Babesiosis in immunocompetent patients, Europe

Multiomics analysis reveals B. MO1 as a distinct Babesia species and provides insights into its evolution and virulence

Babesiosis, caused by protozoan parasites of the genus Babesia , is an emerging tick-borne disease of significance for both human and animal health. Babesia parasites infect erythrocytes of vertebrate hosts where they develop and multiply rapidly to cause the pathological symptoms associated with the disease. The identification of various Babesia species underscores the ongoing risk of new zoonotic pathogens capable of infecting humans, a concern amplified by anthropogenic activities and environmental shifts impacting the distribution and transmission dynamics of parasites, their vectors, and reservoir hosts. One such species, Babesia MO1, previously implicated in severe cases of human babesiosis in the midwestern United States, was initially considered closely related to B. divergens , the predominant agent of human babesiosis in Europe. Yet, uncertainties persist regarding whether these pathogens represent distinct variants of the same species or are entirely separate species. We show that although both B. MO1 and B. divergens share similar genome sizes, comprising three nuclear chromosomes, one linear mitochondrial chromosome, and one circular apicoplast chromosome, major differences exist in terms of genomic sequence divergence, gene functions, transcription profiles, replication rates and susceptibility to antiparasitic drugs. Furthermore, both pathogens have evolved distinct classes of multigene families, crucial for their pathogenicity and adaptation to specific mammalian hosts. Leveraging genomic information for B. MO1, B. divergens , and other members of the Babesiidae family within Apicomplexa provides valuable insights into the evolution, diversity, and virulence of these parasites. This knowledge serves as a critical tool in preemptively addressing the emergence and rapid transmission of more virulent strains.

Retrospective study of the epidemiological risk and serological diagnosis of human babesiosis in Asturias, Northwestern Spain

BACKGROUND

Babesiosis is a globally growing tick-borne disease in humans. Severe babesiosis caused by Babesia divergens has been reported in two patients from Asturias (Northwestern Spain), suggesting an undetected risk for the disease. To analyze this risk, we retrospectively evaluated the seroprevalence of babesiosis in the Asturian population from 2015 through 2017, a period covering the intermediate years in which these two severe cases occurred.

METHODS

Indirect fluorescent assay (IFA) and Western blot (WB) were performed to detect B. divergens IgG antibodies in 120 serum samples from Asturian patients infected with the tick-transmitted spirochete Borrelia burgdorferi sensu lato, a condition that indicates exposure to tick bites.

RESULTS

This retrospective study confirmed a B. divergens seroprevalence rate of 39.2% according to IFA results. B. divergens incidence was 7.14 cases/100,000 population, exceeding previously reported seroprevalence rates. No differences in epidemiology and risk factors were found between patients infected solely with B. burgdorferi s.l. and those infected with B. burgdorferi s.l. and with IgG antibodies against B. divergens. This last group of patients lived in Central Asturias, had a milder clinical course and, according to WB results, developed different humoral responses against B. divergens.

CONCLUSIONS

Babesia divergens parasites have circulated for several years in Asturias. Epidemiological evidence of babesiosis makes Asturias an emerging risk area for this zoonosis. Human babesiosis could also be relevant in other Spanish and European regions affected by borreliosis. Hence, the potential risk of babesiosis on human health in Asturias and other European forest regions needs to be addressed by the health authorities.

Characteristics of Human Babesiosis in Europe

One of the Editor's choice articles in 2021 published in Pathogens was a review of human babesiosis in Europe [...].

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.

Extraordinary high level of propagation of Babesia divergens in severe human babesiosis

Babesias are obligate apicomplexan parasites that affect the red blood cells (RBCs) of animals. Humans can serve as accidental hosts for them. Asexual reproduction of a parasite occurs in a vertebrate host through asynchronous binary fission, yielding a complex pleomorphic population of intraerythrocytic forms. In natural hosts (Bos taurus), paired pyriforms (‘figure 8’) of Babesia divergens are usual, but tetrads (‘Maltese Cross’) are very rare (only in 0.02% infected erythrocytes); in humans, however, up to 5% of infected erythrocytes show tetrads. The current study shows that B. divergens proliferating in an accidental human host can promote extraordinarily high level of fission. This phenomenon is expressed as the simultaneous division of the parasite into 6 and possibly a greater number of merozoites, forming a ‘daisy head’ (vs the usual 2, less often 4 merozoites). Reproduction is possible without egressing merozoites from the erythrocyte, which results in multi-occupancy of an RBC (≥5 parasites per RBC). An unusually high polyparasitism – up to 14 parasites developed in the affected erythrocytes – was observed. This phenomenon is rare in natural hosts (usually ≤5), but when B. divergens is cultured in vitro it can be 10–12.

The Global Emergence of Human Babesiosis

Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa that are primarily transmitted by hard-bodied (ixodid) ticks and rarely through blood transfusion, perinatally, and organ transplantation. More than 100 Babesia species infect a wide spectrum of wild and domestic animals worldwide and six have been identified as human pathogens. Babesia microti is the predominant species that infects humans, is found throughout the world, and causes endemic disease in the United States and China. Babesia venatorum and Babesia crassa-like agent also cause endemic disease in China. Babesia divergens is the predominant species in Europe where fulminant cases have been reported sporadically. The number of B. microti infections has been increasing globally in recent decades. In the United States, more than 2000 cases are reported each year, although the actual number is thought to be much higher. In this review of the epidemiology of human babesiosis, we discuss epidemiologic tools used to monitor disease location and frequency; demographics and modes of transmission; the location of human babesiosis; the causative Babesia species in the Americas, Europe, Asia, Africa, and Australia; the primary clinical characteristics associated with each of these infections; and the increasing global health burden of this disease.

