Zoonotic babesiosis

Is babesiosis a rare zoonosis in Spain? Its impact on the Spanish Health System over 23 years

BACKGROUND

Babesiosis is a zoonosis caused by an intraerythrocytic protozoan of the genus Babesia and transmitted mainly by ticks of the Ixodes spp. complex. There is no comprehensive global incidence in the literature, although the United States, Europe and Asia are considered to be endemic areas. In Europe, the percentage of ticks infected with Babesia spp. ranges from 0.78% to 51.78%. The incidence of babesiosis in hospitalized patients in Spain is 2.35 cases per 10,000,000 inhabitants/year. The mortality rate is estimated to be approximately 9% in hospitalized patients but can reach 20% if the disease is transmitted by transfusion.

OBJECTIVE

To analyze the epidemiological impact of inpatients diagnosed with babesiosis on the National Health System (NHS) of Spain between 1997 and 2019.

METHODOLOGY

A retrospective longitudinal descriptive study that included inpatients diagnosed with babesiosis [ICD-9-CM code 088.82, ICD-10 code B60.0, cases ap2016-2019] in public Spanish NHS hospitals between 1 January 1997 and 31 December 2019 was developed. Data were obtained from the minimum basic dataset (CMBD in Spanish), which was provided by the Ministerio de Sanidad, Servicios Sociales e Igualdad after the receipt of a duly substantiated request and the signing of a confidentiality agreement.

MAIN FINDINGS

Twenty-nine inpatients diagnosed with babesiosis were identified in Spain between 1997 and 2019 (IR: 0.28 cases/10,000,000 person-years). A total of 82.8% of the cases were men from urban areas who were approximately 46 years old. The rate of primary diagnoses was 55.2% and the number of readmissions was 79.3%. The mean hospital stay was 20.3±19.2 days, with an estimated cost of €186,925.66. Two patients, both with secondary diagnoses of babesiosis, died in our study.

CONCLUSIONS

Human babesiosis is still a rare zoonosis in Spain, with an incidence rate that has been increasing over the years. Most cases occurred in middle-aged men from urban areas between summer and autumn. The Castilla-La-Mancha and Extremadura regions recorded the highest number of cases. Given the low rate of primary diagnoses (55.2%) and the high number of readmissions (79.3%), a low clinical suspicion is likely. There was a 6.9% mortality in our study. Both patients who died were patients with secondary diagnoses of the disease.

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.

Expression, Purification, and Biological Characterization of Babesia microti Apical Membrane Antigen 1

The intraerythrocytic apicomplexan Babesia microti, the primary causative agent of human babesiosis, is a major public health concern in the United States and elsewhere. Apicomplexans utilize a multiprotein complex that includes a type I membrane protein called apical membrane antigen 1 (AMA1) to invade host cells. We have isolated the full-length B. microti AMA1 (BmAMA1) gene and determined its nucleotide sequence, as well as the amino acid sequence of the AMA1 protein. This protein contains an N-terminal signal sequence, an extracellular region, a transmembrane region, and a short conserved cytoplasmic tail. It shows the same domain organization as the AMA1 orthologs from piroplasm, coccidian, and haemosporidian apicomplexans but differs from all other currently known piroplasmida, including other Babesia and Theileria species, in lacking two conserved cysteines in highly variable domain III of the extracellular region. Minimal polymorphism was detected in BmAMA1 gene sequences of parasite isolates from six babesiosis patients from Nantucket. Immunofluorescence microscopy studies showed that BmAMA1 is localized on the cell surface and cytoplasm near the apical end of the parasite. Native BmAMA1 from parasite lysate and refolded recombinant BmAMA1 (rBmAMA1) expressed in Escherichia coli reacted with a mouse anti-BmAMA1 antibody using Western blotting. In vitro binding studies showed that both native BmAMA1 and rBmAMA1 bind to human red blood cells (RBCs). This binding is trypsin and chymotrypsin treatment sensitive but neuraminidase independent. Incubation of B. microti parasites in human RBCs with a mouse anti-BmAMA1 antibody inhibited parasite growth by 80% in a 24-h assay. Based on its antigenically conserved nature and potential role in RBC invasion, BmAMA1 should be evaluated as a vaccine candidate.

