlichia spp., Bartonella coopersplainsensis, Bartonella tribocorum, Bartonella rattimassiliensis, Bartonella silvatica, two uncultured Bartonella spp., Babesia microti and diverse Hepatozoon were identified in six rodent species. More importantly, six species (including two Anaplasma, two Bartonella, "Ca. N. mikurensis" and Bab. microti) are zoonotic pathogens except Anaplasma bovis and Anaplasma ovis with zoonotic potential. Furthermore, dual infection was observed between different microorganisms, and the most common type of co-infection is between "Ca. N. mikurensis" and other microorganisms. Additionally, potential novel Bartonella species and Hepatozoon species demonstrated the presence of more diverse rodent-associated Bartonella and Hepatozoon.

CONCLUSIONS

The results in this work indicated great genetic diversity of vector-borne infections in wild rodents, and highlighted the potential risk of human pathogens transmitted from rodents to humans through vectors.

Effectiveness of Two New Endochin-like Quinolones, ELQ-596 and ELQ-650, in Experimental Mouse Models of Human Babesiosis

Endochin-like quinolones (ELQs) define a class of small molecule antimicrobials that target the mitochondrial electron transport chain of various human parasites by inhibiting their cytochrome bc1 complexes. The compounds have shown potent activity against a wide range of protozoan parasites, including the intraerythrocytic parasites Plasmodium and Babesia, the agents of human malaria and babesiosis, respectively. First-generation ELQ compounds were previously found to reduce infection by Babesia microti and Babesia duncani in animal models of human babesiosis but achieved a radical cure only in combination with atovaquone and required further optimization to address pharmacological limitations. Here, we report the identification of two second-generation 3-biaryl ELQ compounds, ELQ-596 and ELQ-650, with potent antibabesial activity in vitro and favorable pharmacological properties. In particular, ELQ-598, a prodrug of ELQ-596, demonstrated high efficacy as an orally administered monotherapy at 10 mg/kg. The compound achieved radical cure in both the chronic model of B. microti-induced babesiosis in immunocompromised mice and the lethal infection model induced by B. duncani in immunocompetent mice. Given its high potency, favorable physicochemical properties, and low toxicity profile, ELQ-596 represents a promising drug for the treatment of human babesiosis.

Absence of Anti-Babesia microti antibody in commercial intravenous immunoglobulin (IVIG)

BACKGROUND

Babesiosis is a worldwide emerging protozoan infection that is associated with a spectrum of disease severity from asymptomatic infection to severe organ damage and death. While effective treatment strategies are available, some immunocompromised patients experience severe acute and prolonged/relapsing illness due in part to an impaired host antibody response. Intravenous immunoglobulin (IVIG) has been used as an adjunctive therapy in some immunocompromised babesiosis patients, but its therapeutic effect is uncertain. We evaluated the presence of Babesia microti antibodies in commercial samples of IVIG.

METHODS/PRINCIPLE FINDINGS

The presence of B. microti antibodies in commercial samples of IVIG were tested using an immunofluorescence assay. A subset of samples was then tested for B. microti antibodies using an enzyme linked immunosorbent assay. Out of 57 commercial IVIG samples tested using IFA, and 52 samples tested using ELISA, none were positive for B. microti antibodies.

CONCLUSIONS

Commercially available IVIG may not be of therapeutic benefit for babesiosis patients. Additional sampling of IVIG for B. microti antibody and a clinical trial of babesiosis patients given IVIG compared with controls would provide further insight into the use of IVIG for the treatment of babesiosis.

Quercetin as a Promising Antiprotozoan Phytochemical: Current Knowledge and Future Research Avenues

Despite tremendous advances in the prevention and treatment of infectious diseases, only few antiparasitic drugs have been developed to date. Protozoan infections such as malaria, leishmaniasis, and trypanosomiasis continue to exact an enormous toll on public health worldwide, underscoring the need to discover novel antiprotozoan drugs. Recently, there has been an explosion of research into the antiprotozoan properties of quercetin, one of the most abundant flavonoids in the human diet. In this review, we tried to consolidate the current knowledge on the antiprotozoal effects of quercetin and to provide the most fruitful avenues for future research. Quercetin exerts potent antiprotozoan activity against a broad spectrum of pathogens such as Leishmania spp., Trypanosoma spp., Plasmodium spp., Cryptosporidium spp., Trichomonas spp., and Toxoplasma gondii. In addition to its immunomodulatory roles, quercetin disrupts mitochondrial function, induces apoptotic/necrotic cell death, impairs iron uptake, inhibits multiple enzymes involved in fatty acid synthesis and the glycolytic pathways, suppresses the activity of DNA topoisomerases, and downregulates the expression of various heat shock proteins in these pathogens. In vivo studies also show that quercetin is effective in reducing parasitic loads, histopathological damage, and mortality in animals. Future research should focus on designing effective drug delivery systems to increase the oral bioavailability of quercetin. Incorporating quercetin into various nanocarrier systems would be a promising approach to manage localized cutaneous infections. Nevertheless, clinical trials are needed to validate the efficacy of quercetin in treating various protozoan infections.

Comparative chemical genomics in Babesia species identifies the alkaline phosphatase PhoD as a determinant of antiparasitic resistance

Babesiosis is an emerging zoonosis and widely distributed veterinary infection caused by 100+ species of Babesia parasites. The diversity of Babesia parasites and the lack of specific drugs necessitate the discovery of broadly effective antibabesials. Here, we describe a comparative chemogenomics (CCG) pipeline for the identification of conserved targets. CCG relies on parallel in vitro evolution of resistance in independent populations of Babesia spp. (B. bovis and B. divergens). We identified a potent antibabesial, MMV019266, from the Malaria Box, and selected for resistance in two species of Babesia. After sequencing of multiple independently derived lines in the two species, we identified mutations in a membrane-bound metallodependent phosphatase (phoD). In both species, the mutations were found in the phoD-like phosphatase domain. Using reverse genetics, we validated that mutations in bdphoD confer resistance to MMV019266 in B. divergens. We have also demonstrated that BdPhoD localizes to the endomembrane system and partially with the apicoplast. Finally, conditional knockdown and constitutive overexpression of BdPhoD alter the sensitivity to MMV019266 in the parasite. Overexpression of BdPhoD results in increased sensitivity to the compound, while knockdown increases resistance, suggesting BdPhoD is a pro-susceptibility factor. Together, we have generated a robust pipeline for identification of resistance loci and identified BdPhoD as a resistance mechanism in Babesia species.