The New Human Babesia sp. FR1 Is a European Member of the Babesia sp. MO1 Clade

In Europe, Babesia divergens is responsible for most of the severe cases of human babesiosis. In the present study, we describe a case of babesiosis in a splenectomized patient in France and report a detailed molecular characterization of the etiological agent, named Babesia sp. FR1, as well as of closely related Babesia divergens, Babesia capreoli and Babesia sp. MO1-like parasites. The analysis of the conserved 18S rRNA gene was supplemented with the analysis of more discriminant markers involved in the red blood cell invasion process: rap-1a (rhoptry-associated-protein 1) and ama-1 (apical-membrane-antigen 1). The rap-1a and ama-1 phylogenetic analyses were congruent, placing Babesia sp. FR1, the new European etiological agent, in the American cluster of Babesia sp. MO1-like parasites. Based on two additional markers, our analysis confirms the clear separation of B. divergens and B. capreoli. Babesia sp. MO1-like parasites should also be considered as a separate species, with the rabbit as its natural host, differing from those of B. divergens (cattle) and B. capreoli (roe deer). The natural host of Babesia sp. FR1 remains to be discovered.

Human Babesiosis in Europe

Babesiosis is attracting increasing attention as a worldwide emerging zoonosis. The first case of human babesiosis in Europe was described in the late 1950s and since then more than 60 cases have been reported in Europe. While the disease is relatively rare in Europe, it is significant because the majority of cases present as life-threatening fulminant infections, mainly in immunocompromised patients. Although appearing clinically similar to human babesiosis elsewhere, particularly in the USA, most European forms of the disease are distinct entities, especially concerning epidemiology, human susceptibility to infection and clinical management. This paper describes the history of the disease and reviews all published cases that have occurred in Europe with regard to the identity and genetic characteristics of the etiological agents, pathogenesis, aspects of epidemiology including the eco-epidemiology of the vectors, the clinical courses of infection, diagnostic tools and clinical management and treatment.

Detection of Babesia RNA and DNA in whole blood samples from US blood donations

Background

Human babesiosis is a zoonotic infection caused by an intraerythrocytic parasite. The highest incidence of babesiosis is in the United States, although cases have been reported in other parts of the world. Due to concerns of transfusion‐transmitted babesiosis, the US Food and Drug Administration (FDA) recommended year‐round regional testing for Babesia by nucleic acid testing or use of an FDA‐approved device for pathogen reduction. A new molecular test, cobas Babesia (Roche Molecular Systems, Inc.), was evaluated for the detection of the four species that cause human disease, Babesia microti, Babesia duncani, Babesia divergens, and Babesia venatorum.

Study design and methods

Analytical performance was evaluated followed by clinical studies on whole blood samples from US blood donations collected in a special tube containing a chaotropic reagent that lyses the red cells and preserves nucleic acid. Sensitivity and specificity of the test in individual samples (individual donation testing [IDT]) and in pools of six donations were determined.

Results

Based on analytical studies, the claimed limit of detection of cobas Babesia for B. microti is 6.1 infected red blood cells (iRBC)/mL (95% confidence interval [CI]: 5.0, 7.9); B. duncani was 50.2 iRBC/mL (95% CI: 44.2, 58.8); B. divergens was 26.1 (95% CI: 22.3, 31.8); and B. venatorum was 40.0 iRBC/mL (95% CI: 34.1, 48.7). The clinical specificity for IDT was 99.999% (95% CI: 99.996, 100) and 100% (95% CI: 99.987, 100) for pools of six donations.

Conclusion

cobas Babesia enables donor screening for Babesia species with high sensitivity and specificity.

A historical review of Babesia spp. associated with deer in Europe: Babesia divergens/Babesia divergens-like, Babesia capreoli, Babesia venatorum, Babesia cf. odocoilei

This review is intended to provide an overview of the occurrence and diversity of Babesia spp. in European deer. Babesiosis is an emerging vector-borne disease with negative implications on animal and public health. Cervidae are important hosts for Ixodidae ticks, playing a critical role in the epidemiology of the parasite. Deer are susceptible to different Babesia spp., some of them with zoonotic potential. The infection is usually asymptomatic with high prevalence rates, although some fatal cases due to B. capreoli and B. venatorum have been reported. In Europe, 3 main Babesia spp. have been described in deer: Babesia divergens/B. divergens-like, B. capreoli and B. venatorum. Additionally, close relatives of B. odocoilei, the Babesia species of the American white-tailed deer (Odocoileus virginianus), have been isolated in several European countries. The occurrence of B. divergens/B. divergens-like generated concerns about the role of cervidae in the life cycle of the parasite, and the potential threat for public health. Few human cases have been attributed to B. venatorum so far, including hunters. Although this species is strictly related to the presence of roe deer (Capreolus capreolus), it has been occasionally reported in moose (Alces alces) and captive reindeer (Rangifer tarandus). Over recent years, vector-borne diseases received increased attention from International Organizations. However, technical difficulties persist, affecting surveillance efficiency. Given the veterinary and zoonotic importance of babesiosis, the author advocates the need for an effective monitoring at wildlife-domestic animals-humans interface and the implementation of management plans to reduce the risk of Babesia spp. infection for both humans and domestic animals.

Three Babesia species in Ixodes ricinus ticks from migratory birds in Sweden

Background

Migratory birds can cross geographical and environmental barriers and are thereby able to facilitate transmission of tick-borne pathogens both as carriers of infected ticks and as reservoirs of pathogenic microorganisms. Ixodes ricinus is one of the most abundant tick species in the Northern Hemisphere and a main vector of several Babesia species, some which pose a potential threat to human and animal health. At present only two cases of overt babesiosis in humans have so far been reported in Sweden. To better understand the potential role of birds as disseminators of zoonotic Babesia protozoan parasites, we investigated the presence of Babesia species in ticks removed from migratory birds.

Methods

Ticks were collected from birds captured at Ottenby Bird Observatory, south-eastern Sweden, from March to November 2009. Ticks were molecularly identified to species, and morphologically to developmental stage, and the presence of Babesia protozoan parasites was determined by real-time PCR.

