Babesia ovis as the main causative agent of sheep babesiosis in Iran

Babesia ovis secreted antigen-1 is a diagnostic marker during the active Babesia ovis infections in sheep

Ovine babesiosis caused by Babesia ovis is an economically significant disease. Recently, a few B. ovis-specific proteins, including recombinant B. ovis secreted antigen-1 (rBoSA1), have been identified. Immunological analyses revealed that rBoSA1 resides within the cytoplasm of infected erythrocytes and exhibits robust antigenic properties for detecting anti-B. ovis antibodies. This protein is released into the bloodstream during the parasite's development. It would be possible to diagnose active infections by detecting this secretory protein. For this purpose, a rBoSA1-specific polyclonal antibody-based sandwich ELISA was optimized in this study. Blood samples taken from the naturally (n: 100) and experimentally (n: 15) infected sheep were analyzed for the presence of native BoSA1. The results showed that native BoSA1 was detectable in 98% of naturally infected animals. There was a positive correlation between parasitemia level in microscopy and protein density in sandwich ELISA. Experimentally infected animals showed positive reactions from the first or second day of inoculations. However, experimental infections carried out by Rhipicephalus bursa ticks revealed the native BoSA1 was detectable from the 7th day of tick attachment when the parasite began to be seen microscopically. Sandwich ELISA was sensitive enough to detect rBoSA1 protein at a 1.52 ng/ml concentration. Additionally, no serological cross-reactivity was observed between animals infected with various piroplasm species, including Babesia bovis, B. bigemina, B. caballi, B. canis, B. gibsoni, Theileria equi, and T. annulata. Taken collectively, the findings show that the rBoSA1-specific polyclonal antibody-based sandwich ELISA can be successfully used to diagnose clinical B. ovis infections in sheep at the early stage.

Whole genome sequence and diversity in multigene families of Babesia ovis

Ovine babesiosis, caused by Babesia ovis, is an acute, lethal, and endemic disease worldwide and causes a huge economic loss to animal industry. Pathogen genome sequences can be utilized for selecting diagnostic markers, drug targets, and antigens for vaccine development; however, those for B. ovis have not been available so far. In this study, we obtained a draft genome sequence for B. ovis isolated from an infected sheep in Turkey. The genome size was 7.81 Mbp with 3,419 protein-coding genes. It consisted of 41 contigs, and the N50 was 526 Kbp. There were 259 orthologs identified among eight Babesia spp., Plasmodium falciparum, and Toxoplasma gondii. A phylogeny was estimated on the basis of the orthologs, which showed B. ovis to be closest to B. bovis. There were 43 ves genes identified using hmm model as well. They formed a discriminating cluster to other ves multigene family of Babesia spp. but showed certain similarities to those of B. bovis, B. caballi, and Babesia sp. Xinjiang, which is consistent with the phylogeny. Comparative genomics among B. ovis and B. bovis elucidated uniquely evolved genes in these species, which may account for the adaptation.

Anaemia in Sheep Caused by Babesia and Theileria Haemoparasites

Piroplasmoses in sheep are caused by vector-borne apicomplexan protozoa, Babesia and Theileria. Different species are responsible for the disease; some species are more pathogenic than others and have a worldwide distribution. In this sense, these causative agents can cause anaemia in flocks. In general, these vector-borne diseases infect small ruminants and cause host-mediated pathology. In the case of Babesia species, a combination of different mechanisms is involved: red blood cell lysis due to intracellular parasite multiplication, activation of biogenic amines and the coagulation system with the possibility of disseminated intravascular coagulation. By contrast, less information is available on the different immunopathogenic mechanisms involved in the development of anaemia in sheep with theileriosis. However, the mechanisms of pathogenic action in theileriosis are similar to those studied in babesiosis. Diagnosis is based on compatible clinical signs, laboratory findings, specific diagnostic tests and the presence of the tick vector. Some of these tests detect the causative agent itself, such as direct identification by light microscopy and molecular analysis. In contrast, other tests detect the sheep's immune response to the organism by serology. Both diseases pose a significant diagnostic challenge for veterinary practitioners around the world. This review presents the most frequent clinical signs, pathogenesis and clinicopathological findings, diagnosis.

Identification of Theileria spp. in sheep and goats from Jeddah, Saudi Arabia, using molecular techniques

Background

Thileriosis is a tick -born disease caused by hemoprotozoan parasites which has global veterinary and economic implications.

Methods

Blood samples were collected from 216 sheep and 83 goats from Jeddah, Saudi Arabia, were analyzed to determine whether the animals were infected with Theileria spp. parasites. The parasites were detected using a polymerase chain reaction (PCR) targeting the gene of 18S rRNA followed by sequencing.

Results

According to obtained findings, Theileria spp. were detected in sheep (57.8%, 48/83) and goats (51.9%, 112/216). Phylogenetic analysis to sequence data showed that T. ovis identified in this study were found to be closely connected to an isolate from Turkey, with 84.4–99.8% pairwise identity and 52.35–99.79% coverage.

Hyalomma spp. ticks and associated Anaplasma spp. and Ehrlichia spp. on the Iran-Pakistan border

Background

Anaplasmosis and ehrlichiosis are tick-borne diseases affecting humans and livestock, particularly in tropical and subtropical regions. Animal husbandry is the main activity of people on the borders of Iran and Pakistan, with thousands of cattle crossing the border each week.

