Cases of transfusion‐transmitted babesiosis occurring in nonendemic areas: a diagnostic dilemma

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.

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 .

Malignant human thyroid neoplasms associated with blood parasitic (haemosporidian) infection

Investigation of archival cytological material obtained by cytologists during fine-needle aspiration biopsy in follicular, papillary, and medullary human thyroid cancers revealed haemosporidian (blood parasitic) infection. Haemosporidian infection was detected as exo- and intraerythrocytic stages of development in thyrocytes schizogony. The exoerythrocytic stage of development is represented as microschizonts in a thyroid needle biopsy specimen. Probably, blood parasitic infection is the common etiology for these pathologies. All biopsy material in medical laboratories was stained with RomanowskyGiemsa stain. To clarify the localization of nuclei (DNA) of thyrocytes and nuclei (DNA) of haemosporidian infection in cytological material following investigation of the entire set of smears, a selective series of original archival smears was stained (restained) with a Feulgen/Schiff reagent. Staining of smears with RomanowskyGiemsa stain is an adsorption method that enables re-use of the same smears for staining with a Feulgen/Schiff reagent where the fuchsin dye, after DNA hydrolysis by hydrochloric acid, is incorporated into DNA and stains it in redviolet (crimsonlilac) color. An intentionally unstained protoplasm of blood parasitic infection was present as a light band around erythrocyte nuclei. In follicular thyroid cancer, Feulgen staining of thyrocytes revealed nuclear DNA and parasitic DNA (haemosporidium nuclei) as point inclusions and rings and diffusely distributed in the thyrocyte cytoplasm. The thyrocyte cytoplasm and nuclei were vacuolated, with thyrocyte nuclei being deformed, flattened, and displaced to the cell periphery. The erythrocytes, which were initially stained with eosin (orange color), contained haemosporidian nuclei (DNA). In some cases, endoglobular inclusions in thyrocytes and erythrocytes were of the same size. In papillary thyroid cancer, we were able to localize the nuclear DNA of thyrocytes and the parasitic DNA as point inclusions and diffusely distributed in the thyrocyte cytoplasm. Two or more polymorphic nuclei may eccentrically occur in the hyperplastic cytoplasm. Haemosporidian microschizonts occurred circumnuclearly in thyrocytes and as an exoerythrocytic stage in the blood. The erythrocyte cytoplasm contained redviolet polymorphic haemosporidian nuclei (DNA). In medullary thyroid cancer, the hyperplastic cytoplasm of thyrocytes contained eccentrically located nuclei (DNA) of thyrocytes and small haemosporidian nuclei (DNA), which may occupy the whole thyrocyte. There were thyrocytes with vacuolated cytoplasm and pronounced nuclear polymorphism. The size of hyperplastic nuclei was several times larger than that of normal thyrocyte nuclei. The color of stained cytoplasmic and nuclear vacuoles of thyrocytes was less redviolet compared with that of surrounding tissues, which probably indicates the presence of parasitic DNA in them. The haemosporidian nuclear material in erythrocytes is represented by polymorphic nuclei, which may indicate the simultaneous presence of different pathogen species and/or generations in the blood. Intracellular parasitism of haemosporidian infection in thyrocytes (schizogony) associated with three thyroid cancers leads to pronounced cytoplasmic hyperplasia, cytoplasmic vacuolization, and nuclear vacuolization of the thyrocyte, followed by impaired secretory function. Multinucleated thyrocytes with incomplete cytokinesis appear. The absence of lytic death of the affected thyrocytes indicates that the contagium is able to control apoptosis and influence physiological functions of the cell. There is deformation of the nuclei, which leads to a decrease in their size, their flattening and displacement to the cell periphery, with high risk of DNA mutations and deletions in affected cells, reaching a neoplastic level.

Do Not Forget About the Ticks: An Unusual Cause of Fever, GI Distress, and Cytopenias in a Child With ALL

We report the case of a 5-year-old male with B-cell acute lymphoblastic leukemia in remission, receiving maintenance chemotherapy, who presented with fever, emesis, diarrhea, headache, and lethargy. He developed rapidly progressive cytopenias and was found to have acute human granulocytic anaplasmosis as well as evidence of past infection with Babesia microti. The case highlights the need to maintain a broad differential for infection in children undergoing chemotherapy or other immunosuppressive therapies with possible or known tick exposure.

Transfusion transmitted babesiosis: A systematic review of reported cases

BACKGROUND

Transfusion transmitted babesiosis (TTB) has a high mortality rate but may go unrecognized, particularly in non-endemic areas. We therefore conducted a systematic review to better characterize clinical aspects of TTB.