Results

In total, 4601 migratory birds of 65 species were examined for tick infestation. Ticks removed from these birds have previously been investigated for the presence of Borrelia bacteria and the tick-borne encephalitis virus. In the present study, a total of 1102 ticks were available for molecular analysis of Babesia protozoan parasites. We found that 2.4% of the ticks examined, all I. ricinus, were positive for mammal-associated Babesia species. Out of all Babesia-positive samples, Babesia venatorum was the most prevalent (58%) species, followed by Babesia microti (38%) and Babesia capreoli (4.0%). B. venatorum and B. capreoli were detected in I. ricinus larvae, whereas B. microti was only present in I. ricinus nymphs. This supports the view that the two first-mentioned species are vertically (transovarially) transmitted in the tick population, in contrast to B. microti. The largest number of Babesia-infected ticks was removed from the common redstart (Phoenicurus phoenicurus) and European robin (Erithacus rubecula).

Conclusions

This study reveals that Babesia protozoan parasites are present in ticks infesting migratory birds in south-eastern Sweden, which could potentially lead to the dissemination of these tick-borne microorganisms into new areas, thus posing a threat to humans and other mammals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04684-8.

Emerging Human Babesiosis with "Ground Zero" in North America

The first case of human babesiosis was reported in the literature in 1957. The clinical disease has sporadically occurred as rare case reports in North America and Europe in the subsequent decades. Since the new millennium, especially in the last decade, many more cases have apparently appeared not only in these regions but also in Asia, South America, and Africa. More than 20,000 cases of human babesiosis have been reported in North America alone. In several cross-sectional surveys, exposure to Babesia spp. has been demonstrated within urban and rural human populations with clinical babesiosis reported in both immunocompromised and immunocompetent humans. This review serves to highlight the widespread distribution of these tick-borne pathogens in humans, their tick vectors in readily accessible environments such as parks and recreational areas, and their phylogenetic relationships.

Tick-borne zoonoses and commonly used diagnostic methods in human and veterinary medicine

Around the world, human health and animal health are closely linked in terms of the One Health concept by ticks acting as vectors for zoonotic pathogens. Animals do not only maintain tick cycles but can either be clinically affected by the same tick-borne pathogens as humans and/or play a role as reservoirs or sentinel pathogen hosts. However, the relevance of different tick-borne diseases (TBDs) may vary in human vs. veterinary medicine, which is consequently reflected by the availability of human vs. veterinary diagnostic tests. Yet, as TBDs gain importance in both fields and rare zoonotic pathogens, such as Babesia spp., are increasingly identified as causes of human disease, a One Health approach regarding development of new diagnostic tools may lead to synergistic benefits. This review gives an overview on zoonotic protozoan, bacterial and viral tick-borne pathogens worldwide, discusses commonly used diagnostic techniques for TBDs, and compares commercial availability of diagnostic tests for humans vs. domestic animals, using Germany as an example, with the aim of highlighting existing gaps and opportunities for collaboration in a One Health framework.

Bovine Babesiosis Diagnosed in Formalin-Fixed, Paraffin-Embedded Tissues by Using In Situ Hybridization

Bovine babesiosis, caused by Babesia divergens, is in general a rare disease in Europe. Nonetheless, local outbreaks can cause severe economic damage, and postmortem identification represents a diagnostic challenge. During a recent outbreak in May 2018 in northern Germany, 21 animals of a herd of 150 cattle died within 40 days having had clinical signs of fever and hemoglobinuria. Gross examination of 4 of the 21 deceased animals revealed a tick infestation, jaundice, and dark brown staining of urine and kidneys. Histologically, there were iron-positive deposits, hyperplasia of the red pulp of the spleen, and centrilobular necrosis of hepatocytes. In several locations, small basophilic granules suggestive of intraerythrocytic parasites were visible in hematoxylin-eosin- and Giemsa-stained sections. Peripheral blood smears from a living cow from the herd and polymerase chain reaction (PCR) of feeding ticks revealed B. divergens infection. In situ hybridization (ISH) was applied on formalin-fixed, paraffin-embedded (FFPE) tissue of the necropsied cattle to confirm babesiosis in these animals postmortem. Digoxigenin-labeled DNA probes were generated based on a specific nucleotide sequence for B. divergens, obtained by PCR and sequencing of DNA isolates from infected Ixodes ricinus ticks from deceased cattle. ISH using these probes allowed postmortem diagnosis of B. divergens infection in routinely fixed FFPE tissues.

Management strategies for human babesiosis

INTRODUCTION

Human babesiosis is reported throughout the world and is endemic in the northeastern and northern Midwestern United States and northeastern China. Transmission is primarily through hard bodied ticks. Most cases of severe disease occur in immunocompromised individuals and may result in prolonged relapsing disease or death.

AREAS COVERED

We provide a summary of evidence supporting current treatment recommendations for immunocompetent and immunocompromised individuals experiencing babesiosis.

EXPERT OPINION

Most cases of human babesiosis are successfully treated with atovaquone and azithromycin or clindamycin and quinine. Severe disease may require prolonged treatment.

Clinical/serological outcome in humans bitten by Babesia species positive Ixodes ricinus ticks in Sweden and on the Åland Islands

The risk of contracting babesiosis after a tick bite in Sweden and on the Åland Islands, Finland, is unknown. We investigated clinical and serological outcomes in people bitten by Ixodes ricinus ticks positive for Babesia species. Ticks, blood and questionnaires were obtained from study participants in Sweden and on the Åland Islands. Sixty-five of 2098 (3.1 %) ticks were positive by real-time PCR. Three Babesia species were detected, Babesia microti (n = 33), B. venatorum (n = 27) and B. capreoli (n = 5), the latter species not known to cause human infection. Half (46 %) of the Babesia PCR-positive ticks also contained Borrelia spp. Fifty-three participants bitten by a Babesia PCR-positive tick and a control group bitten by a Babesia PCR-negative tick were tested for B. microti IgG antibodies by IFA. The overall seroprevalence was 4.4 %, but there was no significant difference between the groups. None of the participants seroconverted and no participant with a Babesia PCR-positive tick sought medical care or reported symptoms suggestive of babesiosis. Given the prevalence of Babesia in I. ricinus ticks in southern Sweden and on the Åland Islands, babesiosis should be considered a possible diagnosis in symptomatic residents who seek medical care following tick exposure.