Methods

PCR and sequencing of the 16S rRNA gene was used to determine the percentage and geographical distribution of the pathogens carried by Hyalomma spp. (n = 306) collected from 126 goats, cattle and camels in the region between November 2017 and late March 2018.

Results

In total, 1124 hard ticks including 1020 Hyalomma spp. ticks belonging to six species (Hyalomma anatolicum, Hyalomma asiaticum, Hyalomma marginatum, Hyalomma dromedarii, Hyalomma schulzei, and Hyalomma detritum) were found on the borders of Iran and Pakistan, with H. anatolicum being the most prevalent tick species. Anaplasma spp. and/or Ehrlichia spp. DNA was found in 68.3% of the engorged tick specimens (n = 256). Sequencing of a subset (12.6%) of PCR-positive samples revealed Anaplasma ovis, Anaplasma marginale, and Ehrlichia ewingii DNA in 81.8%, 9.1%, and 9.1% of the ticks, respectively. To our knowledge, this is the first report of E. ewingii, an important human pathogen, in Iran.

Conclusions

Based on molecular analysis, three pathogenic Anaplasmataceae were detected in six Hyalomma spp. parasitizing cattle, goats and camels, confirming the presence of these pathogens along the Iran-Pakistan border.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04956-3.

Development of a novel multiplex PCR assay for the detection and differentiation of Plasmodium caprae from Theileria luwenshuni and Babesia spp. in goats

Intraerythrocytic parasites are traditionally identified by the microscopic examination of Giemsa-stained blood smears. However, this method does not always allow for the identification of individual species in goat's RBCs. Moreover, its unreliability in detecting low levels of parasitemia makes it unsuitable for epidemiological investigations and leaves goat farms vulnerable to potential outbreaks. In the present study, a novel multiplex PCR (mPCR) targeting the cytochrome c oxidase subunit I (COI) gene was developed to detect and subsequently differentiate Plasmodium caprae, Theileria luwenshuni, and Babesia spp. The specificity of each primer set was assessed both in silico and with a panel of DNA samples from the hosts themselves and other goat hemoparasites. Amplicons generated from each pair of primers were 664, 555, and 320-bp for P. caprae, Babesia spp., and T. luwenshuni, respectively. These products were further confirmed by sequencing. Our novel mPCR reactions successfully demonstrated the accurate and simultaneous amplification of the three parasites' DNA samples. The current mPCR method showed no cross-amplification with unintended targets. The detection limit of the mPCR in this study was 10⁸ parasites' DNA copies per reaction. The current mPCR was able to detect the minimum parasitemia of approximately 0.001%, 0.000005%, 0.00001% for P. caprae, Babesia spp. and T. luwenshuni, respectively. The diagnostic specificity in the detection of P. caprae and T. luwenshuni ranged from 94.9 to 100 %. The mPCR was further applied to a collection of field blood samples from five provinces in Thailand to validate its reliability and applicability. The results demonstrated the successful detection of P. caprae, Babesia spp. and T. luwenshuni in goat samples with the same sensitivity levels as conventional PCR methods. This study also confirmed the presence of T. luwenshuni and Babesia spp. in Thai goats. The current mPCR method offers an alternative for the diagnosis of P. caprae, T. luwenshuni, and Babesia spp., either single or under co-infection conditions, and for large-scale surveillance.

An integrated overview of the bacterial flora composition of Hyalomma anatolicum, the main vector of CCHF

The microbial flora associated with Hyalomma anatolicum ticks was investigated using culture-dependent (CD) and independent (next generation sequencing, NGS) methods. The bacterial profiles of different organs, development stages, sexes, and of host cattle skins were analyzed using the CD method. The egg and female gut microbiota were investigated using NGS. Fourteen distinct bacterial strains were identified using the CD method, of which Bacillus subtilis predominated in eggs, larval guts and in adult female and male guts, suggesting probable transovarial transmission. Bacillus velezensis and B. subtilis were identified in cattle skin and tick samples, suggesting that skin is the origin of tick bacteria. H.anatolicum males harbour lower bacterial diversity and composition than females. The NGS analysis revealed five different bacterial phyla across all samples, Proteobacteria contributing to >95% of the bacteria. In all, 56611sequences were generated representing 6,023 OTUs per female gut and 421 OTUs per egg. Francisellaceae family and Francisella make up the vast majority of the OTUs. Our findings are consistent with interference between Francisella and Rickettsia. The CD method identified bacteria, such B. subtilis that are candidates for vector control intervention approaches such paratransgenesis whereas NGS revealed high Francisella spp. prevalence, indicating that integrated methods are more accurate to characterize microbial community and diversity.