Automatic patient-level recognition of four Plasmodium species on thin blood smear by a real-time detection transformer (RT-DETR) object detection algorithm: a proof-of-concept and evaluation

Malaria remains a global health problem, with 247 million cases and 619,000 deaths in 2021. Diagnosis of Plasmodium species is important for administering the appropriate treatment. The gold-standard diagnosis for accurate species identification remains the thin blood smear. Nevertheless, this method is time-consuming and requires highly skilled and trained microscopists. To overcome these issues, new diagnostic tools based on deep learning are emerging. This study aimed to evaluate the performances of a real-time detection transformer (RT-DETR) object detection algorithm to discriminate Plasmodium species on thin blood smear images. The algorithm was trained and validated on a data set consisting in 24,720 images from 475 thin blood smears corresponding to 2,002,597 labels. Performances were calculated with a test data set of 4,508 images from 170 smears corresponding to 358,825 labels coming from six French university hospitals. At the patient level, the RT-DETR algorithm exhibited an overall accuracy of 79.4% (135/170) with a recall of 74% (40/54) and 81.9% (95/116) for negative and positive smears, respectively. Among Plasmodium-positive smears, the global accuracy was 82.7% (91/110) with a recall of 90% (38/42), 81.8% (18/22), and 76.1% (35/46) for P. falciparum, P. malariae, and P. ovale/vivax, respectively. The RT-DETR model achieved a World Health Organization (WHO) competence level 2 for species identification. Besides, the RT-DETR algorithm may be run in real-time on low-cost devices such as a smartphone and could be suitable for deployment in low-resource setting areas lacking microscopy experts.IMPORTANCEMalaria remains a global health problem, with 247 million cases and 619,000 deaths in 2021. Diagnosis of Plasmodium species is important for administering the appropriate treatment. The gold-standard diagnosis for accurate species identification remains the thin blood smear. Nevertheless, this method is time-consuming and requires highly skilled and trained microscopists. To overcome these issues, new diagnostic tools based on deep learning are emerging. This study aimed to evaluate the performances of a real-time detection transformer (RT-DETR) object detection algorithm to discriminate Plasmodium species on thin blood smear images. Performances were calculated with a test data set of 4,508 images from 170 smears coming from six French university hospitals. The RT-DETR model achieved a World Health Organization (WHO) competence level 2 for species identification. Besides, the RT-DETR algorithm may be run in real-time on low-cost devices and could be suitable for deployment in low-resource setting areas.

The protective effects of BMSA1 and BMSA5-1-1 proteins against Babesia microti infection

The intracellular parasite Babesia microti is among the most significant species causing human babesiosis and is an emerging threat to human health worldwide. Unravelling the pathogenic molecular mechanisms of babesiosis is crucial in developing new diagnostic and preventive methods. This study assessed how priming with B. microti surface antigen 1 (BHSA 1) and seroreactive antigen 5-1-1 (BHSA 5-1-1) mediate protection against B. microti infection. The results showed that 500 µg/ml rBMSA1 and rBMSA5-1-1 partially inhibited the invasion of B. microti in vitro by 42.0 ± 3.0%, and 48.0 ± 2.1%, respectively. Blood smears revealed that peak infection at 7 days post-infection (dpi) was 19.6%, 24.7%, and 46.7% in the rBMSA1, rBmSA5-1-1, compared to the control groups (healthy mice infected with B. microti only), respectively. Routine blood tests showed higher white blood cell, red blood cell counts, and haemoglobin levels in the 2 groups (BMSA1 and BMSA5 5-1-1) than in the infection control group at 0-28 dpi. Moreover, the 2 groups had higher serum interferon-γ, tumor necrosis factor-α and Interleukin-17A levels, and lower IL-10 levels than the infection control group throughout the study. These 2 potential vaccine candidate proteins partially inhibit in vitro and in vivo B. microti infection and enhance host immunological response against B. microti infection.

How to Detect Antibodies Against Babesia divergens in Human Blood Samples

Background

Today only indirect fluorescent antibody assays (IFAs) are commercially available to detect antibodies against Babesia divergens in humans. IFA is subjective and requires highly experienced staff. We have therefore developed an enzyme-linked immunosorbent assay (ELISA)-based method for measuring anti-B. divergens immunoglobulin G antibodies in human blood samples.

Methods

Crude merozoite extract from in vitro cultures of a new B. divergens isolate was used in ELISA to detect antibodies in different sets of samples: Borrelia burgdorferi-positive samples, healthy individuals, tick-bitten individuals including follow-up samples 3 months later, positive control samples from patients with an active Babesia infection, and samples from malaria-endemic regions. As a reference, IFA was used to detect antibodies in the tick-bitten samples. Western blot was used to evaluate reactions against specific bands in extracts with/without parasites.

Results

Using IFA as the reference method, the sensitivity and specificity of the ELISA were 86% (12/14) and 100% (52/52). There was a very high correlation (r = -0.84; P = .0004) between IFA dilution factors and ELISA absorbances among the samples classified as positive. Five percent of the B. burgdorferi-positive samples were judged as weakly positive and 5% as strongly positive in our ELISA. Western blot showed that the immunodominant antigens (∼120 kDa) were from merozoites and not from erythrocytes.

Conclusions

This ELISA can detect antibodies directed against B. divergens, and it can be a useful and easy assay to handle compared with IFA. The ELISA can also measure high and low levels of antibodies, which could give insight into the recency of a B. divergens infection.

Immune Mediators Important for a Protective Secondary Response to Babesia microti

Babesia microti (B. microti) is a tick-transmitted protozoan parasite that invades red blood cells. It is the primary cause of human babesiosis in the US. The severity of babesiosis caused by B. microti infection can range from asymptomatic to fatal. Risk factors for severe disease include general immune suppression, advanced age (>50) and lack of a spleen. However, severe disease can occur in the absence of any known risk factors. The degree to which tick-transmitted B. microti infection confers protection from subsequent exposure is largely unexplored. This is an important question as both the prevalence and geographic range of tick-transmitted B. microti infection continues to increase and individuals in endemic regions may have multiple exposures over their lifetime. In the current study we used a mouse model to evaluate the degree to which primary infection with B. microti protected against secondary challenge with the same parasite strain. We show that CD4 T cells, and to a lesser extent B cells, contribute to protection. However, mice exhibited significant protection from secondary parasite challenge even in the absence of either CD4 T cells or B cells. The protection mediated by CD4 T cells did not depend on their production of IFN-γ as mice with a targeted gene deletion for the IFN-γ receptor remained fully protected against secondary challenge. Other factors including inducible nitric oxide synthase (iNOS) and the adaptor protein MyD88, important for toll-like receptors, IL-18 and IL-1 signaling, were not important for protection against primary or secondary challenge with B. microti. Thus, our study shows that resolution of primary infection with B. microti results in robust protection against secondary challenge with parasites, at least in the short term. Further studies are needed to evaluate the length of protection and the degree to which protection is impacted by parasite heterogeneity. Although we show an important role for CD4 T cells in protection against secondary challenge, our results suggest that no single aspect of the immune system is solely responsible for adequate protection against secondary challenge with B. microti.

Tafenoquine-Atovaquone Combination Achieves Radical Cure and Confers Sterile Immunity in Experimental Models of Human Babesiosis

Human babesiosis is a potentially fatal tick-borne disease caused by intraerythrocytic Babesia parasites. The emergence of resistance to recommended therapies highlights the need for new and more effective treatments. Here we demonstrate that the 8-aminoquinoline antimalarial drug tafenoquine inhibits the growth of different Babesia species in vitro, is highly effective against Babesia microti and Babesia duncani in mice and protects animals from lethal infection caused by atovaquone-sensitive and -resistant B. duncani strains. We further show that a combination of tafenoquine and atovaquone achieves cure with no recrudescence in both models of human babesiosis. Interestingly, elimination of B. duncani infection in animals following drug treatment also confers immunity to subsequent challenge. Altogether, the data demonstrate superior efficacy of tafenoquine plus atovaquone combination over current therapies for the treatment of human babesiosis and highlight its potential in providing protective immunity against Babesia following parasite clearance.