Evaluation of Disease Causality of Rare Ixodes ricinus-Borne Infections in Europe

In Europe, Ixodes ricinus ticks transmit pathogens such as Borrelia burgdorferi sensu lato and tick-borne encephalitis virus (TBEV). In addition, there is evidence for transmission to humans from I. ricinus of Anaplasma phagocytophilum, Babesia divergens, Babesia microti, Babesia venatorum, Borrelia miyamotoi, Neoehrlichia mikurensis, Rickettsia helvetica and Rickettsia monacensis. However, whether infection with these potential tick-borne pathogens results in human disease has not been fully demonstrated for all of these tick-borne microorganisms. To evaluate the available evidence for a causative relation between infection and disease, the current study analyses European case reports published from 2008 to 2018, supplemented with information derived from epidemiological and experimental studies. The evidence for human disease causality in Europe found in this review appeared to be strongest for A. phagocytophilum and B. divergens. Nonetheless, some knowledge gaps still exist. Importantly, comprehensive evidence for pathogenicity is lacking for the remaining tick-borne microorganisms. Such evidence could be gathered best through prospective studies, for example, studies enrolling patients with a fever after a tick bite, the development of specific new serological tools, isolation of these microorganisms from ticks and patients and propagation in vitro, and through experimental studies.

Emerging Tick-Borne Diseases

Increases in tick-borne disease prevalence and transmission are important public health issues. Efforts to control these emerging diseases are frustrated by the struggle to control tick populations and to detect and treat infections caused by the pathogens that they transmit. This review covers tick-borne infectious diseases of nonrickettsial bacterial, parasitic, and viral origins. While tick surveillance and tracking inform our understanding of the importance of the spread and ecology of ticks and help identify areas of risk for disease transmission, the vectors are not the focus of this document. Here, we emphasize the most significant pathogens that infect humans as well as the epidemiology, clinical features, diagnosis, and treatment of diseases that they cause. Although detection via molecular or immunological methods has improved, tick-borne diseases continue to remain underdiagnosed, making the scope of the problem difficult to assess. Our current understanding of the incidence of tick-borne diseases is discussed in this review. An awareness of the diseases that can be transmitted by ticks in specific locations is key to detection and selection of appropriate treatment. As tick-transmitted pathogens are discovered and emerge in new geographic regions, our ability to detect, describe, and understand the growing public health threat must also grow to meet the challenge.

Babesia divergens glycosylphosphatidylinositols modulate blood coagulation and induce Th2-biased cytokine profiles in antigen presenting cells

Glycosylphosphatidylinositols (GPIs) are glycolipids described as toxins of protozoan parasites due to their inflammatory properties in mammalian hosts characterized by the production of interleukin (IL)-1, IL-12 and tumor necrosis factor (TNF)-α. In the present work, we studied the cytokines produced by antigen presenting cells in response to ten different GPI species extracted from Babesia divergens, responsible for babesiosis. Interestingly, B. divergens GPIs induced the production of anti-inflammatory cytokines (IL-2, IL-5) and of the regulatory cytokine IL-10 by macrophages and dendritic cells. In contrast to all protozoan GPIs studied until now, GPIs from B. divergens did not stimulate the production of TNF-α and IL-12, leading to a unique Th1/Th2 profile. Analysis of the carbohydrate composition of the B. divergens GPIs indicated that the di-mannose structure was different from the evolutionary conserved tri-mannose structure, which might explain the particular cytokine profile they induce. Expression of major histocompatibility complex (MHC) molecules on dendritic cells and apoptosis of mouse peritoneal cells were also analysed. B. divergens GPIs did not change expression of MHC class I, but decreased expression of MHC class II at the cell surface, while GPIs slightly increased the percentages of apoptotic cells. During pathogenesis of babesiosis, the inflammation-coagulation auto-amplification loop can lead to thrombosis and the effect of GPIs on coagulation parameters was investigated. Incubation of B. divergens GPIs with rat plasma ex vivo led to increase of fibrinogen levels and to prolonged activated partial thromboplastin time, suggesting a direct modulation of the extrinsic coagulation pathway by GPIs.

Human babesiosis in Alsace

OBJECTIVES

Human babesiosis is a rare parasitic anthropozoonosis transmitted to humans by tick bites. Fifty-six cases of human babesiosis have been recorded in Europe. Two cases of babesiosis were reported in Alsace, France, in 2009. We performed a retrospective observational descriptive study to assess the epidemiology of the disease in Alsace.

METHODS

Patients were included if they had a positive serology result for Babesia and/or a positive blood smear and/or a positive PCR result. The tests were performed in the microbiology laboratories of the university hospitals of Strasbourg, the civil hospitals of Colmar, and the hospital of Mulhouse between January 1, 2005 and December 31, 2015. Included patients were divided into three groups: definite case group (positive PCR or positive blood smear or seroconversion), possible case group (positive serology results without seroconversion with a compatible clinical picture and without other confirmed diagnoses), and incompatible case group (positive serology results without seroconversion, without compatible clinical picture and/or with other confirmed diagnoses). The compatible clinical picture was defined by the presence of flu-like symptoms and fever (≥38°C).

RESULTS

Fifty-one patients had at least one positive result. Three cases were excluded (missing files). There were six definite cases, 12 possible cases, and 30 incompatible cases. All patients in the definite case group were immunocompetent. No deaths occurred.

CONCLUSIONS

Human babesiosis is probably underdiagnosed due to its non-specific symptoms, lack of awareness about the disease, and the difficulty in making a diagnosis.

Ticks and tick-borne diseases

Ticks are a major group of arthropod vectors, characterized by the diversity of pathogens they transmit, by their impact on human and animal health, and by their socioeconomic implication especially in countries of the Southern Hemisphere. In Europe, Ixodes is the most important tick due to its wide distribution in the ecosystems and the variety of transmitted pathogens, in particular Borrelia (responsible for Lyme borreliosis), but also the tick-borne encephalitis virus. Their increased presence in the environment since the beginning of the 20th century is undeniable, because of major modifications in the biodiversity caused by humans. Increasing the awareness of health professionals and the general population is required to achieve better control of these infections. Thus, "a better understanding of these tick-borne diseases for a better control" is a simple but effective approach, considering their ubiquity in the environment and their particular mode of pathogen transmission (long-lasting blood meal for hard ticks and delayed transmission for bacteria and parasites). Finally, these ectoparasites are problematic due to the potential allergic reactions and other damages caused by their saliva, in humans and animals.