Primary Tick-Borne Protozoan and Rickettsial Infections of Animals in Turkey

Parasitic diseases caused by ticks constitute a barrier on global animal production, mainly in tropical and subtropical regions. As a country with a temperate and subtropical climate, Turkey has topography, climate, and pasture resources, and these resources are suitable for animal breeding and parasite–host–vector relationships throughout the country. This geography restricts the regulations on animal movements in the southeastern and eastern Anatolia because of the close contact with the neighboring states. The livestock resources in Turkey are regulated by strong foundations. Almost 30% of the agriculture-based gross domestic product is provided by the livestock industry. Parasitic diseases arising from ticks are endemic in Turkey, and they have a significant impact on the economy and animal health, particularly for ruminants. The main and economically-important tick-borne diseases (TBDs) suffered by animals include theileriosis, babesiosis, hepatozoonosis, and cytauxzoonosis caused by protozoa, and anaplasmosis and ehrlichiosis caused by rickettsiae. The most common hemoprotozoan and rickettsial agents are Anaplasma marginale, Anaplasma ovis, Anaplasma phagocytophilum, Anaplasma platys, Babesia bigemina, Babesia caballi, Babesia ovis, Cytauxzoon felis, Ehrlichia canis, Hepatozoon canis, Theileria annulata and Theileria equi. These diseases are basically controlled through treatment and measures for tick control. Vaccination can be performed for only tropical theileriosis caused in Turkey. We reviewed the studies published in domestic and international journals to gather epidemiological data regarding the major TBDs suffered by animals in Turkey.

Ticks and Tick-Borne Diseases of Livestock in the Middle East and North Africa: A Review

Ticks are important vectors of an array of viral, bacterial and protozoan pathogens resulting in a wide range of animal and human diseases. There is limited information in the literature about tick species in the Middle East and North Africa (MENA) countries, even though they have suitable climate and vegetation for ticks and their hosts. We reviewed the occurrence of tick species and the pathogens they transmit from the MENA on published papers from 1901-2020. We found taxonomic records of 55 tick species infesting livestock representing the following eight genera: Ornithodoros, Otobius, Amblyomma, Dermacentor, Haemaphysalis, Hyalomma, Ixodes, and Rhipicephalus. In addition, 15 pathogens were recorded causing diseases of significance, with Crimean-Congo hemorrhagic fever, theileriosis, babesiosis and anaplasmosis being widely distributed diseases in the region. In recent decades, there has been increasing trends in disease occurrence and movement associated with global movement of humans and global trade of animals. We suggest that disease control and prevention could be achieved effectively through good integration between public health, veterinary medicine and animal management, and ecological approaches. We recommend further research in the areas of tick ecology and tick born-disease transmission. Furthermore, we suggest evaluation and improvement of disease control policies in the region.

First Molecular Detection of Babesia ovis, Theileria spp., Anaplasma spp., and Ehrlichia ruminantium in Goats from Western Uganda

Ticks and tick-borne diseases are major impediments to livestock production. To date, there have been several studies on the prevalence of tick-borne pathogens (TBPs) in cattle, but very few studies have documented TBPs in goats in Uganda. In this study, polymerase chain reaction assays and sequence analysis of different molecular markers were used to assess the presence and genetic characteristics of TBPs in 201 goats from Kasese district in western Uganda. The risk factors associated with TBP infections were also analyzed. We detected Theileria spp. (13.4%), Anaplasma phagocytophilum (10.9%), Anaplasma ovis (5.5%), Babesia ovis (5.5%), and Ehrlichia ruminantium (0.5%). The sequences of B. ovis ssu rRNA and A. ovismsp4 genes showed some degree of diversity among the parasite isolates in this study. The E. ruminantium pCS20 sequence formed a well-supported clade with isolates from Amblyomma variegatum ticks from Uganda. Wildlife interaction, sampling location, low body condition score, tick infestation, and herd size were significantly associated with TBP infections in the goats. The findings in this study provide important information on the epidemiology of tick-borne pathogens in Uganda, and show that goats could be potential reservoirs for tick-borne pathogens.

Quantitative Proteomics Identifies Metabolic Pathways Affected by Babesia Infection and Blood Feeding in the Sialoproteome of the Vector Rhipicephalus bursa

The negative impact of ticks and tick-borne diseases on animals and human health is driving research to discover novel targets affecting both vectors and pathogens. The salivary glands are involved in feeding and pathogen transmission, thus are considered as a compelling target to focus research. In this study, proteomics approach was used to characterize Rhipicephalusbursa sialoproteome in response to Babesiaovis infection and blood feeding. Two potential tick protective antigens were identified and its influence in tick biological parameters and pathogen infection was evaluated. Results demonstrate that the R. bursa sialoproteome is highly affected by feeding but infection is well tolerated by tick cells. The combination of both stimuli shifts the previous scenario and a more evident pathogen manipulation can be suggested. Knockdown of ub2n led to a significative increase of infection in tick salivary glands but a brusque decrease in the progeny, revealing its importance in the cellular response to pathogen infection, which is worth pursuing in future studies. Additionally, an impact in the recovery rate of adults (62%), the egg production efficiency (45.75%), and the hatching rate (88.57 %) was detected. Building knowledge on vector and/or pathogen interplay bridges the identification of protective antigens and the development of novel control strategies.