METHODS

A literature search was conducted in PubMed and CINAHL databases, from which 25 eligible articles describing 60 TTB patients met criteria for data extraction.

RESULTS

Symptom evaluation was provided for 25 implicated donors: 18/25 (72%) were asymptomatic while 7/25 (28%) had mild flu-like symptoms but were asymptomatic at time of donation. It was common for a single donor or donation to infect multiple patients. Where reported, species included B. microti - 54/60 (90%), B. duncani - 3/60 (5%), and B. divergens-like/MO-1 - 1/60 (2%). Most TTB patients (44/60, 73%) resided in endemic states, while most TTB deaths 6/9 (67%) occurred in non-endemic states. Severity of hemolysis was proportional to degree of parasitemia. Mortality in our series was 9/60 (15%); most deaths occurred at extremes of the age spectrum: 6/9 non-survivors were aged >55 years, 2/9 were <1 year, only 1/9 was 2-54 years. Number of comorbidities was higher among non-survivors (median = 4) compared to survivors (median = 1).

CONCLUSIONS

All implicated donors (for which symptoms data were reported) resulting in TTB infections were asymptomatic at the time of donation, and it was common for a single donor or donation to infect multiple patients. Mortality of TTB appeared highest among those with more comorbidities and in non-endemic states. Heightened awareness of this diagnosis is key in its recognition.

Detection and Transstadial Passage of Babesia Species and Borrelia burgdorferi Sensu Lato in Ticks Collected from Avian and Mammalian Hosts in Canada

Lyme disease and human babesiosis are the most common tick-borne zoonoses in the Temperate Zone of North America. The number of infected patients has continued to rise globally, and these zoonoses pose a major healthcare threat. This tick-host-pathogen study was conducted to test for infectious microbes associated with Lyme disease and human babesiosis in Canada. Using the flagellin (flaB) gene, three members of the Borrelia burgdorferi sensu lato (Bbsl) complex were detected, namely a Borrelia lanei-like spirochete, Borrelia burgdorferi sensu stricto (Bbss), and a distinct strain that may represent a separate Bbsl genospecies. This novel Bbsl strain was detected in a mouse tick, Ixodes muris, collected from a House Wren, Troglodytes aedon, in Quebec during the southward fall migration. The presence of Bbsl in bird-feeding larvae of I. muris suggests reservoir competency in three passerines (i.e., Common Yellowthroat, House Wren, Magnolia Warbler). Based on the 18S ribosomal RNA (rRNA) gene, three Babesia species (i.e., Babesia divergens-like, Babesia microti, Babesia odocoilei) were detected in field-collected ticks. Not only was B. odocoilei found in songbird-derived ticks, this piroplasm was apparent in adult questing blacklegged ticks, Ixodes scapularis, in southern Canada. By allowing live, engorged ticks to molt, we confirm the transstadial passage of Bbsl in I. muris and B. odocoilei in I. scapularis. Bbss and Babesia microti were detected concurrently in a groundhog tick, Ixodes cookei, in Western Ontario. In Alberta, a winter tick, Dermacentor albipictus, which was collected from a moose, Alces alces, tested positive for Bbss. Notably, a B. divergens-like piroplasm was detected in a rabbit tick, Haemaphysalis leporispalustris, collected from an eastern cottontail in southern Manitoba; this Babesia species is a first-time discovery in Canada. This rabbit tick was also co-infected with Borrelia lanei-like spirochetes, which constitutes a first in Canada. Overall, five ticks were concurrently infected with Babesia and Bbsl pathogens and, after the molt, could potentially co-infect humans. Notably, we provide the first authentic report of I. scapularis ticks co-infected with Bbsl and B. odocoilei in Canada. The full extent of infectious microorganisms transmitted to humans by ticks is not fully elucidated, and clinicians need to be aware of the complexity of these tick-transmitted enzootic agents on human health. Diagnosis and treatment must be administered by those with accredited medical training in tick-borne zoonosis.

Characteristics of transfusion-transmitted Babesia microti, American Red Cross 2010-2017

BACKGROUND

Babesia microti, a red blood cell (RBC) parasite transmitted naturally to vertebrate hosts by ixodid ticks, is endemic to the northeastern and upper midwestern United States, with the geographic range of infected ticks expanding. B. microti is a blood safety issue with >200 transfusion-transmissions reported.

METHODS

The American Red Cross's Hemovigilance program investigated hospital-reported transfusion-transmitted babesiosis (TTB) cases. Follow-up samples from involved donors were tested for B. microti antibodies and parasite DNA, the latter by real-time polymerase chain reaction (PCR). Test-positive donors were permanently deferred from future donations.