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.

Prevalence and co-infection with tick-borne Anaplasma phagocytophilum and Babesia spp. in red deer (Cervus elaphus) and roe deer (Capreolus capreolus) in Southern Norway

Anaplasma phagocytophilum and Babesia spp. are causative agents of tick-borne infections that are increasingly considered as a threat to animal and public health. To assess the role of cervids in the maintenance of zoonotic pathogens in Norway, we investigated the prevalence of A. phagocytophilum and Babesia spp. in free-ranging roe deer and red deer. Initial screening of spleen samples of 104 animals by multiplex real-time PCR targeting the major surface protein (msp2) gene and 18S rRNA revealed the presence of A. phagocytophilum infection in 81.1% red deer (Cervus elaphus) and 88.1% roe deer (Capreolus capreolus), and Babesia spp. parasites in 64.9% red deer and 83.6% roe deer, respectively. Co-infections were found in 62.2% red deer and 79.9% roe deer. Nested PCR and sequence analysis of partial msp4 and 18S rRNA genes were performed for molecular characterization of A. phagocytophilum strains and Babesia species. A total of eleven A. phagocytophilum msp4 gene sequence variants were identified: five different variants were 100% identical to corresponding A. phagocytophilum sequences deposited in the GenBank database, while other six sequence variants had unique nucleotide polymorphisms. Sequence analysis of the 18S rRNA gene demonstrated the presence of multiple Babesia species, including Babesia capreoli, Babesia divergens, Babesia venatorum and Babesia odocoilei/Babesia cf. odocoilei. This study is the first report demonstrating the prevalence and molecular characterization of A. phagocytophilum strains and Babesia species in roe deer and red deer in Norway. The high infection and co-infection rates with A. phagocytophilum and Babesia spp. in red deer and roe deer suggest that these cervids may play an important role in the transmission of single and multiple pathogens.

Splenic rupture from babesiosis, an emerging concern? A systematic review of current literature

Babesiosis is a relatively common tick-borne parasitic infection of erythrocytes primarily affecting the northeastern United States. Babesiosis' prevalence and presentation have earned it the monikers "malaria of the northeast" and "Nantucket fever". Clinical presentation ranges from asymptomatic infection to severe infection including acute respiratory distress syndrome (ARDS) and disseminated intravascular coagulopathy (DIC) or death. Since 2008, there have been a number of reports of splenic rupture in patients with the disease. We seek to provide a further understanding of this process, with the report of a case of splenic rupture followed by a systematic review of the current literature. We found that 87% of splenic rupture secondary to babesiosis occurred in male patients who are otherwise healthy, with an average of 56 years. Computed tomography is a reliable mode of diagnosis, and hemoperitoneum is the most common imaging finding. Patients with splenic rupture due to human babesiosis were successfully treated by various management strategies, such as conservative non-operative approach, splenic artery embolization, and splenectomy. The modality of treatment depends on patient's clinical course and hemodynamic stability, although spleen conserving strategy should be considered first whenever possible.

The Babesia divergens Asia Lineage Is Maintained through Enzootic Cycles between Ixodes persulcatus and Sika Deer in Hokkaido, Japan

Parasites of the Babesiadivergens Asia lineage, which are closely related to B. divergens in Europe and Babesia sp. strain MO1 in the United States, were recently reported in sika deer (Cervus nippon) in eastern Japan. To identify the tick vector(s) for this parasite, we conducted a field survey in Hokkaido, Japan, where the infection rate in sika deer is the highest in the country. A specific PCR system which detects and discriminates between lineages within B. divergens and between those lineages and Babesia venatorum showed that Ixodes persulcatus (11/822), but not sympatric Ixodes ovatus (0/595) or Haemaphysalis sp. (0/163) ticks, carried B. divergens Asia lineage. Genomic DNA was archived from salivary glands of partially engorged I. persulcatus females and three isolates of B. divergens Asia lineage were newly described. The 18S rRNA gene sequence of the isolates formed the Asia lineage cluster with those previously described in sika deer isolates. One salivary gland also contained parasites of Babesia microti U.S. lineage, which were subsequently isolated in a hamster in vivoB. venatorum (strain Etb5) was also detected in one I. persulcatus tick. The 18S rRNA sequence of Etb5 was 99.7% identical to that of B. venatorum (AY046575) and was phylogenetically positioned in a taxon composed of B. venatorum isolates from Europe, China, and Russia. The geographical distribution of I. persulcatus is consistent with that of B. divergens in sika deer in Japan. These results suggest that I. persulcatus is a principal vector for B. divergens in Japan and Eurasia, where I. persulcatus is predominantly distributed.IMPORTANCE The Babesiadivergens Asia lineage of parasites closely related to B. divergens in Europe and Babesia sp. MO1 in the United States was recently reported in Cervus nippon in eastern Japan. In this study, specific PCR for the Asia lineage identified 11 positives in 822 host-seeking Ixodes persulcatus ticks, a principal vector for many tick-borne disease agents. Gene sequences of three isolates obtained from DNA in salivary glands of female ticks were identical to each other and to those in C. nippon We also demonstrate the coinfection of B. divergens Asia lineage with Babesia microti U.S. lineage in a tick salivary gland and, furthermore, isolated the latter in a hamster. These results suggest that I. persulcatus is the principal vector for B. divergens as well as for B. microti, and both parasites may be occasionally cotransmitted by I. persulcatus This report will be important for public health, since infection may occur through transfusion.

Tick-borne infections and co-infections in patients with non-specific symptoms in Poland

AIM

The aim of the study was the evaluation of the frequency of infections and co-infections among patients hospitalized because of non-specific symptoms after a tick bite.