Transient transfection of Babesia ovis using heterologous promoters

Babesia species, etiological agents of babesiosis, a recognized emerging tick-borne disease, are a significant animal and human health concern with a worldwide socio-economic impact. The development of genetic manipulation techniques, such as transfection technology, is pivotal to improve knowledge regarding the biology of these poorly studied parasites towards better disease control strategies. For Babesia ovis, responsible for ovine babesiosis, a tick-borne disease of small ruminants, these tools are not yet available. The present study was based on the existence of interchangeable cross-species functional promoters between Babesia species. Herein, we describe for the first time B. ovis transient transfection using two heterologous promoters, the ef-1α-B intergenic regions from B. bovis and B. ovata. Their ability to drive expression of a reporter luciferase in B. ovis supports their cross-species functionality. Also, the ef-1α-B promoter region from B. ovata resulted in statistically significantly higher luminescence values in comparison to the control, thus a possibly suitable promoter for stable gene expression. Evaluation of transfection efficiency using qPCR demonstrated that higher luminescence levels were due to promoter strength rather than a higher transfection efficiency. These findings represent a step forward in the development of methods for B. ovis genetic manipulation, an undoubtedly necessary tool to study this parasite basic biology, including its life cycle, the parasite interactions with host cells and virulence factors.

Comparison of protectiveness of recombinant Babesia ovis apical membrane antigen 1 and B. ovis-infected cell line as vaccines against ovine babesiosis

Babesiosis is a disease complex caused by unicellular Babesia parasites and among them, malignant ovine babesiosis caused by B. ovis has a devastating economical impact on the small ruminant industry. The control of disease is mainly based on chemotherapy and preventing animals from tick infestation and to date no vaccine is available against ovine babesiosis. The requirement for vaccination against B. ovis infection in endemically unstable regions is necessary for implementation of effective disease control measures. The aim of the present study was to evaluate the effectiveness of different immunisation protocols against disease in sheep experimentally vaccinated with recombinant B. ovis apical membrane antigen-1 (rBoAMA-1) and/or live, a B. ovis-infected cell line. Sheep were divided into four experimental groups, plus a control group. Animals were immunised either with the B. ovis stabilate, or with rBoAMA-1, or with both rBoAMA-1 and the B. ovis stabilate. Western blots and ELISAs indicated that immunisation with rBoAMA-1 resulted in generation of a specific response against the recombinant protein, but the degree of antibody response did not correlate with the level of induced protection against challenge. The strongest immune response was induced in animals co-immunised with the live B. ovis stabilate plus rBoAMA-1. Both the hematological and parasitological findings indicated that this co-immunisation regimen has vaccine potential to limit losses incurred by ovine babesiosis in endemic countries.

High genetic diversity and differentiation of the Babesia ovis population in Turkey

Babesia ovis is a tick-transmitted protozoan haemoparasite causing ovine babesiosis in sheep and goats leading to considerable economic loss in Turkey and neighbouring countries. There are no vaccines available, therapeutic drugs leave toxic residues in meat and milk, and tick vector control entails environmental risks. A panel of eight mini- and micro-satellite marker loci was developed and applied to study genetic diversity and substructuring of B. ovis from western, central and eastern Turkey. A high genetic diversity (H_e  = 0.799) was found for the sample of overall B. ovis population (n = 107) analyzed. Principle component analysis (PCoA) revealed the existence of three parasite subpopulations: (a) a small subpopulation of isolates from Aydin, western Turkey; (b) a second cluster predominantly generated by isolates from western Turkey; and (c) a third cluster predominantly formed by isolates from central and eastern Turkey. Two B. ovis isolates from Israel included in the analysis clustered with isolates from central and eastern Turkey. This finding strongly suggests substructuring of a major Turkish population into western versus central-eastern subpopulations, while the additional smaller B. ovis population found in Aydin could have been introduced, more recently, to Turkey. STRUCTURE analysis suggests a limited exchange of parasite strains between the western and the central-eastern regions and vice versa, possibly due to limited trading of sheep. Importantly, evidence for recombinant genotypes was obtained in regionally interchanged parasite isolates. Important climatic differences between the western and the central/eastern region, with average yearly temperatures of 21°C versus 15°C, correspond with the identified geographical substructuring. We hypothesize that the different climatic conditions may result in variation in the activity of subpopulations of Rhipicephalus spp. tick vectors, which, in turn, could selectively maintain and transmit different parasite populations. These findings may have important implications for vaccine development and the spread of drug resistance.

Molecular Characterization and Phylogenetic Analysis of Theileria spp. and Babesia spp. Isolated from Various Ticks in Southeastern and Northwestern Regions of Iran

INTRODUCTION

Piroplasms are hemoprotozoa comprising heterogeneous tick-borne parasites, which are differentiated into three genera, namely Babesia, Theileria, and Cytauxzoon. The aim of this study was to determine the prevalence, molecular identification, and phylogenetic relationship of both Theileria spp. and Babesia spp. in tick species isolated from different domestic animals from two different geographical locations of Iran.

MATERIALS AND METHODS

A total of 930 ticks collected from goats, sheep, and cattle were examined for the presence of Theileria spp. and Babesia spp. using PCR targeting 18S rRNA gene followed by sequencing. Sequence analysis was performed based on the data published in the GenBank on Theileria spp. and Babesia spp. isolates using bioinformatic tools, such as the standard nucleotide BLAST.