Histopathological Aspects of the Influence of Babesia microti on the Placentas of Infected Female Rats

Babesiosis is perceived mainly an animal disease; however, awareness that Babesia spp. parasites that can cause diseases in humans is increasing significantly. Babesiosis is spread by the bite of an infected tick (Ixodes spp.), but it can also be transmitted by transfusion of infected blood and from an infected mother to her child during pregnancy or childbirth. The parasites multiply in the bloodstream and destroy red blood cells. This study aimed to assess the influence of Babesia microti on the histological structure of the placenta. Histopathological material collected from pregnant rats infected with Babesia microti was used in the experiment. Microscopic images of the placentas were assessed by Mallory staining and by using methylene blue-stained semi-thin sections. In addition, FISH was used to detect parasite DNA. The presence of piroplasms in both maternal and fetal vessels was demonstrated. Babesia microti infection caused vacuolization of syncytioblasts and cytotrophoblasts, accumulation of collagen fibers in placental villi, and increased adhesion of erythrocytes to the vascular walls. These results indicate that Babesia may influence the course of pregnancy and invite further research on the mechanism of piroplasm penetration into cells.

Parasitic and Fungal Triggers of Cytokine Storm Syndrome

Infections caused by parasites and fungi can trigger the cytokine storm syndrome (CSS). These infections causing CSS can occur together with acquired immunodeficiencies, lymphomas, the use of immunosuppressive medications, transplant recipients, cancer, autoinflammatory, and autoimmune diseases or less frequently in healthy individuals. Histoplasma, Leishmania, Plasmodium, and Toxoplasma are the most frequent organisms associated with a CSS. It is very important to determine a previous travel history when evaluating a patient with a CSS triggered by these organisms as this may be the clue to the causal agent. Even though CSS is treated with specific therapies, an effort to find the causal organism should be carried out since the treatment of the infectious organism may stop the CSS. Diagnosing a CSS in the presence of parasitic or fungal sepsis should also lead to the study of an altered cytotoxic or hemophagocytic response in the susceptible host.

Immune Control in Repeated Babesia microti Infection in a Patient With B-Cell Deficiency

The immunology of human babesiosis is poorly investigated. We present a comprehensive investigation of a 75-year-old man with B-cell deficiency who experienced 3 episodes of babesiosis over a 6-year period. Slowly evolving clinical immunity was observed, as evidenced by milder clinical symptoms and lower peak parasite burden after each subsequent babesiosis episode. The patient exhibited several striking immunologic findings. First, the patient had exceptionally high Babesia microti-specific antibodies despite very few circulating B cells, which predominantly coexpressed CD27 (memory marker) and CD95 (death receptor). Second, we demonstrated the presence of long-lasting NK cells and expansion of T memory stem cells. Third, levels of the IP-10 cytokine directly correlated with parasite burden. These results raise fundamental questions on the priming, maintenance, and location of a B-cell population that produces high antibody levels in the face of severe B-cell deficiency. Our results should invoke interest among researchers to study the immunology and pathogenesis of human babesiosis.

Warm Autoimmune Hemolytic Anemia Secondary to Babesia Microti Infection: A Case Report

Babesia microti is a parasite endemic to the northeastern and midwestern regions of the United States of America and a leading cause of babesiosis. Babesiosis has a non-specific presentation, which can delay diagnosis, leading to increased morbidity and mortality. As the number of reported babesiosis cases increases, there is a need to create more awareness of some atypical presentations that allow for early recognition and treatment. This case report identifies a 75-year-old male with intact spleen who presented with warm autoimmune hemolytic anemia secondary to B. microti and had complete recovery within less than a month after treatment was initiated. We also briefly report on the known and suspected pathophysiology and treatment courses.

Tick-Borne Co-Infections: Challenges in Molecular and Serologic Diagnoses

Co-infections are a poorly understood aspect of tick-borne diseases. In the United States alone, nineteen different tick-borne pathogens have been identified. The majority of these agents are transmitted by only two tick species, Ixodes scapularis and Amblyomma americanum. Surveillance studies have demonstrated the presence of multiple pathogens in individual ticks suggesting a risk of polymicrobial transmission to humans. However, relatively few studies have explored this relationship and its impact on human disease. One of the key factors for this deficiency are the intrinsic limitations associated with molecular and serologic assays employed for the diagnosis of tick-borne diseases. Limitations in the sensitivity, specificity and most importantly, the capacity for inclusion of multiple agents within a single assay represent the primary challenges for the accurate detection of polymicrobial tick-borne infections. This review will focus on outlining these limitations and discuss potential solutions for the enhanced diagnosis of tick-borne co-infections.

Methemoglobinemia Secondary to Babesia Microti Infection: A Novel Case Report

BACKGROUND

Tick-borne illnesses and methemoglobinemia have not been known to occur together in humans. Few cases have been documented in various animals of methemoglobinemia secondary to tick-borne infections.

CASE REPORT

A 49-year-old man with no significant medical history presented to the emergency department from an urgent care with hypoxia saturating in the mid 80s. He also reported a pruritic rash on his back and right shoulder as well as both of his lower extremities. The rash had been present for 4 days. The patient was tachycardic and hypoxic at 90% but denied shortness of breath. He had cyanosis of the lips and fingertips and multiple erythematous, raised, ovoid lesions on the right shoulder and left lower extremity. Methemoglobin levels were elevated at 26%. He was treated with methylene blue, supplemental oxygen, and empiric doxycycline with improvement in his oxygenation. A tick-borne illness panel later tested positive for Babesia microti infection. His skin lesions resolved with the above described treatment. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Both tick-borne illnesses and methemoglobinemia are typically easily treatable with proper antimicrobial coverage and methylene blue, respectively. The current literature is bare regarding concurrent tick-borne illnesses, specifically babesiosis, and methemoglobinemia. Without knowledge and documentation of a potential link between the two conditions, hypoxia, if found to be due to methemoglobinemia, may be treated adequately, but a potentially life-threatening tick-borne illness may continue to cause damage and disease to the patient if not tested for, identified, and treated.

Transfusion-transmitted Babesia spp.: a changing landscape of epidemiology, regulation, and risk mitigation

Babesia spp. are tick-borne parasites with a global distribution and diversity of vertebrate hosts. Over the next several decades, climate change is expected to impact humans, vectors, and vertebrate hosts and change the epidemiology of Babesia. Although humans are dead-end hosts for tick-transmitted Babesia, human-to-human transmission of Babesia spp. from transfusion of red blood cells and whole blood-derived platelet concentrates has been reported. In most patients, transfusion-transmitted Babesia (TTB) results in a moderate-to-severe illness. Currently, in North America, most cases of TTB have been described in the United States. TTB cases outside North America are rare, but case numbers may change over time with increased recognition of babesiosis and as the epidemiology of Babesia is impacted by climate change. Therefore, TTB is a concern of microbiologists working in blood operator settings, as well as in clinical settings where transfusion occurs. Microbiologists play an important role in deploying blood donor screening assays in Babesia endemic regions, identifying changing risks for Babesia in non-endemic areas, investigating recipients of blood products for TTB, and drafting TTB policies and guidelines. In this review, we provide an overview of the clinical presentation and epidemiology of TTB. We identify approaches and technologies to reduce the risk of collecting blood products from Babesia-infected donors and describe how investigations of TTB are undertaken. We also describe how microbiologists in Babesia non-endemic regions can assess for changing risks of TTB and decide when to focus on laboratory-test-based approaches or pathogen reduction to reduce TTB risk.