MATERIALS AND METHODS

Whole blood, serum and cerebrospinal fluid samples from 118 patients hospitalised for non-specific symptoms up to 8 weeks after tick bite from 2010 to 2013 were examined for tick-borne infections. ELISA, Western blot and/or molecular biology (PCR; fla gene; 16S rRNA; sequencing) and thin blood smears (MDD) were used. Control group included 50 healthy blood donors. All controls were tested with PCR and serology according to the same procedure as in patients.

RESULTS

Out of 118 patients 85 (72%) experienced headaches, 15 (13%) vertigo, 32 (27%) nausea, 17 (14%) vomiting, 37 (31%) muscle pain, 73 (62%) fever and 26 (22%) meningeal signs. 47.5% were infected with at least one tick-borne pathogen. Borrelia burgdorferi sensu lato infection was confirmed with ELISA, Western blot in serum and/or (PCR (fla gene) in whole blood in 29.7% cases. In blood of 11.9% patients Anaplasma phagocytophilum DNA (16S rRNA gene) was detected; in 0.9% patients 1/118 Babesia spp. DNA (18S rRNA gene) was also detected. Co-infections were observed in 5.1% of patients with non-specific symptoms. B. burgdorferi s.l. - A. phagocytophilum co-infection (5/118; 4.2%) was most common. In 1/118 (0.8%) A. phagocytophilum - Babesia spp. co-infection was detected. All controls were negative for examined pathogens.

CONCLUSIONS

Non-specific symptoms after tick bite may be caused by uncommon pathogens or co-infection, therefore it should be considered in differential diagnosis after tick bite.

A fatal case of Babesia divergens infection in Northwestern Spain

We describe a fatal case caused by the intra-erythrocytic Babesia divergens parasite in an elderly woman. This is the third case of fatal babesiosis reported in the last 15 years in Europe, and the only one in a patient with an intact spleen.

Prevalence of tick-borne pathogens in questing Ixodes ricinus ticks in urban and suburban areas of Switzerland

Background

Throughout Europe, Ixodes ricinus transmits numerous pathogens. Its widespread distribution is not limited to rural but also includes urbanized areas. To date, comprehensive data on pathogen carrier rates of I. ricinus ticks in urban areas of Switzerland is lacking.

Results

Ixodes ricinus ticks sampled at 18 (sub-) urban collection sites throughout Switzerland showed carrier rates of 0% for tick-borne encephalitis virus, 18.0% for Borrelia burgdorferi (sensu lato), 2.5% for Borrelia miyamotoi, 13.5% for Rickettsia spp., 1.4% for Anaplasma phagocytophilum, 6.2% for "Candidatus Neoehrlichia mikurensis", and 0.8% for Babesia venatorum (Babesia sp., EU1). Site-specific prevalence at collection sites with n > 45 ticks (n = 9) significantly differed for B. burgdorferi (s.l.), Rickettsia spp., and "Ca. N. mikurensis", but were not related to the habitat type. Three hundred fifty eight out of 1078 I. ricinus ticks (33.2%) tested positive for at least one pathogen. Thereof, about 20% (71/358) were carrying two or three different potentially disease-causing agents. Using next generation sequencing, we could detect true pathogens, tick symbionts and organisms of environmental or human origin in ten selected samples.

Conclusions

Our data document the presence of pathogens in the (sub-) urban I. ricinus tick population in Switzerland, with carrier rates as high as those in rural regions. Carriage of multiple pathogens was repeatedly observed, demonstrating the risk of acquiring multiple infections as a consequence of a tick bite.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2500-2) contains supplementary material, which is available to authorized users.

Tick-borne bacteria and protozoa detected in ticks collected from domestic animals and wildlife in central and southern Portugal

Ticks are vectors of many human and animal pathogens. The aim of this study was to screen bacteria and protozoa from ticks infesting domestic animals and wildlife collected in central and southern Portugal. A total of 593 ticks, comprising 465 (78.4%) adults, 122 (20.6%) nymphs, and six (1.0%) larvae, were collected from 283 hosts of 25 different species (4 domestic and 21 wild). Overall, the analysis of DNA extracts prepared from ticks collected from hosts of 11 different species in the districts of Castelo Branco, Portalegre, Lisboa, Setúbal, Beja and Faro, revealed the presence of genomic sequences from Anaplasma sp., A. ovis, Babesia sp., relapsing fever-like Borrelia sp., Ehrlichia spp., Rickettsia aeschlimannii, Ri. helvetica, Ri. massiliae, Ri. raoultii, Ri. slovaca, Candidatus Ri. barbariae, Theileria annulata and T. ovis, in specimens of Dermacentor marginatus, Hyalomma lusitanicum, Hy. marginatum, Rhipicephalus bursa and Rh. sanguineus sensu lato. The obtained results suggest the circulation of a wide variety of infectious agents, some of zoonotic concern, in hard ticks from Portugal. Further studies should be conducted to better characterize (both genetically and phenotypically) the putative novel microorganisms detected, both in what regards their potential pathogenity towards vertebrates, and to assist the implementation of effective control strategies for the management of ticks and human and animal tick-borne pathogens.

Hematologic manifestations of babesiosis

BACKGROUND

Babesiosis, a zoonotic parasitic infection transmitted by the Ixodes tick, has become an emerging health problem in humans that is attracting attention worldwide. Most cases of human babesiosis are reported in the United States and Europe. The disease is caused by the protozoa of the genus Babesia, which invade human erythrocytes and lyse them causing a febrile hemolytic anemia. The infection is usually asymptomatic or self-limited in the immunocompetent host, or follows a persistent, relapsing, and/or life threatening course with multi-organ failure, mainly in the splenectomized or immunosuppressed patients. Hematologic manifestations of the disease are common. They can range from mild anemia, to severe pancytopenia, splenic rupture, disseminated intravascular coagulopathy (DIC), or even hemophagocytic lymphohistiocytosis (HLH).