RESULTS

A 390 or 430 base pair fragment of 18S rRNA gene of Theileria and Babesia species was successfully amplified in 17.2% of the examined ticks (16of 93). Genome of Theileria or Babesia species was detected in 4 ticks collected in Heris, including 3 Dermacentor marginatus and 1 Rhipicephalus sanguineus, and also in 12 ticks collected in Chabahar, including 10 R. sanguineus and 2 D. marginatus. Partial analysis of 18S rRNA gene sequence of the four D. marginatus, collected from goats and sheep in Heris, showed that they were infected with Theileria spp. that were 95-97% identical to Iranian Theileria ovis present in the GenBank database (GenBank acc. no. KP019206.1). While the five R. sanguineus, collected from sheep and goats in Chabahar, were infected with Babesia spp. that were 91-97% identical to Iranian Babesia ovis present in the GenBank database (GenBank acc. no. AY362829.1: KT587794.1).

CONCLUSION

The prevalence of Babesia and Theileria is different in southeastern and northwestern parts of Iran, with higher prevalence of babesiosis in the southeastern region and that of theileriosis in the northwestern region. Sequence analysis of 18S rRNA gene revealed that T. ovis and B. ovis are genetically polymorphic in these regions.

Rhipicephalus bursa Sialotranscriptomic Response to Blood Feeding and Babesia ovis Infection: Identification of Candidate Protective Antigens

Ticks are among the most prevalent blood-feeding arthropods, and they act as vectors and reservoirs for numerous pathogens. Sialotranscriptomic characterizations of tick responses to blood feeding and pathogen infections can offer new insights into the molecular interplay occurring at the tick-host-pathogen interface. In the present study, we aimed to identify and characterize Rhipicephalus bursa salivary gland (SG) genes that were differentially expressed in response to blood feeding and Babesia ovis infection. Our experimental approach consisted of RNA sequencing of SG from three different tick samples, fed-infected, fed-uninfected, and unfed-uninfected, for characterization and inter-comparison. Overall, 7,272 expressed sequence tags (ESTs) were constructed from unfed-uninfected, 13,819 ESTs from fed-uninfected, and 15,292 ESTs from fed-infected ticks. Two catalogs of transcripts that were differentially expressed in response to blood feeding and B. ovis infection were produced. Four genes coding for a putative vitellogenin-3, lachesin, a glycine rich protein, and a secreted cement protein were selected for RNA interference functional studies. A reduction of 92, 65, and 51% was observed in vitellogenin-3, secreted cement, and lachesin mRNA levels in SG, respectively. The vitellogenin-3 knockdown led to increased tick mortality, with 77% of ticks dying post-infestation. The reduction of the secreted cement protein-mRNA levels resulted in 46% of ticks being incapable of correctly attaching to the host and significantly lower female weights post-feeding in comparison to the control group. The lachesin knockdown resulted in a 70% reduction of the levels associated with B. ovis infection in R. bursa SG and 70% mortality. These results improved our understanding of the role of tick SG genes in Babesia infection/proliferation and tick feeding. Moreover, lachesin, vitellogenin-3, and secreted cement proteins were validated as candidate protective antigens for the development of novel tick and tick-borne disease control measures.

Semi-nested polymerase chain reaction-based detection of Babesia spp. in small ruminants from Northwest of Iran

Aim:

The present study aimed to detect Babesia ovis and Babesia motasi in the blood samples of sheep and goats from Northwest of Iran by the semi-nested polymerase chain reaction (PCR) technique.

Materials and Methods:

A total of 166 whole blood samples (including 123 sheep and 43 goats) were collected. In the first stage, the PCR was performed to amplify a piece of 18S rRNA gene of Babesia and Theileria genera. Then, semi-nested PCR was carried out on all PCR products to differentiate B. ovis and B. motasi.

Results:

The PCR indicated that totally, 19 (11.44%) out of 166 samples were positive for Babesia or Theileria spp. The semi-nested PCR showed that 38 samples (22.89%) were positive only for B. ovis. No significant association was found between the infection rate of B. ovis and age, gender and species of animals.

Conclusion:

In the present study, there was no evidence for B. motasi infection in small ruminants from Northwest of Iran. Therefore, B. ovis was the main causative agent of ovine Babesiosis in this region.

Deciphering Babesia-Vector Interactions

Understanding host-pathogen-tick interactions remains a vitally important issue that might be better understood by basic research focused on each of the dyad interplays. Pathogens gain access to either the vector or host during tick feeding when ticks are confronted with strong hemostatic, inflammatory and immune responses. A prominent example of this is the Babesia spp.—tick—vertebrate host relationship. Babesia spp. are intraerythrocytic apicomplexan organisms spread worldwide, with a complex life cycle. The presence of transovarial transmission in almost all the Babesia species is the main difference between their life cycle and that of other piroplasmida. With more than 100 species described so far, Babesia are the second most commonly found blood parasite of mammals after trypanosomes. The prevalence of Babesia spp. infection is increasing worldwide and is currently classified as an emerging zoonosis. Babesia microti and Babesia divergens are the most frequent etiological agents associated with human babesiosis in North America and Europe, respectively. Although the Babesia-tick system has been extensively researched, the currently available prophylactic and control methods are not efficient, and chemotherapeutic treatment is limited. Studying the molecular changes induced by the presence of Babesia in the vector will not only elucidate the strategies used by the protozoa to overcome mechanical and immune barriers, but will also contribute toward the discovery of important tick molecules that have a role in vector capacity. This review provides an overview of the identified molecules involved in Babesia-tick interactions, with an emphasis on the fundamentally important ones for pathogen acquisition and transmission.