Protective efficacy and correlates of immunity of immunodominant recombinant Babesia microti antigens

Babesia microti, an intraerythrocytic apicomplexan parasite, is the primary causative agent of human babesiosis and an emerging threat to public health in the United States and elsewhere. An effective vaccine against B. microti would reduce disease severity in acute babesiosis patients and shorten the parasitemic period in asymptomatic individuals, thereby minimizing the risk of transfusion-transmitted babesiosis. Here we report on immunogenicity, protective efficacy, and correlates of immunity following immunization with four immunodominant recombinantly produced B. microti antigens-Serine Reactive Antigen 1 (SERA1), Maltese Cross Form Related Protein 1 (MCFRP1), Piroplasm β-Strand Domain 1 (PiβS1), and Babesia microti Alpha Helical Cell Surface Protein 1 (BAHCS1)-delivered subcutaneously in Montanide ISA 51/CpG adjuvant in three doses to BALB/c mice. Following B. microti parasite challenge, BAHCS1 led to the highest reduction in peak parasitemia (67.8%), followed by SERA1 (44.8%) and MCFRP1 (41.9%); PiβS1 (27.6%) had minimal protective effect. All four B. microti antigens induced high ELISA total IgG and each isotype; however, antibody levels did not directly correlate with anti-parasitic activity in mice. Increased prechallenge levels of some cell populations including follicular helper T cells (TFH) and memory B cells, along with a set of six cytokines [IL-1α, IL-2, IL-3, IL-6, IL-12(p40), and G-CSF] that belong to both innate and adaptive immune responses, were generally associated with protective immunity. Our results indicate that mechanisms driving recombinant B. microti antigen-induced immunity are complex and multifactorial. We think that BAHCS1 warrants further evaluation in preclinical studies.

Infections and Acute Kidney Injury: A Global Perspective

Globally, there are an estimated 13.3 million cases of acute kidney injury (AKI) annually. Although infections are a common cause of AKI globally, most infection-associated AKI occurs in low- and lower-middle-income countries. There are marked differences in the etiology of infection-associated AKI across age groups, populations at risk, and geographic location. This article provides a global overview of different infections that are associated commonly with AKI, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), human immunodeficiency virus, malaria, dengue, leptospirosis, tick-borne illnesses, and viral hemorrhagic fevers. Further discussion focuses on infectious conditions associated with AKI including sepsis, diarrheal diseases and pregnancy, peripartum and neonatal AKI. This article also discusses the future of infection-associated AKI in the framework of climate change. It explores how increased investment in achieving the sustainable development goals may contribute to the International Society of Nephrology's 0 by 25 objective to curtail avoidable AKI-related fatalities by 2025.

Plasma Blood Levels of Tafenoquine following a Single Oral Dosage in BALBc Mice with Acute Babesia microti Infection That Resulted in Rapid Clearance of Microscopically Detectable Parasitemia

Previous studies of mice infected with Babesia microti have shown that a single dose of tafenoquine administered orally is extremely effective at decreasing microscopically detectable parasitemia. However, a critical limitation of studies to date is the lack of data concerning the plasma levels of tafenoquine that are needed to treat babesiosis. In the current study, we begin to address this gap by examining the plasma levels of tafenoquine associated with the rapid reduction of B. microti patent parasitemia in a mouse model of babesiosis. In the current study, we infected BALB/c mice with 1 × 107B. microti-infected red blood cells. Two days post-infection, mice were treated with 20 mg/kg of tafenoquine succinate or vehicle control administered orally by gavage. Parasitemia and plasma levels of tafenoquine were evaluated every 24 h post-treatment for 96 h. This allowed us to correlate blood plasma levels of tafenoquine with reductions in parasitemia in treated mice. Consistent with previous studies, a single oral dose of 20 mg/kg tafenoquine resulted in a rapid reduction in parasitemia. Plasma levels of tafenoquine 24 h post-administration ranged from 347 to 503 ng/mL and declined thereafter. This blood plasma tafenoquine level is similar to that achieved in humans using the current FDA-approved dose for the prevention of malaria.

A conserved protein of Babesia microti elicits partial protection against Babesia and Plasmodium infection

BACKGROUND

The protozoan parasite Babesia microti that causes the zoonotic disease babesiosis resides in the erythrocytes of its mammalian host during its life-cycle. No effective vaccines are currently available to prevent Babesia microti infections.

METHODS

We previously identified a highly seroactive antigen, named Bm8, as a B. microti conserved erythrocyte membrane-associated antigen, by high-throughput protein chip screening. Bioinformatic and phylogenetic analysis showed that this membrane-associated protein is conserved among apicomplexan hemoprotozoa, such as members of genera Babesia, Plasmodium and Theileria. We obtained the recombinant protein Bm8 (rBm8) by prokaryotic expression and purification.

RESULTS

Immunofluorescence assays confirmed that Bm8 and its Plasmodium homolog were principally localized in the cytoplasm of the parasite. rBm8 protein was specifically recognized by the sera of mice infected with B. microti or P. berghei. Also, mice immunized with Bm8 polypeptide had a decreased parasite burden after B. microti or P. berghei infection.

CONCLUSIONS

Passive immunization with Bm8 antisera could protect mice against B. microti or P. berghei infection to a certain extent. These results lead us to hypothesize that the B. microti conserved erythrocyte membrane-associated protein Bm8 could serve as a novel broad-spectrum parasite vaccine candidate since it elicits a protective immune response against Babesiosis and Plasmodium infection.

Anti-parasitic drug discovery against Babesia microti by natural compounds: an extensive computational drug design approach

Tick-borne Babesiosis is a parasitic infection caused by Babesia microti that can infect both animals and humans and may spread by tick, blood transfusions, and organ transplantation. The current therapeutic options for B. microti are limited, and drug resistance is a concern. This study proposes using computational drug design approaches to find and design an effective drug against B. microti. The study investigated the potentiality of nine natural compounds against the pathogenic human B. microti parasite and identified Vasicinone and Evodiamine as the most promising drugs. The ligand structures were optimized using density functional theory, molecular docking, molecular dynamics simulations, quantum mechanics such as HOMO-LUMO, drug-likeness and theoretical absorption, distribution, metabolism, excretion, and toxicity (ADMET), and pharmacokinetics characteristics performed. The results showed that Vasicinone (-8.6 kcal/mol and -7.8 kcal/mol) and Evodiamine (-8.7 kcal/mol and -8.5 kcal/mol) had the highest binding energy and anti-parasitic activity against B. microti lactate dehydrogenase and B. microti lactate dehydrogenase apo form. The strongest binding energy was reported by Vasicinone and Evodiamine; the compounds were evaluated through molecular dynamics simulation at 100 ns, and their stability when they form complexes with the targeted receptors was determined. Finally, the pkCSM web server is employed to predict the ADMET qualities of specific molecules, which can help prevent negative effects that arise from taking the treatment. The SwissADME web server is used to assess the Lipinski rule of five and drug-likeness properties including topological polar surface area and bioavailability. The Lipinski rule is used to estimate significant drug-likeness. The theoretical pharmacokinetics analysis and drug-likeness of the selected compounds are confirmed to be accepted by the Lipinski rule and have better ADMET features. Thus, to confirm their experimental value, these mentioned molecules should be suggested to carry out in wet lab, pre-clinical, and clinical levels.