CASE PRESENTATION

A 70 year old immunocompetent female patient living in New York City presented with a persistent fever, night sweats, and fatigue of 5 days duration. Full evaluation showed a febrile hemolytic anemia along with neutropenia and thrombocytopenia. Blood smear revealed intraerythrocytic Babesia, which was confirmed by PCR. Bone marrow biopsy was remarkable for dyserythropoiesis, suggesting possible HLH, supported by other blood workup meeting HLH-2004 trial criteria.

CONCLUSION

Human babesiosis is an increasing healthcare problem in the United States that is being diagnosed more often nowadays. We presented a case of HLH triggered by Babesia microti that was treated successfully. Also, we presented the hematologic manifestations of this disease along with their pathophysiologies.

Ticks and Tick-borne diseases in Ireland

Throughout Europe interest in tick-borne agents is increasing, particularly with regard to those that can cause human disease. The reason for this is the apparent rise in the incidence of many tick-borne diseases (TBD’s). While there has never been a national survey of ticks or TBD’s in Ireland, the trend here appears to be the reverse with a decline in the incidence of some agents seemingly associated with decreasing tick numbers particularly on agricultural land. In the absence of robust baseline data, however, this development cannot be confirmed.

This review collates the limited information available from several dated published records on tick species and a small number of studies focused on certain TBD’s. Some pilot data on tick density and TBD agents collected in 2016 are also presented. The aim is to explore the particular situation in Ireland with regard to ticks and TBD’s and to provide a reference for future workers in the field.

Emergence of tick-borne pathogens (Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Ricketsia raoultii and Babesia microti) in the Kyiv urban parks, Ukraine

To date, only limited data about the presence of ticks and circulation of tick-borne pathogens in urban parks of Kyiv in northern Ukraine are available. In total, 767 ticks (696 Ixodes ricinus and 69 Dermacentor reticulatus) collected in seven urban parks and one suburban oak wood park in Kyiv were individually analyzed by the PCR assays. Tick-borne pathogens, namely spirochetes from Borrelia burgdorferi sensu lato complex, Anaplasma phagocytophilum, and Babesia microti, were detected in 11.1% of tested I. ricinus ticks. In total, 4% of I. ricinus ticks tested positive for the presence of B. burdorferi s.l. (Borrelia afzelii and Borrelia garinii), 5.2% for A. phagocytophilum, and Ba. microti was confirmed in 1.9% of examined ticks. Mixed infections were recorded in four DNA samples, representing the prevalence of 0.6%. One female and two I. ricinus nymphs were simultaneously infected with B. afzelii and A. phagocytophilum, and one female carried B. afzelii and Ba. microti. In addition, 10.1% of D. reticulatus ticks tested positive for Rickettsia raoultii. Identification of infectious agents and their diversity, assessment of the relative epidemiological importance and determination of the prevalence in questing ticks from central parts of the cities are crucial steps towards the tick-borne diseases surveillance in urban environment.

Molecular Detection of Tick-Borne Pathogens in Humans with Tick Bites and Erythema Migrans, in the Netherlands

BACKGROUND

Tick-borne diseases are the most prevalent vector-borne diseases in Europe. Knowledge on the incidence and clinical presentation of other tick-borne diseases than Lyme borreliosis and tick-borne encephalitis is minimal, despite the high human exposure to these pathogens through tick bites. Using molecular detection techniques, the frequency of tick-borne infections after exposure through tick bites was estimated.

METHODS

Ticks, blood samples and questionnaires on health status were collected from patients that visited their general practitioner with a tick bite or erythema migrans in 2007 and 2008. The presence of several tick-borne pathogens in 314 ticks and 626 blood samples of this cohort were analyzed using PCR-based methods. Using multivariate logistic regression, associations were explored between pathogens detected in blood and self-reported symptoms at enrolment and during a three-month follow-up period.

RESULTS

Half of the ticks removed from humans tested positive for Borrelia burgdorferi sensu lato, Anaplasma phagocytophilum, Candidatus Neoehrlichia mikurensis, Rickettsia helvetica, Rickettsia monacensis, Borrelia miyamotoi and several Babesia species. Among 92 Borrelia burgdorferi s. l. positive ticks, 33% carried another pathogen from a different genus. In blood of sixteen out of 626 persons with tick bites or erythema migrans, DNA was detected from Candidatus Neoehrlichia mikurensis (n = 7), Anaplasma phagocytophilum (n = 5), Babesia divergens (n = 3), Borrelia miyamotoi (n = 1) and Borrelia burgdorferi s. l. (n = 1). None of these sixteen individuals reported any overt symptoms that would indicate a corresponding illness during the three-month follow-up period. No associations were found between the presence of pathogen DNA in blood and; self-reported symptoms, with pathogen DNA in the corresponding ticks (n = 8), reported tick attachment duration, tick engorgement, or antibiotic treatment at enrolment.

CONCLUSIONS

Based on molecular detection techniques, the probability of infection with a tick-borne pathogen other than Lyme spirochetes after a tick bite is roughly 2.4%, in the Netherlands. Similarly, among patients with erythema migrans, the probability of a co-infection with another tick-borne pathogen is approximately 2.7%. How often these infections cause disease symptoms or to what extend co-infections affect the course of Lyme borreliosis needs further investigations.

Seroprevalence of seven pathogens transmitted by the Ixodes ricinus tick in forestry workers in France

In order to assess the level of occupational exposure to the main pathogens transmitted by the Ixodes ricinus tick, a seroprevalence study was performed on serum samples collected in 2003 from 2975 forestry workers of northeastern France. The global seroprevalence estimated for the seven pathogens studied was 14.1% (419/2975) for Borrelia burgdorferi sl, 5.7% (164/2908) for Francisella tularensis, 2.3% (68/2941) for tick-borne encephalitis virus, 1.7% (50/2908) for Anaplasma phagocytophilum and 1.7% (48/2908) for Bartonella henselae. The seroprevalences of Babesia divergens and Babesia microti studied in a subgroup of participants seropositive for at least one of these latter pathogens were 0.1% (1/810) and 2.5% (20/810), respectively. Borrelia burgdorferi sl seroprevalence was significantly higher in Alsace and Lorraine and F. tularensis seroprevalence was significantly higher in Champagne-Ardenne and Franche-Comté. The results of this survey also suggest low rates of transmission of Bartonella henselae and F. tularensis by ticks and a different west/east distribution of Babesia species in France. The frequency and potential severity of these diseases justify continued promotion of methods of prevention of I. ricinus bites.

