EDITORIAL: The problem of transfusion-transmitted babesiosis

Human Babesiosis

Babesiosis is caused by intraerythrocytic parasites that are transmitted primarily by ticks, infrequently through blood transfusion, and rarely through transplacental transmission or organ transplantation. Human babesiosis is found throughout the world, but the incidence is highest in the Northeast and upper Midwestern United States. Babesiosis has clinical features that resemble malaria and can be fatal in immunocompromised and older patients. Diagnosis is confirmed by identification of Babesia parasites on blood smear or Babesia DNA with polymerase chain reaction. Standard treatment consists of atovaquone and azithromycin or clindamycin and quinine for 7 to 10 days.

Interactions between Babesia microti merozoites and rat kidney cells in a short-term in vitro culture and animal model

Babesiosis is one of the most common infections in free-living animals and is rapidly becoming significant among human zoonoses. Cases of acute renal failure in humans caused by Babesia spp. have been described in the literature. The kidneys are characterised by intense blood flow through the blood vessels, which increases the likelihood of contact with the intra-erythrocyte parasite. The aim of this study was to observe the influence of B. microti (ATCC 30221) on renal epithelial cells in vitro cultured (NRK-52E line) and Wistar rats' kidney. Both NRK-52E cells and rats' kidney sections were analysed by light microscopy, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH). Necrotic changes in renal epithelial cells have been observed in vitro and in vivo. In many cross-sections through the rats' kidney, adhesion of blood cells to the vascular endothelium, accumulation of erythrocytes and emboli were demonstrated. In NRK-52E culture, elements with a distinctly doubled cell membrane resembling B. microti were found inside the cytoplasm and adjacent to the cell layer. The study indicates a chemotactic tendency for B. microti to adhere to the renal tubules' epithelium, a possibility of piroplasms entering the renal epithelial cells, their proliferation within the cytoplasm and emboli formation.

Rise in Babesiosis Cases, Pennsylvania, USA, 2005-2018

Babesiosis is an emerging infection in the state of Pennsylvania, and clinicians need to be made aware of its clinical manifestations as well as the risk factors associated with severe disease. Before 2010, our tertiary academic center in central Pennsylvania previously saw zero cases of babesiosis. We saw our first confirmed case of Babesia infection acquired in Pennsylvania in 2011; we recorded 2 confirmed cases in 2017 and 4 confirmed cases in 2018. All 4 cases from 2018 were thought to be acquired in southcentral Pennsylvania counties, whereas prior reports of cases were predominately in the southeast and northeast counties of the state.

Transfusion-associated babesiosis in China: A case report

Babesiosis, a novel zoonosis, is endemic in the Northeast and Midwest United States. This disease is primarily transmitted by ticks and less commonly transmitted through blood transfusion. Here, we present a case of human babesiosis of unknown etiology. The patient may have been infected through blood transfusion. This patient had fever for more than 1 month, accompanied by fatigue, anemia, jaundice, and other symptoms. Clinical improvement was unsatisfactory with antibiotics. Subsequently, peripheral blood smears showed many circulating forms of parasites,morphologically consistent with Babesia in red blood cells. Gene sequencing suggested Babesia microti. We treated the patient with azithromycin combined with other symptomatic supportive treatment. Finally, the patient recovered and was discharged. The intensity of babesiosis ranges from mild to severe and can be fatal, so early diagnosis and treatment are warranted.

Blood Transfusion-Associated Infections in the Twenty-First Century: New Challenges

Blood transfusions are vital components of modern medical treatment to which there is no viable alternative despite efforts to create artificial blood. Each year thousands of lives are saved by blood transfusions in every country of the world. However, blood and blood products can result in significant adverse events including immunologic reactions, infections, inefficacy, and others which can sometimes result in death and severe disability. Thus, the sustainability of safe blood systems and costs are considered to be at crisis level. In industrialized countries, the risk of transfusion-transmitted infections such as HIV, syphilis, hepatitis viruses B and C are very low [generally [<1 in a million units], but in developing countries [especially in Africa] blood safety is still not assured. Compounding the problem of blood/product safety with respect to infectious agents are new emerging infectious microbes that are not being routinely tested for in blood that are donated. This chapter reviews the infectious risk of blood transfusions, types, mode and geographic variation, and the methods being used by blood services to attenuate and prevent these risks.