Detection of Babesia infection among human, goats and sheep using microscopic and molecular methods in the city of Kuhdasht in Lorestan Province, West of Iran

Babesiosis is a lethal protozoan disease, responsible for the loss of livestock in Iran and in the world. The purpose of the current study was to detect and identify Babesia spp. infection using microscopic and molecular methods in human, sheep and goats in Kuhdasht region, in the Lorestan Province, west of Iran. During 2013, a total of 384 blood smear samples were collected from 51 goats, 306 sheep suspected of Babesiosis infection and 27 humans from Kuhdasht region. The blood samples were fixed, stained and under light microscopic examined. DNA samples were extracted and amplified by polymerase chain reaction of 18S-rRNA gene. PCR and the semi-nested PCR were performed to identify to Babesi spp. and to differentiate genus of Theileria and Babesia spp. The results of microscopic examination indicated that a total of 47 (12.2%) samples were positive for Babesia spp. infection: 38 (9.9%) belonging to sheep and 9 to goats (2.3%). No Babesia was observed in human samples. The PCR showed a band size of 389 bp, of Babesia spp. and the semi-nested PCR detected B. ovis with a band size of 186 bp. By molecular method, 16 (4.2%) sheep and 2 (0.5%) goat blood samples were infected by Babesia. Totally, 18 samples (4.7%) were observed to have Babesia, while no infection was found in human. Thus, the results of our study have shown sheep and goats could be vulnerable to Babesia spp., especially B. ovis in Lorestan Province, Iran. Therefore, studies on the status of the animal Piroplasmosis especially Theileriosis are recommended.

Prevalence of Theileria and Babesia species in Tunisian sheep

In this study, the prevalence of Theileria and Babesia species in sheep was assessed with Giemsa-stained blood smear examination and polymerase chain reaction to identify the different piroplasms in 270 sheep from three Tunisian bioclimatic zones (north, centre, and south). The overall infection prevalence by Babesia spp. and Theileria spp. in Giemsa-stained blood smears was 2.9% (8/270) and 4.8% (13/270) respectively. The molecular results showed that sheep were more often infected by Theileria ovis than Babesia ovis with an overall prevalence of 16.3% (44/270) and 7.8% (21/270) respectively (p = 0.01). The molecular prevalence by Babesia ovis was significantly higher in females than in males (p < 0.05). According to localities B. ovis was found exclusively in sheep from the centre of Tunisia (Kairouan) whereas Theileria ovis was found in all regions. Infections with T. ovis and B. ovis were confirmed by sequencing. The sequence of T. ovis in this study (accession numbers KM924442) falls into the same clade as T. ovis deposited in GenBank. The T. ovis amplicons (KM924442) showed 99%–100% identities with GenBank sequences. Moreover, comparison of the partial sequences of 18S rRNA gene of B. ovis described in this study (KP670199) revealed 99.4% similarity with B. ovis recently reported in northern Tunisia from sheep and goats. Three nucleotides were different at positions 73 (A/T), 417 (A/T), and 420 (G/T). It also had 99% identity with B. ovis from Spain, Turkey and Iraq. The results suggest a high T. ovis prevalence in Tunisia with a decreasing north-south gradient. This could be correlated to the vector tick distribution.

Development of a pan-Babesia FRET-qPCR and a survey of livestock from five Caribbean islands

Background

Babesia spp. are tick-borne protozoan hemoparasites and the second most common blood-borne parasites of mammals, in particular domestic animals. We used the Clustal Multiple Alignment program and 18S rRNA gene sequences of 22 Babesia species from GenBank to develop a PCR that could detect a wide variety of Babesia spp. in a single reaction. The pan-Babesia FRET-qPCR we developed reliably detected B. gibsoni, B. canis, B. vogeli, B. microti, B. bovis, and B. divergens under controlled conditions but did not react with closely related species, mainly Hepatozoon americanum, Theileria equi, and Toxoplasma gondii.

Results

When we tested the pan-Babesia FRET-qPCR on DNA of whole blood from 752 cattle, sheep, goats, donkeys and horses from five Caribbean islands, we detected Babesia spp. expected to be present in the animals, mainly B. bovis and B. bigemina in cattle and B. caballi in horses and donkeys. Further, we found that animals were not uncommonly infected with species of Babesia usually associated with other hosts, mainly B. vogeli and B. gibsoni in cattle, sheep and goats, B. rossi in goats, and B. caballi in goats and sheep. Finally, the pan-Babesia FRET-qPCR enabled us to identify unknown species of Babesia in cattle, goats, sheep and donkeys.

Conclusions

Overall, 70 % (525/752) of the animals we tested were positive confirming earlier limited studies that infections with Babesia spp. are common in livestock in the Caribbean.