Case report: First report on human infection by tick-borne Babesia bigemina in the Amazon region of Ecuador

Babesiosis is a protozoan disease acquired by the bite of different species of ticks. More than 100 Babesia spp. infect wild and domestic animals worldwide, but only a few have been documented to infect humans. Generally, babesiosis is asymptomatic in immunocompetent persons; however, in immunocompromised can be life-threatening. A 13-year-old boy from the Amazon region presented with a 3-month evolution of fever, chills, general malaise, and arthralgia accompanied by anemia and jaundice. In the last 4 years was diagnosed with chronic kidney failure. By nested-PCR using 18S RNA ribosomal gene as target and DNA sequencing, the phylogenetic analysis showed Babesia bigemina as the causative agent in the blood. Treatment with oral quinine plus clindamycin for six continuous weeks was effective with no relapse occurring during 12 months of follow-up. This is the second human case in Ecuador but the first caused by the zoonotic B. bigemina which confirms the existence of active transmission that should alert public health decision-making authorities on the emergence of this zoonosis and the need for research to determine strategies to reduce tick exposure.

Clinical applications of gene therapy for rare diseases: A review

Rare diseases collectively exact a high toll on society due to their sheer number and overall prevalence. Their heterogeneity, diversity, and nature pose daunting clinical challenges for both management and treatment. In this review, we discuss recent advances in clinical applications of gene therapy for rare diseases, focusing on a variety of viral and non-viral strategies. The use of adeno-associated virus (AAV) vectors is discussed in the context of Luxturna, licenced for the treatment of RPE65 deficiency in the retinal epithelium. Imlygic, a herpes virus vector licenced for the treatment of refractory metastatic melanoma, will be an example of oncolytic vectors developed against rare cancers. Yescarta and Kymriah will showcase the use of retrovirus and lentivirus vectors in the autologous ex vivo production of chimeric antigen receptor T cells (CAR-T), licenced for the treatment of refractory leukaemias and lymphomas. Similar retroviral and lentiviral technology can be applied to autologous haematopoietic stem cells, exemplified by Strimvelis and Zynteglo, licenced treatments for adenosine deaminase-severe combined immunodeficiency (ADA-SCID) and β-thalassaemia respectively. Antisense oligonucleotide technologies will be highlighted through Onpattro and Tegsedi, RNA interference drugs licenced for familial transthyretin (TTR) amyloidosis, and Spinraza, a splice-switching treatment for spinal muscular atrophy (SMA). An initial comparison of the effectiveness of AAV and oligonucleotide therapies in SMA is possible with Zolgensma, an AAV serotype 9 vector, and Spinraza. Through these examples of marketed gene therapies and gene cell therapies, we will discuss the expanding applications of such novel technologies to previously intractable rare diseases.

Successful treatment with doxycycline monotherapy for human infection with Babesia venatorum (Babesiidae, Sporozoa) in China: a case report and proposal for a clinical regimen

BACKGROUND

Human babesiosis is a worldwide disease caused by intraerythrocytic protozoa of the genus Babesia. It is transmitted by bites from ixodid ticks, and mechanically transmitted by blood transfusion. It is primarily treated with quinine and/or atovaquone, which are not readily available in China. In this study, we developed a novel treatment regimen involving doxycycline monotherapy in a patient with severe Babesia venatorum infection as an alternative therapeutic medication. The aim of our study is to provide a guidance for clinical practice treatment of human babesiosis.

CASE PRESENTATION

A 73-year-old man who had undergone splenectomy and blood transfusion 8 years prior, presented with an unexplained fever, headache, and thrombocytopenia, and was admitted to the Fifth Medical Center of the PLA General Hospital. He was diagnosed with B. venatorum infection by morphological review of thin peripheral blood smears, which was confirmed by multi-gene polymerase chain reaction (PCR), and sequencing of the entire 18s rRNA and partial β-tubulin encoding genes, as well as isolation by animal inoculation. The doxycycline monotherapy regimen (peros, 0.1 g bisindie) was administered following pharmacological guidance and an effective outcome was observed. The patient recovered rapidly following the doxycycline monotherapy. The protozoan load in peripheral blood samples decreased by 88% in hematocrit counts after 8 days, and negative PCR results were obtained after 90 days of follow-up at the hospital. The treatment lasted for 3 months without any side effects or sequelae. The nine-month follow-up survey of the patient did not reveal any signs of recrudescence or anti-babesial tolerance.

CONCLUSIONS

We have reported a clinical case of successful doxycycline monotherapy for human babesiosis caused by B. venatorum, which provides an optional medical intervention for human babesiosis.

Transfusion-Transmitted Disorders 2023 with Special Attention to Bone Marrow Transplant Patients

Transfusion medicine is traditionally a strong/fundamental part of clinical practice, saving hundreds of millions of lives. However, blood-borne or transmitted infections are a well-known and feared possibility, a risk we relentlessly mitigate. Pathogens are continuously and rather quickly changing, so during the last decade, many, sometimes exotic, new pathogens and diseases were recorded and analyzed, and some of them were proved to be transmitted with transfusions. Blood or blood component transfusions are carried out after cautious preparative screening and inactivation maneuvers, but in some instances, newly recognized agents might escape from standard screening and inactivation procedures. Here, we try to focus on some of these proven or potentially pathogenic transfusion-transmitted agents, especially in immunocompromised patients or bone marrow transplantation settings. These pathogens are sometimes new challenges for preparative procedures, and there is a need for more recent, occasionally advanced, screening and inactivation methods to recognize and eliminate the threat a new or well-known pathogen can pose. Pathogen transmission is probably even more critical in hemophiliacs or bone marrow transplant recipients, who receive plasma-derived factor preparations or blood component transfusions regularly and in large quantities, sometimes in severely immunosuppressed conditions. Moreover, it may not be emphasized enough that transfusions and plasma-derived product administrations are essential to medical care. Therefore, blood-borne transmission needs continued alertness and efforts to attain optimal benefits with minimized hazards.

Comparative chemical genomics in Babesia species identifies the alkaline phosphatase phoD as a novel determinant of resistance

Babesiosis is an emerging zoonosis and widely distributed veterinary infection caused by 100+ species of Babesia parasites. The diversity of Babesia parasites, coupled with the lack of potent inhibitors necessitates the discovery of novel conserved druggable targets for the generation of broadly effective antibabesials. Here, we describe a comparative chemogenomics (CCG) pipeline for the identification of novel and conserved targets. CCG relies on parallel in vitro evolution of resistance in independent populations of evolutionarily-related Babesia spp. ( B. bovis and B. divergens ). We identified a potent antibabesial inhibitor from the Malaria Box, MMV019266. We were able to select for resistance to this compound in two species of Babesia, achieving 10-fold or greater resistance after ten weeks of intermittent selection. After sequencing of multiple independently derived lines in the two species, we identified mutations in a single conserved gene in both species: a membrane-bound metallodependent phosphatase (putatively named PhoD). In both species, the mutations were found in the phoD-like phosphatase domain, proximal to the predicted ligand binding site. Using reverse genetics, we validated that mutations in PhoD confer resistance to MMV019266. We have also demonstrated that PhoD localizes to the endomembrane system and partially with the apicoplast. Finally, conditional knockdown and constitutive overexpression of PhoD alter the sensitivity to MMV019266 in the parasite: overexpression of PhoD results in increased sensitivity to the compound, while knockdown increases resistance, suggesting PhoD is a resistance mechanism. Together, we have generated a robust pipeline for identification of resistance loci, and identified PhoD as a novel determinant of resistance in Babesia species.