Infection with Babesia microti in humans with non-specific symptoms in North East Poland

AIM

The aim of the study was to evaluate the clinical course and effectiveness of diagnostics tools for Babesia spp. infection in patients bitten by ticks.

MATERIALS AND METHODS

Five hundred and forty-eight patients hospitalised or seen in outpatients department because of various symptoms after a tick bite were included in the study. PCR, nucleotide sequencing of Babesia 18S rRNA gene fragment, blood smears and serological tests for Babesia spp., TBEV, A. phagocytophilum and B. burgdorferi were performed in all patients. Six patients infected with Babesia were included in the final analysis. They had PCR, Babesia 18S rRNA gene fragment nucleotide sequencing, blood smears and serological tests for Babesia spp., TBEV, A. phagocytophilum and B. burgdorferi performed twice.

RESULTS

Tick-borne infection with Babesia microti in six immunocompetent patients with non-specific symptoms was confirmed for the first time in Poland. No severe course of the disease was seen. No piroplasm forms were noticed within erythrocytes on blood smear. Three patients developed a serological response.

CONCLUSIONS

Immunocompetent patients may be unaware of infection with Babesia microti after a tick bite. It must be included in the differential diagnosis after the tick bite. In patients with low parasitaemia PCR and serology seem useful when blood smear is negative. Self-elimination of Babesia spp. is possible, especially in cases with low parasitaemia.

Babesia in a Nonsplenectomized Patient Requiring Exchange Transfusion

Babesiosis is a tick born zoonosis caused by red blood cell parasites of the genus Babesia. It is caused predominantly by B. microti and B. divergens, microti being more common in the US. The parasites are transmitted by Ixodes tick to their host but infection can also spread by blood transfusion and perinatally. Clinical manifestations vary from subclinical infection to fulminating disease depending upon the immune status of the patient. About half of patients, hospitalized with babesiosis, develop complication with fatality rates of 6 to 9% which increase up to 21% among those with immunosuppression. A case of 58-year-old previously healthy man, infected by B. microti, was reported on 2000 who presented with severe disease characterized by severe anemia, DIC, and renal and respiratory failure. First case of overwhelming septic shock without respiratory involvement due to babesiosis in a healthy patient with an intact spleen was published in a case report on 2011. Since our patient here is an immunocompetent healthy male with intact spleen presenting with severe babesiosis requiring exchange transfusion, this presentation of Babesia is rare and warrants further study.

Broad-range survey of tick-borne pathogens in Southern Germany reveals a high prevalence of Babesia microti and a diversity of other tick-borne pathogens

Abstract Ticks harbor numerous pathogens of significance to human and animal health. A better understanding of the pathogens carried by ticks in a given geographic area can alert health care providers of specific health risks leading to better diagnosis and treatments. In this study, we tested 226 Ixodes ricinis ticks from Southern Germany using a broad-range PCR and electrospray ionization mass spectrometry assay (PCR/ESI-MS) designed to identify tick-borne bacterial and protozoan pathogens in a single test. We found 21.2% of the ticks tested carried Borrelia burgdorferi sensu lato consisting of diverse genospecies; a surprisingly high percentage of ticks were infected with Babesia microti (3.5%). Other organisms found included Borrelia miyamotoi, Rickettsia helvetica, Rickettsia monacensis, and Anaplasma phagocytophilum. Of further significance was our finding that more than 7% of ticks were infected with more than one pathogen or putative pathogen.

Babesia spp. in questing ticks from eastern Poland: prevalence and species diversity

A total of 853 questing Ixodes ricinus males, females, and nymphs and of 582 questing Dermacentor reticulatus males and females were collected from vegetation on the territory of the Lublin province (eastern Poland). The ticks were examined for the presence of Babesia by PCR detecting part of 18S ribosomal RNA (rRNA) gene and nuclear small subunit rRNA (SS-rDNA) for determining of Babesia spp. and Babesia microti, respectively. The overall incidence of Babesia strains in I. ricinus ticks was 4.6 %. Three species of Babesia were identified. The prevalent species was B. microti which occurred in 2.8 % of ticks, while Babesia venatorum, Babesia divergens, and unidentified Babesia species were found at the frequency of 1.2, 0.2, and 0.3 %, respectively. Altogether, B. microti constituted 61.5 % of the total strains detected in I. ricinus, B. venatorum—25.7 %, B. divergens—5.1 %, and unidentified Babesia species—7.7 %. The prevalence of Babesia species in I. ricinus did not depend significantly on locality (χ² = 1.885, P = 0.390) nor on the tick stage (χ² = 4.874, P = 0.087). The incidence of Babesia strains in D. reticulatus ticks was 2.7 %. Two species of Babesia were identified. Again, the prevalent species was B. microti which occurred in 2.1 % of ticks, while B. canis was found in 0.7 % of ticks. In one D. reticulatus female, B. canis and B. microti co-infection was found. Altogether, B. microti constituted 75 % of the total strains detected in D. reticulatus while B. canis formed 25 % of the total strains. The frequency of the occurrence of Babesia species in D. reticulatus did not depend significantly on locality (χ² = 0.463, P = 0.793). The difference between the prevalence of Babesia in males and females of D. reticulatus was insignificant (P = 0.0954); nymphs were not found. The dominance of B. microti in the species composition of tick-borne Babesia found in this study was typical for eastern Europe. In conclusion, the results revealed that the population inhabiting the forested area of eastern Poland could be exposed to Babesia parasites, especially to those from the species B. microti, by a bite of I. ricinus, a competent vector of human babesiosis, and probably also by a bite of D. reticulatus whose role in the transmission of human babesiosis needs to be clarified.