A new immunoreactive recombinant protein designated as rBoSA2 from Babesia ovis: Its molecular characterization, subcellular localization and antibody recognition by infected sheep

Ovine babesiosis, caused by the intra-erythrocytic protozoan parasite Babesia ovis, is an infectious and economically important tick-borne disease of sheep. Diagnostic testing is an essential tool used for the control of the disease. In order to identify and characterize the immunoreactive proteins which are useful in serological diagnosis of the disease, a complementary DNA (cDNA) expression library was constructed from B. ovis merozoite mRNA. A cDNA clone designated as BoSA2 was identified by immunoscreening of a cDNA library using immune sheep serum. The sequence of the BoSA2 cDNA had a partial open reading frame of 1156 nucleotides encoding a polypeptide of 384 amino acid residues. Theoretical molecular mass for the mature protein was 43.5 kDa. The sequence of the BoSA2 was inserted into the expression vector pGEX-4T-1 and then expressed in Escherichia coli DH5α cells as a glutathione S-transferase (GST)-tagged fusion protein. This recombinant fusion protein (rBoSA2) was purified by GST-affinity chromatography. Immunoreactivity of the rBoSA2 was evaluated by indirect enzyme-linked immunosorbent assay (ELISA) using the sera from the animals naturally and experimentally infected with B. ovis. ELISA results demonstrated that this antigen was useful for the diagnosis of ovine babesiosis. The localization of the BoSA2 protein was shown in and on the parasite and in the cytoplasm of the infected erythrocyte by confocal laser microscope. To our knowledge, rBoSA2 is the second immunoreactive recombinant protein of B. ovis until the present.

Molecular detection of Babesia ovis in sheep and ticks using the gene encoding B. ovis surface protein D (BoSPD)

The gene encoding Babesia ovis surface protein D (BoSPD) was cloned from B. ovis cDNA library. This gene encodes a polypeptide chain of 155 amino acids, including a predicted 22 amino acid signal peptide. Sequence analysis of the BoSPD suggested that it is a surface protein with no known domains. BLAST analysis followed by multiple alignments showed four orthologs from other Apicomplexan species and suggested that BoSPD is specific for B. ovis. BoSPD-based PCR was then developed to specifically detect B. ovis in experimentally-infected sheep and Rhipicephalus bursa ticks, as well as in field samples. The PCR enabled detection of B. ovis at a calculated parasitemia of 0.0016% and was shown to be specific for B. ovis. Moreover, the BoSPD PCR allowed detection of prolonged subclinical infection in experimentally-infected lambs and in dissected organs of experimentally-infected ticks. Finally, the PCR was used to detect parasitemia in blood samples from naturally-infected sheep and in R. bursa ticks collected from sheep in an infected flock. These results suggest that the BoSPD gene sequence can be used as a specific and sensitive marker, allowing detection of subclinical parasitemia in sheep and in ticks. Based on its predicted properties, BoSPD may be considered as a candidate for anti-B. ovis vaccine development or a target for anti-B.ovis treatment.

Transmission of Babesia ovis by different Rhipicephalus bursa developmental stages and infected blood injection

In this report, the transmission efficacy of Babesia ovis, the principal causative agent of ovine babesiosis, was studied by infestation of lambs with different Rhipicephalus bursa stages or by injection of infected blood. Infected blood injection induced acute babesiosis in splenectomized lambs, while only mild clinical signs were observed in intact animals. Both splenectomized and intact lambs developed high antibody titer, detectable for at least 180 days post infection. Infestation of splenectomized and intact lambs with infected tick larvae did not induce clinical babesiosis or specific serum response in any of the examined animals. Similarly, infestation of one splenectomized lamb with partially-fed infected R. bursa males did not induce any clinical response or seroconversion. Nymph infestation caused a mild clinical response followed by specific seroconversion, in one out of five lambs. All animals infested with infected unfed adults (males and females) showed mild-to-severe clinical signs 8 to 12 days post infestation. The acute phase was followed by a marked seroconversion. Our results indicate that the principal transmission of B. ovis is performed by adult R. bursa ticks, and that the host reaction can last as long as 6 months following the acute infection.

Identification and expression of Babesia ovis secreted antigen 1 and evaluation of its diagnostic potential in an enzyme-linked immunosorbent assay

In order to identify immunoreactive proteins that are usable for the immunological diagnosis of Babesia ovis infections, a phage lambda cDNA expression library was constructed and screened using parasite-specific immune serum. Immunoscreening resulted in the identification of a full-length cDNA clone encoding a secreted protein designated Babesia ovis secreted antigen 1 (BoSA1). The full-length BoSA1 cDNA contained a 1,137-bp open reading frame that encoded a protein of 378 amino acids, with a signal peptide and 2 internal repeat domains. The theoretical molecular mass of the mature protein was 42.5 kDa. Recombinant BoSA1 (rBoSA1) protein was expressed in Escherichia coli strain DH5α cells as a glutathione S-transferase (GST) fusion protein and was purified by affinity chromatography. Purified rBoSA1 was tested for reactivity with sera from animals experimentally or naturally infected with B. ovis, in an indirect enzyme-linked immunosorbent assay (ELISA). The results showed that specific antibodies against rBoSA1 were detectable on days 7 and 8 of the experimental infection and were maintained during the sampling period. Additionally, 38 field sera taken from sheep naturally infected with B. ovis gave strong positive reactions in the ELISA between day 20 and day 30 of treatment. As a result, the identified recombinant BoSA1 protein seems to be a promising diagnostic antigen that is usable for the development of serological assays for the diagnosis of ovine babesiosis. This is the first report on the molecular cloning, expression, and potential use of a recombinant antigen for the diagnosis of ovine babesiosis.