First detection of Ixodes ricinus on beef cattle in Israel

This is the first report of the presence of Ixodes ricinus on beef cattle in Israel. Up to now, in the Middle East this tick was considered to be confined to Turkey and northern Iran. In the present study, tick samples collected from field-grazing beef cattle in western Galilee (northern Israel) were first examined morphologically for species-specific taxonomical features and then by molecular characterization. Ticks identified morphologically as I. ricinus were then examined by PCR with four different molecular markers: 12S rRNA, 16S rRNA, COX1 and cytochrome B. The PCR products were sequenced and compared with annotated I. ricinus sequences in GenBank™ and the analyzed sequences from the collected samples shared 98-99% identity with reported I. ricinus sequences. In contrast, sequences from the collected ticks shared identity of 91% or less with annotated sequences from other Ixodes species. Multiple alignments and neighbor-joining analyses performed for each of the four markers reinforced the results obtained from pairwise alignments. These findings demonstrated for the first time the presence in Israel of the tick species I. ricinus - with results confirmed by a combination of morphological examination and molecular analyses.

Molecular and Serological Evidence for Anaplasma platys and Babesia sp. Infection in a Dog, Imported in Belgium, from Southern Spain

This case report describes a dog suffering from a co-infection with Babesia and Anaplasma parasites. Anaplasma platys was found to be responsible for the anaplasmosis by molecular biology techniques, while microscopical and serological evidence was found for a coexistent babesiosis, although this could not be confirmed by polymerase chain reaction. Moreover, the possible risk of import of exotic pathogens is highlighted.

Potent antihematozoan activity of novel bisthiazolium drug T16: evidence for inhibition of phosphatidylcholine metabolism in erythrocytes infected with Babesia and Plasmodium spp

A leading bisthiazolium drug, T16, designed to mimic choline, was shown to exert potent antibabesial activity, with 50% inhibitory concentrations of 28 and 7 nM against Babesia divergens and B. canis, respectively. T16 accumulated inside Babesia-infected erythrocytes (cellular accumulation ratio, >60) by a saturable process with an apparent K(m) of 0.65 microM. Subcellular fractionation of Babesia parasites revealed the accumulation of T16 into a low-density fraction, while in malaria-infected erythrocytes a significant fraction of the drug was associated with heme malaria pigment. T16 exerts an early and specific inhibition of the de novo biosynthesis of phosphatidylcholine both in B. divergens- and Plasmodium falciparum-infected erythrocytes. Choline accumulation into isolated Babesia parasites was highly sensitive to inhibition by T16. These data are consistent with the hypothesis that bisthiazolium drugs target the de novo phosphatidylcholine biosynthesis of intraerythrocytic hematozoan parasites. In malaria parasites, which generate ferriprotoporphyrin IX during hemoglobin digestion, T16 binding to heme may enhance the accumulation and activity of the drug. The selectivity of accumulation and potent activity of this class of drug into parasite-infected erythrocytes offers unique advantages over more traditional antihematozoan drugs.

Evaluation of an indirect fluorescence immunoassay for the detection of serum antibodies against Babesia divergens in humans

Since an indirect fluorescence immunoassay (IFA) for the detection of specific antibodies against Babesia divergens in human sera is not commercially available, an in-house prepared B. divergens IFA for the examination of bovine sera was established for serological studies in humans. To determine whether the described IFA is appropriate for such studies, 2 B. divergens antigens (of human or bovine origin) were tested using serum samples obtained from febrile human patients with a history of 'tick bite'. Sera from other species of animals infected with B. divergens, Babesia EU1, B. microti or B. canis were also included for comparative purposes. All serum samples were also tested using a commercially available IFA for the detection of antibodies against B. microti, and the results compared with those obtained using blood smear and molecular techniques. This study showed that the evaluation and standardization of a B. divergens IFA for testing human sera is critical and that different B. divergens antigens provide different end-point titres of antibodies, leading to false negative or positive results. Serological cross-reactivity between B. divergens and Babesia EU1 needs to be taken into account when interpreting IFA results.

Epidemiology and ecology of TBE relevant to the production of effective vaccines

This review focuses on the epidemiology and ecology of the tick-borne encephalitis (TBE) virus including all the factors influencing the ecology of the TBE virus, environmental and climatic conditions, the vectors and reservoir hosts and their interactions. Consequently, the structure and the conditions of natural foci of TBE are described, as well. Special emphasis is given on data regarding the virus prevalence in ticks in the field. In the second part of this review all the epidemiological and surveillance data of TBE in the 27 European countries and in the Far East with risk areas of TBE and in China and Japan are summarised. Therefore the review is a basis for travellers and inhabitants to get background information for their personal risk assessment.