Highlights

Use of two species for in vitro evolution identifies a high confidence locus associated with resistance Resistance mutation in phoD was validated using reverse genetics in B. divergens Perturbation of phoD using function genetics results in changes in the level of resistance to MMV019266Epitope tagging reveals localization to the ER/apicoplast, a conserved localization with a similar protein in diatoms Together, phoD is a novel resistance determinant in multiple Babesia spp .

Why is Babesia not killed by artemisinin like Plasmodium?

Babesia spp. are intraerythrocytic apicomplexans that digest and utilize red blood cells in a similar way to intraerythrocytic Plasmodium spp., but unlike the latter, are not sensitive to artemisinin. A comparison of Babesia and Plasmodium genomes revealed that Babesia genomes, which are smaller than those of Plasmodium, lack numerous genes, and especially haem synthesis-related genes, that are found in the latter. Single-cell sequencing analysis showed that the different treatment groups of Babesia microti with expressed pentose phosphate pathway-related, DNA replication-related, antioxidation-related, glycolysis-related, and glutathione-related genes were not as sensitive to artemether as Plasmodium yoelii 17XNL. In particular, pentose phosphate pathway-related, DNA replication-related, and glutathione-related genes, which were actively expressed in P. yoelii 17XNL, were not actively expressed in B. microti. Supplying iron in vivo can promote the reproduction of B. microti. These results suggest that Babesia spp. lack a similar mechanism to that of malaria parasites through which the haem or iron in hemoglobin is utilized, and that this likely leads to their insensitivity to artemisinin.

Neurologic Complications of Babesiosis, United States, 2011-2021

Babesiosis is a globally distributed parasitic infection caused by intraerythrocytic protozoa. The full spectrum of neurologic symptoms, the underlying neuropathophysiology, and neurologic risk factors are poorly understood. Our study sought to describe the type and frequency of neurologic complications of babesiosis in a group of hospitalized patients and assess risk factors that might predispose patients to neurologic complications. We reviewed medical records of adult patients who were admitted to Yale-New Haven Hospital, New Haven, Connecticut, USA, during January 2011-October 2021 with laboratory-confirmed babesiosis. More than half of the 163 patients experienced >1 neurologic symptoms during their hospital admissions. The most frequent symptoms were headache, confusion/delirium, and impaired consciousness. Neurologic symptoms were associated with high-grade parasitemia, renal failure, and history of diabetes mellitus. Clinicians working in endemic areas should recognize the range of symptoms associated with babesiosis, including neurologic.

Deployment of a Reservoir-Targeted Vaccine Against Borrelia burgdorferi Reduces the Prevalence of Babesia microti Coinfection in Ixodes scapularis Ticks

In the Northeast and upper Midwest of the United States, Babesia microti and Borrelia burgdorferi use Ixodes scapularis ticks as vector and Peromyscus leucopus mice as major reservoir host. We previously established, in a 5-year field trial, that a reservoir-targeted outer surface protein A vaccine reduces the prevalence of B. burgdorferi-infected ticks. We accessed ticks and mouse blood samples collected during the trial, extracted total DNA, and amplified the B. microti 18S rRNA gene. Vaccine deployment reduced the prevalence of ticks coinfected with B. microti and that of mice infected with B. microti. Breaking the enzootic cycle of B. burgdorferi may reduce the incidence of babesiosis.

Dielectric characterization of Babesia bovis using the dielectrophoretic crossover frequency

Coinfection with the tick-transmitted pathogen Babesia spp. is becoming a serious health problem because of the erythrocyte invasion through Ixodes scapularis tick. The transmission of this protozoan by blood transfusion often results in high morbidity and mortality in recipients. A novel way to detect parasitized erythrocytes is by utilizing dielectrophoresis, an electrokinetic technique on a microfluidic platform, to improve the diagnostics of Babesia spp. The differences in the dielectric properties of Babesia spp.-infected erythrocytes versus healthy erythrocytes were exploited to design a fast and cost-effective diagnostic tool. One crucial factor for a successful diagnostic platform via dielectrophoretic separation is the dielectric characterization of Babesia-infected erythrocytes, which is investigated in this paper. The influence of medium conductivity and erythrocytes phenotype and genotype over the first crossover frequency (f_co1 ) are used to quantify the dielectric properties of the infected cells. A sigmoidal curve was plotted via curve fitting of the single-shell model, which has been proven appropriate for parasitized cell populations where considerable cell geometry variation occurs. The difference in these curves is relevant for the separation of cells population. Microliters of sample and reagent were used throughout this experiment; the scale, results obtained, and simplicity of the system often make it very suitable for point-of-care babesiosis disease diagnostics.

Babesiosis: An Atypical Cause of Respiratory Failure

Babesiosis is a parasitic infection of the Babesia protozoa, which has been increasing in incidence in endemic areas of the United States. Symptoms of babesiosis can occur on a wide spectrum, from a mild flu-like illness to a fulminant disease course. Known complications of severe cases include intravascular hemolytic anemia and may involve the coagulation system, heart, spleen, kidneys, and in some cases, the lungs. This case report describes an 81-year-old, asplenic female in northern Wisconsin who presented to a hospital with shortness of breath and a non-productive cough. Definitive diagnosis of babesiosis, which was made through both a nucleic acid panel and blood smear, was initially delayed given the rare pulmonary manifestation of babesiosis. When the lungs are involved in the disease course, non-cardiogenic pulmonary edema leading to acute respiratory distress syndrome is among the most commonly seen complications. The pathophysiology of pulmonary involvement has not been made entirely clear but is most likely multifactorial, including the sequelae of changes to both the patient's red blood cells and pulmonary vasculature. This report highlights that atypical tick-borne illnesses like babesiosis should be considered as a cause of acute respiratory failure, particularly in the setting of sepsis and fever. The threshold for parasitic testing should be low in patients in endemic regions with risk factors, including increased age and history of asplenia, as babesiosis frequently has no localizing symptoms to suggest a protozoan infection. As babesiosis incidence continues to rise, prompt diagnosis and proper treatment can prevent severe complications and death in patients.

Human Borrelia miyamotoi Infection in North America

Borrelia miyamotoi is an emerging pathogen that causes a febrile illness and is transmitted by the same hard-bodied (ixodid) ticks that transmit several other pathogens, including Borrelia species that cause Lyme disease. B. miyamotoi was discovered in 1994 in Ixodes persulcatus ticks in Japan. It was first reported in humans in 2011 in Russia. It has subsequently been reported in North America, Europe, and Asia. B. miyamotoi infection is widespread in Ixodes ticks in the northeastern, northern Midwestern, and far western United States and in Canada. In endemic areas, human B. miyamotoi seroprevalence averages from 1 to 3% of the population, compared with 15 to 20% for B. burgdorferi. The most common clinical manifestations of B. miyamotoi infection are fever, fatigue, headache, chills, myalgia, arthralgia, and nausea. Complications include relapsing fever and rarely, meningoencephalitis. Because clinical manifestations are nonspecific, diagnosis requires laboratory confirmation by PCR or blood smear examination. Antibiotics are effective in clearing infection and are the same as those used for Lyme disease, including doxycycline, tetracycline, erythromycin, penicillin, and ceftriaxone. Preventive measures include avoiding areas where B. miyamotoi-infected ticks are found, landscape management, and personal protective strategies such as protective clothing, use of acaricides, and tick checks with rapid removal of embedded ticks.