Human babesiosis

Babesiosis is a worldwide emerging tick-borne disease that is increasing in frequency and geographic range. It imposes a significant health burden, especially on those who are immunocompromised and those who acquire the infection through blood transfusion. Death from babesiosis occurs in up to 20 percent of these groups. Diagnosis is confirmed with identification of typical intraerythrocytic parasites on a thin blood smear or Babesia DNA using PCR. Treatment consists of atovaquone and azithromycin or clindamycin and quinine, and exchange transfusion in severe cases. Personal and communal protective measures can limit the burden of infection but it is important to recognize that none of these measures are likely to prevent the continued expansion of Babesia into non-endemic areas.

Babesia microti from humans and ticks hold a genomic signature of strong population structure in the United States

Background

Babesia microti is an emerging tick-borne apicomplexan parasite with increasing geographic range and incidence in the United States. The rapid expansion of B. microti into its current distribution in the northeastern USA has been due to the range expansion of the tick vector, Ixodes scapularis, upon which the causative agent is dependent for transmission to humans.

Results

To reconstruct the history of B. microti in the continental USA and clarify the evolutionary origin of human strains, we used multiplexed hybrid capture of 25 B. microti isolates obtained from I. scapularis and human blood. Despite low genomic variation compared with other Apicomplexa, B. microti was strongly structured into three highly differentiated genetic clusters in the northeastern USA. Bayesian analyses of the apicoplast genomes suggest that the origin of the current diversity of B. microti in northeastern USA dates back 46 thousand years with a signature of recent population expansion in the last 1000 years. Human-derived samples belonged to two rarely intermixing clusters, raising the possibility of highly divergent infectious phenotypes in humans.

Conclusions

Our results validate the multiplexed hybrid capture strategy for characterizing genome-wide diversity and relatedness of B. microti from ticks and humans. We find strong population structure in B. microti samples from the Northeast indicating potential barriers to gene flow.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3225-x) contains supplementary material, which is available to authorized users.

A targeted immunomic approach identifies diagnostic antigens in the human pathogen Babesia microti

BACKGROUND

Babesia microti is a protozoan parasite responsible for the majority of reported cases of human babesiosis and a major risk to the blood supply. Laboratory screening of blood donors may help prevent transfusion-transmitted babesiosis but there is no Food and Drug Administration-approved screening method yet available. Development of a sensitive, specific, and highly automated B. microti antibody assay for diagnosis of acute babesiosis and blood screening could have an important impact on decreasing the health burden of B. microti infection.

STUDY DESIGN AND METHODS

Herein, we take advantage of recent advances in B. microti genomic analyses, field surveys of the reservoir host, and human studies in endemic areas to apply a targeted immunomic approach to the discovery of B. microti antigens that serve as signatures of active or past babesiosis infections. Of 19 glycosylphosphatidylinositol (GPI)-anchored protein candidates (BmGPI1-19) identified in the B. microti proteome, 17 were successfully expressed, printed on a microarray chip, and used to screen sera from uninfected and B. microti-infected mice and humans to determine immune responses that are associated with active and past infection.

RESULTS

Antibody responses to various B. microti BmGPI antigens were detected and BmGPI12 was identified as the best biomarker of infection that provided high sensitivity and specificity when used in a microarray antibody assay.

CONCLUSION

BmGPI12 alone or in combination with other BmGPI proteins is a promising candidate biomarker for detection of B. microti antibodies that might be useful in blood screening to prevent transfusion-transmitted babesiosis.