Prevalence of piroplasms in small ruminants in North-West Tunisia and the first genetic characterisation of Babesia ovis in Africa

In this study, the prevalence of piroplasms in sheep and goats was assessed with Giemsa-stained blood smear examination, PCR and nested PCR-restriction fragment length polymorphism (RFLP) to identify Babesia and Theileria species, respectively, in 338 small ruminants (172 sheep and 166 goats) from three sites in North-West Tunisia during the 2011 summer season. The overall infection prevalence of piroplasms in Giemsa-stained blood smears was 3.2% (11/338), with a parasitaemia ranging from 0.01 to 0.05%. PCR detected two species, namely Babesia ovis (in sheep and goats) and Theileria ovis (in sheep), with an overall prevalence of 16.3%. The molecular prevalence of B. ovis was significantly higher in sheep than in goats (17.4% and 9%, respectively, p = 0.034). The same trend was observed for T. ovis in sheep and goats (5.8% and 0%, respectively, p = 0.004). Comparison of the partial sequences of the 18S ssu rRNA gene revealed 100% similarity amongst Babesia from sheep and goats. The single Theileria sequence in this study showed 100% similarity to T. ovis. A high similarity with all the blasted genotypes was reported for Theileria and Babesia sequences. This is the first molecular detection of B. ovis and genetic characterisation of small ruminants' piroplasms in Africa.

Determination of immunoreactive proteins of Babesia ovis

Babesia ovis, an intraerythrocytic protozoan parasite transmitted by ticks, causes severe infections in sheep in tropical and subtropical regions of the world. Parasite-specific immunoreactive proteins have been used as antigen in the serological diagnosis of babesiosis. There is no study about determination of B. ovis-specific proteins in sheep. This study was planned to determine the immunoreactive proteins of B. ovis. In this study, two splenectomized lambs, and twelve seropositive sheep and five seronegative lambs for anti-B. ovis antibodies were used as materials. Infected blood samples at 5% of parasitemia from the two splenectomized lambs experimentally infected with a virulent B. ovis field strain were analyzed for B. ovis-specific proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting (WB). B. ovis-specific five major proteins were recognized by anti-B. ovis serum but not by healthy sheep serum. They were of approximate molecular weights 154, 109, 77, 58, and 38 kDa. As the control samples, protein profiles of the blood extracts of two lambs before splenectomy operation were also blotted with the immune sera, but none of the five proteins was detected. These proteins were also immunoblotted with heterologous positive and negative sheep sera. All of twelve positive sera recognized the 109 kDa protein with 100 percent sensitivity. The 77 kDa protein reacted in 11 of 12 sera (91.6%). The sensitivities of the other 3 proteins ranged between 83.3% and 25%. The five protein bands immunoblotted with sera of the 5 negative lambs did not give any positive reaction. The results of this study revealed the presence of proteins recognized by the serum antibodies of experimentally and naturally infected sheep with B. ovis. Additional studies on the purification of these proteins and on subsequently their utilization in a serodiagnostic method are required to improve the serological diagnosis of ovine babesiosis.

Babesia: a world emerging

Babesia are tick-transmitted hemoprotozooans that infect mammals and birds, and which are acknowledged for their major impact on farm and pet animal health and associated economic costs worldwide. Additionally, Babesia infections of wildlife can be fatal if associated with stressful management practices; and human babesiosis, also transmitted by blood transfusion, is an increasing public-health concern. Due to the huge diversity of species reported to serve as Babesia hosts, all vertebrates might be potential carriers, as long as they are adequate hosts for Babesia-vector ticks. We here provide a comprehensive overview of the most relevant Babesia species, and a discussion of the classical taxonomic criteria. Babesia, Cytauxzoon and Theileria parasites are closely related and collectively referred to as piroplasmids. A possible scenario for the history of piroplasmids is presented in the context of recent findings, and its implications for future research avenues are outlined. Phylogenetic trees of all available 18S rRNA and hsp70 genes were generated, based on which we present a thoroughly revised molecular classification, comprising five monophyletic Babesia lineages, one Cytauxzoon clade, and one Theileria clade. Updated 18S rRNA and beta-tubulin gene trees of the B. microti isolates agree with those previously reported. To reconcile estimates of the origin of piroplasmids and ticks (~300 Ma, respectively), and mammalian radiation (60 Ma), we hypothesize that the dixenous piroplasmid life cycle evolved with the origin of ticks. Thus, the observed time gap between tick origin and mammalian radiation indicates the existence of hitherto unknown piroplasmid lineages and/or species in extant vertebrate taxa, including reptiles and possibly amphibians. The development and current status of the molecular taxonomy of Babesia, with emphasis on human-infecting species, is discussed. Finally, recent results from population genetic studies of Babesia parasites, and their implications for the development of pathogenicity, drug resistance and vaccines, are summarized.