Transfusion-transmitted babesiosis in a patient with sickle cell disease undergoing chronic red cell exchange

BACKGROUND

Prior to laboratory-based blood donor screening for Babesia, transfusion-transmitted babesiosis (TTB) was a leading infectious risk to the blood supply in the United States.

CASE REPORT

A 30-year-old man with sickle cell disease (SCD) who had been on a chronic automated red cell exchange (RCE) regimen since childhood, presented approximately 2 months after an RCE, with fever, neck pain, and photophobia. Meningitis was excluded, and he was discharged. He presented again 2 days later with persistent fever, chills, headache, fatigue, and loss of appetite.

RESULTS

On examination, the patient was febrile but hemodynamically stable. Intra-erythrocytic inclusions were identified on a peripheral blood smear (<0.5%). B. microti IgM and IgG titers were >1:320 (Reference <1:20) >1:1024 (Reference <1:64), respectively. B. microti was confirmed by nucleic acid testing. The patient lived in a Babesia endemic state but had no risk factors for tick-borne acquisition. Of the 65 units he received in the preceding 6 months, 58 had been screened for Babesia. One of the donors of the 7 untested units was B. microti seropositive (titer 1:128; Reference 1: 64). The donor was asymptomatic and resided in a state in which Babesia screening was not required. He reported traveling in the year before his donation.

CONCLUSION

Although rare, TTB is still possible despite regional screening, underscoring the need for provider vigilance and education, especially in non-endemic areas. Patients with SCD are particularly vulnerable given their high frequency of transfusion and complex needs requiring blood procurement from states where Babesia screening is not mandatory.

Prevalence of Babesia and Ehrlichia in owned dogs with suspected tick-borne infection in Hong Kong, and risk factors associated with Babesia gibsoni

Babesiosis and ehrlichiosis are the most clinically significant tick-borne infections in dogs. Although epidemiological investigations of these diseases have been performed in some Asian regions, little data is available in Hong Kong, where competent vector tick species are endemic. The objectives of this study were to determine the molecular prevalence of Ehrlichia canis and Babesia species (B. canis, B. gibsoni, B. vogeli) in owned dogs suspected of tick-borne infection in Hong Kong and to identify risk factors associated with B. gibsoni infection. Electronic records from the Veterinary Diagnostic Laboratory of City University of Hong Kong were searched to identify canine blood samples submitted for molecular testing of these pathogens by real time PCR between March 2018 and May 2021. Electronic patient records from the affiliated veterinary hospital were searched to identify a subset of tested dogs to investigate the potential risk factors for B. gibsoni infection using logistic regression models. Among 1508 tested dogs for all four pathogens of interest, Babesia spp. were detected in 435 (28.8%) and E. canis in 112 (7.4%). Babesia gibsoni was detected in 408 dogs while B. vogeli was detected in 27 dogs. Babesia canis was not detected in any dog. Co-infections of different combinations of B. gibsoni, B. vogeli and E. canis were present in 25 dogs. In multivariable logistic regression, mixed breed dogs were more likely to be infected with B. gibsoni than purebreds (P = 0.005), while dogs > 10 years of age were less likely to be infected than younger dogs (P = 0.019). Hematological abnormalities significantly associated with B. gibsoni infection included thrombocytopenia, neutropenia, or pancytopenia. Babesiosis caused by B. gibsoni is a common infection in owned dogs suspected of tick-borne infection in Hong Kong. The risk factors reported should be considered in diagnosing dogs suspected of infection with this agent. Furthermore, consideration for testing for B. gibsoni infection should be given if the results of a complete blood count show thrombocytopenia even in the absence of anemia, neutropenia or pancytopenia.

Cardiac Complications of Human Babesiosis

BACKGROUND

Human babesiosis is a worldwide emerging tick-borne disease caused by intraerythrocytic protozoa. Most patients experience mild to moderate illness, but life-threatening complications can occur. Although cardiac complications are common, the full spectrum of cardiac disease and the frequency, risk factors, and outcomes in patients experiencing cardiac complications are unclear. Accordingly, we carried out a record review of cardiac complications among patients with babesiosis admitted to Yale-New Haven Hospital over the last decade to better characterize cardiac complications of babesiosis.

METHODS

We reviewed the medical records of all adult patients with babesiosis admitted to Yale-New Haven Hospital from January 2011 to October 2021, confirmed by identification of Babesia parasites on thin blood smear and/or by polymerase chain reaction. The presence of Lyme disease and other tick-borne disease coinfections were recorded.

RESULTS

Of 163 enrolled patients, 32 (19.6%) had ≥1 cardiac complication during hospitalization. The most common cardiac complications were atrial fibrillation (9.4%), heart failure (8.6%), corrected QT interval prolongation (8.0%), and cardiac ischemia (6.8%). Neither cardiovascular disease risk factors nor preexisting cardiac conditions were significantly associated with the development of cardiac complications. The cardiac complication group had a greater prevalence of high-grade parasitemia (>10%) (P < .001), longer median length of both hospital (P < .001) and intensive care unit stay (P < .001), and a higher mortality rate (P = .02) than the group without cardiac complications.

CONCLUSIONS

Cardiac complications of acute babesiosis are common and occurred in approximately one-fifth of this inpatient sample. Further investigation is needed to elucidate the relationship between babesiosis severity and cardiac outcomes.

Serum metabolomic profiles in BALB/c mice induced by Babesia microti infection

Introduction

The protozoan parasite Babesia microti is the primary cause of human babesiosis. This parasite invades and multiplies inside red blood cells (RBCs), and infections differ significantly based on the age and immune competency of the host. The aim of this study was to investigate the use of serum metabolic profiling to identify systemic metabolic variations between B. microti-infected mice and noninfected controls.

Methods

A serum metabolomics analysis of BALB/c mice that had been intraperitoneally injected with 10⁷ B. microti-infected RBCs was performed. Serum samples from the early infected group (2 days postinfection), the acutely infected group (9 days postinfection), and the noninfected group were collected and evaluated using a liquid chromatography-mass spectrometry (LC-MS) platform. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and orthogonal partial least squares discriminant analysis (OPLS-DA) identified metabolomic profiles that differentiated the B. microti-infected and noninfected groups.

Results

Our results confirm that the serum metabolome is significantly influenced by acute B. microti infection and show that infection results in dysregulation of metabolic pathways and perturbation of metabolites. Acutely infected mice displayed perturbations in metabolites associated with taurine and hypotaurine metabolism, histidine metabolism, and arachidonic acid metabolism. Taurocholic acid, anserine, and arachidonic acid may be potential candidates as serological biomarkers for diagnosing B. microti infection at the acute stage. These metabolites could be further examined for their role in disease complexity.

Discussion

Our findings demonstrate that the acute stage of B. microti infection induces abnormalities in the metabolites present in mouse serum and provide new insight into the mechanisms involved in systemic metabolic changes that occur during B. microti infection.

The impact of ABO and RhD blood types on Babesia microti infection

BACKGROUND

Babesiosis is an emerging infectious disease caused by intraerythrocytic Babesia parasites that can cause severe disease and death. While blood type is known to affect the mortality of Plasmodium falciparum malaria patients, associations between red blood cell (RBC) antigens and Babesia microti infection and disease severity are lacking.