RESULTS

B. microti-positive donors were implicated in 77 of 143 suspect TTB cases investigated from 2010 through 2017. In four cases, two positive donors were identified for a total of 81 positive donors. In three cases, a RBC unit was split and components transfused multiple times to the same pediatric recipient. RBCs were the transmitting product in all cases. At follow-up, all involved donors were antibody positive; 25 donors were also PCR positive. Positive donations were collected throughout the year, peaking in the summer. Most donors (78) were resident of, or traveled to (2), an endemic state. One donor resided in a non-endemic state without relevant travel history. One fatality listed babesia as a contributing factor. No implicated donation was screened by an investigational protocol.

CONCLUSIONS

Babesiosis remains a blood safety issue. Prior to FDA-licensed screening test availability and final FDA Guidance, blood collectors in endemic states investigationally tested none, a portion, or all collections. Future expanded testing will reduce the frequency of TTB cases.

Tissue and blood protozoa including toxoplasmosis, Chagas disease, leishmaniasis, Babesia, Acanthamoeba, Balamuthia, and Naegleria in solid organ transplant recipients- Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of tissue and blood protozoal infections in the pre- and post-transplant period. Significant new developments in the field have made it necessary to divide the previous single guideline published in 2013 into two sections, with the intestinal parasites separated from this guideline devoted to tissue and blood protozoa. The current update reflects the increased focus on donor screening and risk-based recipient monitoring for parasitic infections. Increased donor testing has led to new recommendations for recipient management of Toxoplasma gondii and Trypanosoma cruzi. Molecular diagnostics have impacted the field, with access to rapid diagnostic testing for malaria and polymerase chain reaction testing for Leishmania. Changes in Babesia treatment regimens in the immunocompromised host are outlined. The risk of donor transmission of free-living amebae infection is reviewed. Changing immigration patterns and the expansion of transplant medicine in developing countries has contributed to the recognition of parasitic infections as an important threat to transplant outcomes. Medications such as benznidazole and miltefosine are now available to US prescribers as access to treatment of tissue and blood protozoa is increasingly prioritized.

Transfusion-Transmitted Babesiosis

Babesiosis is most commonly caused by Babesia microti and is transmitted via the bite of an infected Ixodes spp tick. However, Babesia is also transmitted via blood transfusion. In the United States, the first case of transfusion-transmitted babesiosis was recognized in 1979, and in recent years, the incidence has rapidly increased. Because most of the infected blood donors do not experience any symptoms, they pose a significant risk to the blood supply. Donor deferral for a history of babesiosis is currently performed but is ineffective. In March 2018, the FDA licensed a DNA PCR and antibody assay that were used in tandem in pivotal trials for screening blood donors for B microti; with other assays still being evaluated under investigational new drug protocols. Blood donation screening is essential to reducing the risk of transfusion-transmitted babesiosis, which is why blood centers collecting in geographic regions of highest risk have been testing since approximately 2010. Investigational NAT assays of higher sensitivity are pending FDA review. Further, in July 2018, the FDA issued a draft guidance for reducing the risk of transfusion-transmitted babesiosis. Release of the final guidance may be postponed until sensitivities and specificities of all current and potential strategies have been properly evaluated.

Human Babesiosis Caused by Babesia duncani Has Widespread Distribution across Canada

Human babesiosis caused by Babesia duncani is an emerging infectious disease in Canada. This malaria-like illness is brought about by a protozoan parasite infecting red blood cells. Currently, controversy surrounds which tick species are vectors of B. duncani. Since the availability of a serological or molecular test in Canada for B. duncani has been limited, we conducted a seven-year surveillance study (2011–2017) to ascertain the occurrence and geographic distribution of B. duncani infection country-wide. Surveillance case data for human B. duncani infections were collected by contacting physicians and naturopathic physicians in the United States and Canada who specialize in tick-borne diseases. During the seven-year period, 1119 cases were identified. The presence of B. duncani infections was widespread across Canada, with the highest occurrence in the Pacific coast region. Patients with human babesiosis may be asymptomatic, but as this parasitemia progresses, symptoms range from mild to fatal. Donors of blood, plasma, living tissues, and organs may unknowingly be infected with this piroplasm and are contributing to the spread of this zoonosis. Our data show that greater awareness of human babesiosis is needed in Canada, and the imminent threat to the security of the Canadian blood supply warrants further investigation. Based on our epidemiological findings, human babesiosis should be a nationally notifiable disease in Canada. Whenever a patient has a tick bite, health practitioners must watch for B. duncani infections, and include human babesiosis in their differential diagnosis.