Quantitative PCR for detection of Babesia microti in Ixodes scapularis ticks and in human blood

Babesia microti, the primary cause of human babesiosis in the United States, is transmitted by Ixodes scapularis ticks; transmission may also occur through blood transfusion and transplacentally. Most infected people experience a viral-like illness that resolves without complication, but those who are immunocompromised may develop a serious and prolonged illness that is sometimes fatal. The geographic expansion and increasing incidence of human babesiosis in the northeastern and midwestern United States highlight the need for high-throughput sensitive and specific assays to detect parasites in both ticks and humans with the goals of improving epidemiological surveillance, diagnosis of acute infections, and screening of the blood supply. Accordingly, we developed a B. microti-specific quantitative PCR (qPCR) assay (named BabMq18) designed to detect B. microti DNA in tick and human blood samples using a primer and probe combination that targets the 18S rRNA gene of B. microti. This qPCR assay was compared with two nonquantitative B. microti PCR assays by testing tick samples and was found to exhibit higher sensitivity for detection of B. microti DNA. The BabMq18 assay has a detection threshold of 10 copies per reaction and does not amplify DNA in I. scapularis ticks infected with Babesia odocoilei, Borrelia burgdorferi, Borrelia miyamotoi, or Anaplasma phagocytophilum. This highly sensitive and specific qPCR assay can be used for detection of B. microti DNA in both tick and human samples. Finally, we report the prevalence of B. microti infection in field-collected I. scapularis nymphs from three locations in southern New England that present disparate incidences of human babesiosis.

Preventing transfusion-transmitted babesiosis: preliminary experience of the first laboratory-based blood donor screening program

BACKGROUND

Babesiosis is the most common transfusion-transmitted infection reported to the Food and Drug Administration (FDA). We developed and implemented the first laboratory-based blood donor screening program for Babesia microti to help reduce and prevent transfusion-transmitted babesiosis (TTB) and report results for the initial year.

STUDY DESIGN AND METHODS

Selective B. microti donor screening was performed using real-time polymerase chain reaction (PCR) and indirect immunofluorescence assay (IFA) to reduce the incidence of TTB in neonates and pediatric sickle cell and thalassemia patients under an FDA-approved investigational new drug application. We compared the reports of TTB in these patients in the first 12 months of the study with those of patients who received unscreened blood from 2005 to 2010.

RESULTS

There were 2113 units tested with 2086 negative results, 26 positive IFA results (1.23%), and one indeterminate PCR result (0.05%). No reported case of TTB occurred with any B. microti-screened unit transfused to the targeted patients (0/787 units) or to any patient who received the screened units (0/2086 units). Before screening, there were seven cases of TTB in neonates, sickle cell, and thalassemia patients from 6500 unscreened units (one case/929 units) and 24 cases in the total transfused population from 496,545 units distributed (one case/20,686 units).

CONCLUSION

Implementation of B. microti IFA and PCR screening is compatible with blood center operations to provide tested units. While the results after 1 year are not powered to demonstrate a change in the rate of TTB after testing, they are encouraging.

One Health approach to identify research needs in bovine and human babesioses: workshop report

BACKGROUND

Babesia are emerging health threats to humans and animals in the United States. A collaborative effort of multiple disciplines to attain optimal health for people, animals and our environment, otherwise known as the One Health concept, was taken during a research workshop held in April 2009 to identify gaps in scientific knowledge regarding babesioses. The impetus for this analysis was the increased risk for outbreaks of bovine babesiosis, also known as Texas cattle fever, associated with the re-infestation of the U.S. by cattle fever ticks.

RESULTS

The involvement of wildlife in the ecology of cattle fever ticks jeopardizes the ability of state and federal agencies to keep the national herd free of Texas cattle fever. Similarly, there has been a progressive increase in the number of cases of human babesiosis over the past 25 years due to an increase in the white-tailed deer population. Human babesiosis due to cattle-associated Babesia divergens and Babesia divergens-like organisms have begun to appear in residents of the United States. Research needs for human and bovine babesioses were identified and are presented herein.

CONCLUSIONS

The translation of this research is expected to provide veterinary and public health systems with the tools to mitigate the impact of bovine and human babesioses. However, economic, political, and social commitments are urgently required, including increased national funding for animal and human Babesia research, to prevent the re-establishment of cattle fever ticks and the increasing problem of human babesiosis in the United States.