METHODS

We evaluated RhD and ABO blood types of Babesia-infected (18S rRNA reactive) blood donors in 10 endemic states in the Northeastern and northern Midwestern United States. We also assessed possible associations between RhD and ABO blood types and disease severity among hospitalized babesiosis patients in Connecticut.

RESULTS

A total of 768 Babesia-infected blood donors were analyzed, of which 750 (97.7%) had detectable B. microti-specific antibodies. B. microti-infected blood donors were more likely to be RhD- (OR of 1.22, p-value 0.024) than RhD+ donors. Hospitalized RhD- babesiosis patients were more likely than RhD+ patients to have high peak parasitemia (p-value 0.017), which is a marker for disease severity. No differences in RhD+ blood type were noted between residents of the Northeast (OR of 0.82, p-value 0.033) and the Midwest (OR of 0.74, p-value 0.23). Overall, ABO blood type was not associated with blood donor B. microti infection, however, B. microti-infected donors in Maine and New Jersey were more likely to be blood type B compared to non-type B (OR 2.49 [p = 0.008] and 2.07 [p = 0.009], respectively), while infected donors from Pennsylvania were less likely to be type B compared to non-type B (OR 0.32 [p = 0.02]).

CONCLUSIONS

People expressing RhD antigen may have a decreased risk of B. microti infection and babesiosis severity. The association of B antigen with B. microti infection is less clear because the antigen appeared to be less prevalent in infected Pennsylvania blood donors but more prevalent in Maine and New Jersey infected donors. Future studies should quantify associations between B. microti genotypes, RBC antigens, and the frequency and severity of B. microti infection to increase our understanding of human Babesia pathogenesis and improve antibody, vaccine, and RBC exchange transfusion strategies.

Animal models of the immunology and pathogenesis of human babesiosis

Animal models of human babesiosis have provided a basic understanding of the immunological mechanisms that clear, or occasionally exacerbate, Babesia infection and those pathological processes that cause disease complications. Human Babesia infection can cause asymptomatic infection, mild to moderate disease, or severe disease resulting in organ dysfunction and death. More than 100 Babesia species infect a wide array of wild and domestic animals, and many of the immunologic and pathologic responses to Babesia infection are similar in animals and humans. In this review, we summarize the knowledge gained from animal studies, their limitations, and how animal models or alternative approaches can be further leveraged to improve our understanding of human babesiosis.

Molecular detection of Babesia microti in dromedary camels in Egypt

Babesia microti (Apicomplexa: Piroplasmida) causes a medically important tick-borne zoonotic protozoan disease. Egyptian camels are susceptible to Babesia infection; however, just a few cases have been documented. This study aimed to identify Babesia species, specifically Babesia microti, and their genetic diversity in dromedary camels in Egypt and associated hard ticks. Blood and hard tick samples were taken from 133 infested dromedary camels slaughtered in Cairo and Giza abattoirs. The study was conducted from February to November 2021. The 18S rRNA gene was amplified by polymerase chain reaction (PCR) to identify Babesia species. Nested PCR targeting the β-tubulin gene was used to identify B. microti. The PCR results were confirmed by DNA sequencing. Phylogenetic analysis based on the ß-tubulin gene was used to detect and genotype B. microti. Three tick genera were identified in infested camels (Hyalomma, Rhipicephalus, and Amblyomma). Babesia species were detected in 3 out of 133 blood samples (2.3%), while Babesia spp. were not detected in hard ticks by using the 18S rRNA gene. B. microti was identified in 9 out of 133 blood samples (6.8%) and isolated from Rhipicephalus annulatus and Amblyomma cohaerens by the β-tubulin gene. The phylogenetic analysis of the β-tubulin gene revealed that USA-type B. microti was prevalent in Egyptian camels. The results of this study suggested that the Egyptian camels may be infected with Babesia spp. and the zoonotic B. microti strains, which pose a potential risk to public health.

The Infection Rate of Bird-Feeding Ixodes ricinus Ticks with Borrelia garinii and B. valaisiana Varies with Host Haemosporidian Infection Status

BACKGROUND

Birds are known to maintain and spread human pathogenic borreliae, but they are common hosts of diverse parasite communities, notably haemosporidians. Only a few studies examined whether tick infestation and/or Borrelia prevalences vary with hosts' haemosporidian infection status.

METHODS

Here, we study whether Ixodes ricinus infestation rates and Borrelia infection rates in bird-feeding ticks vary according to haemosporidian infection status in a community of free-living avian tick hosts.

RESULTS

Birds of six avian species harbored the majority of ticks. Both the tick infestation prevalence and the intensity peaked during spring and summer, but while bird-feeding nymphs prevailed in spring, bird-feeding larvae dominated in summer. Almost half of the bird-feeding ticks were found to be positive for B. burgdorferi s.l. Although the majority of infections involved bird-associated B. garinii and B. valaisiana, B. garinii appears to be the dominant Borrelia strain circulating in locally breeding avian species. We detected a negative link between the hosts' haemosporidian infection status and the Borrelia infection rate of bird-feeding ticks, but the association was dependent on the host's age.

CONCLUSIONS

Our results on tick infestation intensity support the idea that more immunologically vulnerable hosts harbor more ticks but suggest that different mechanisms may be responsible for tick infestation rates among immunologically naïve and experienced avian hosts. The results on Borrelia infection rates in bird-feeding ticks are consistent with studies revealing that intracellular parasites, such as haemosporidians, can benefit from the host immune system prioritizing immune responses against extracellular parasites at the expense of immune responses against intracellular parasites. The findings of our study urge for a more robust design of parasitological studies to understand the ecology of interactions among hosts and their parasites.

Prevalence and phylogenetic analysis of Babesia parasites in reservoir host species in Fujian province, Southeast China

Babesiosis is a tick-borne disease that mainly affects small mammals and has been reported in at least five provinces in China. However, the host range and geographical distribution of the parasite in Fujian province are unclear. Therefore, we investigated the prevalence and genetic characteristics of Babesia in Fujian province, Southeast China, between 2015 and 2020. Rodent blood samples were collected from 26 different surveillance sites across Fujian province. Genomic DNA was extracted to screen for Babesia infection using polymerase chain reaction based on 18S rRNA. DNA samples from 316 domestic goats, 85 water buffalo, 56 domestic dogs and 18 domestic pigs were examined. The prevalence of Babesia was statistically analysed using the Chi-square test or Fisher's exact test. Babesia infections were detected in 3.96% (43/1,087; 95%CI: 2.80%, 5.12%) of rodents and 1.26% (6/475; 95%CI: 0.26%, 2.26%) of other mammals. Multivariate logistic regression analysis revealed that irrigated cropland, shrubs and forests were risk factors for Babesia microti infections. The infection rates among domestic pigs, dogs and goats were 5.56%, 1.79% and 1.27%, respectively, with no infection found in water buffalo. The 18S rRNA gene sequencing revealed that rodents were infected with Babesia (sensu lato), whereas other mammals were infected with Babesia (sensu stricto). The geographical distribution and phylogenetic relationship of Babesia was determined in Southeast China. Mammals, particularly wild rodents, maybe the main natural hosts of Babesia in Fujian. Our findings provide a foundation for public health officials to develop prevention and control measures for Babesia.