Twenty Years of Equine Piroplasmosis Research: Global Distribution, Molecular Diagnosis, and Phylogeny

Molecular prevalence and genotypic diversity of Theileria equi and Babesia caballi infecting horses in Kyrgyzstan

Equine piroplasmosis is caused by Theileria equi and Babesia caballi, which are hemoprotozoan parasites. Understanding the epidemiology and genotypes of T. equi and B. caballi is crucial for developing effective control strategies in endemic countries. However, the endemic status of these two parasite species remains uncertain in Kyrgyzstan due to lack of surveys. Our study, therefore, aimed to detect T. equi and B. caballi infections in Kyrgyzstan and identify their genotypes. Blood samples were collected from 226 horses across all seven provinces of Kyrgyzstan, namely Chuy, Issyk-Kul, Naryn, Talas, Jalal-Abad, Osh, and Batken. These blood samples were subjected to DNA extraction, followed by specific PCR assays targeting T. equi and B. caballi. We found that 56 (24.8%, confidence interval (CI): 19.6-30.8%) and 7 (3.1%, CI: 1.5-6.3%) of the tested horses were positive for T. equi and B. caballi infections, respectively. Theileria equi was detected in all surveyed provinces, whereas B. caballi was found in five provinces, except for Talas and Osh. Subsequent genotype-specific PCR assays showed that T. equi-positive horses harbored all five genotypes: A, B, C (also known as Theileria haneyi), D, and E. On the other hand, phylogenetic analysis of B. caballi rap-1 sequences detected the genotypes A and B1. The prevalence of T. equi and B. caballi suggests a potential risk of clinical equine piroplasmosis among horses in Kyrgyzstan, and the observed genotypic diversity underscores the challenges in managing the disease. Our findings emphasize the need for comprehensive control measures to effectively address equine piroplasmosis in Kyrgyzstan.

Development and Evaluation of a Semi-Nested PCR Method Based on the 18S ribosomal RNA Gene for the Detection of Babesia aktasi Infections in Goats

We developed and evaluated a semi-nested PCR assay for the detection of Babesia aktasi infection in goats based on the sequence of the B. aktasi 18S ribosomal RNA gene. Following in silico screening, the specificity of the primers was assessed using reference DNA samples, including B. ovis, B. motasi, B. crassa, B. venatorum, B. divergens, B. capreoli, Theileria ovis, and T. annulata. To determine the sensitivity of the method, blood infected with 2% parasitemia of B. aktasi was diluted to 10-fold serial dilutions. The method specifically amplified a 438 bp fragment of B. aktasi DNA, but did not demonstrate cross-amplification with the other hemoparasites tested. The sensitivity assay indicated that this PCR method was able to detect infection at a dilution of 10-8 of 2% parasitemia (0.074 parasites/200 µL). Ninety-seven blood samples collected from goats were used to analyze for B. aktasi, and the infection was detected in 18.5% of the goats. Additionally, the method was also applied to 44 field DNA samples that were detected to be positive for B. aktasi by reverse line blotting (RLB), and showed 84.1% agreement. The findings revealed that newly developed semi-nested PCR can detect B. aktasi infections in goats with high sensitivity and specificity.

New insights in the diagnosis and treatment of equine piroplasmosis: pitfalls, idiosyncrasies, and myths

Equine piroplasmosis (EP) is a global tick-borne disease of equids caused by the intraerythrocytic apicomplexan parasites Theileria equi and Babesia caballi, and the more recently discovered Theileria haneyi. These parasites can be transmitted by several tick species, including Dermacentor, Hyalomma, and Rhipicephalus, but iatrogenic and vertical transmission are also common. Clinical signs of EP include poor performance, fever, icterus, abortions, among others, and peracute or acute forms of infection are associated with high mortality in non-endemic areas. EP is a reportable disease and represents an important barrier for the international trade of horses and other equids, causing disruption of international equine sports. Tick control measures, serological and molecular diagnostic methods, and parasiticidal drugs are currently used against EP, while vaccines remain unavailable. Since most acaricides used in equids are non-environmentally friendly and linked to drug resistances, this is considered as an unsustainable approach. Imidocarb dipropionate (ID) and buparvaquone (BPQ) are currently the main drugs used to control the disease. However, while ID has several side and toxic effects and recurrent failures of treatment have been reported, BPQ is less effective in the clearance of T. equi infection and not available in some countries. Thus, novel alternative and effective therapeutics are needed. While current trade regulations require testing equids for EP before exportation, the lack of standardized PCR tests and limitations of the currently recommended serological assays entail a risk of inaccurate diagnosis. Hereby, we propose a combination of standardized PCR-based techniques and improved serological tests to diminish the risks of exporting EP-infected animals making equid international trade safer. In addition, this review discusses, based on scientific evidence, several idiosyncrasies, pitfalls and myths associated with EP, and identifies weaknesses of current methods of control and gaps of research, as initial steps toward developing novel strategies leading to control this disease.

The first study of the prevalence and genetic diversity of Theileria equi and Babesia caballi in horses in Russia

Equine piroplasmosis (EP) is a global worldwide infection, which can lead to the death of animals. Despite the causative agents of EP being well studied, there are no data on the distribution and genetic characteristics of EP agents in any region of Russia. In this study, blood samples from 750 horses from Novosibirsk province, Irkutsk province, and Altai region of Russian Siberia were examined for the presence of EP agents. Theileria equi and Babesia caballi were detected in all examined regions, with mean prevalence rates of 60.4% and 7.2%, respectively. The identified pathogens were genetically characterized by the 18S rRNA gene. The determined T. equi sequences were highly conserved and belonged to genotypes A and E, with genotype E being found in 88.6% of genotyped samples. In contrast to T. equi, B. caballi sequences were genetically diverse. Seven sequence variants of B. caballi were identified, and only two of them matched known sequences from the GenBank database. The determined B. caballi sequences belonged to four distinct branches within genotype A. Mixed infections with several variants of B. caballi or with T. equi and B. caballi were common. The conducted phylogenetic analysis based on all available B. caballi sequences of the 18S rRNA gene (> 900 bp) from GenBank and from this study first demonstrated the presence of five monophyletic clusters within genotype A and three clusters within genotype B. Thus, the genetic study of B. caballi from Siberia has significantly expanded the data on the genetic diversity of this pathogen.

Molecular detection and characterization of prevailing Theileria equi genotype in equine from northern India

Equine piroplasmosis caused by Theileria equi is a febrile, tick-borne disease of equids. However, there is limited literature about the genotyping of T. equi in India. Blood samples were collected from 202 horses and subjected to microscopy and PCR to detect T. equi. Initially, a universal screening primer pair targeting 18S ribosomal RNA genes common for Babesia caballi and T. equi was employed to amplify the DNA of both parasites. Thereafter additional primers were employed for species-specific detection resulting in amplification of approximately 435 bp specific for T. equi. T.equi was detected in 9.9% and 20.79% of horses screened by microscopy and PCR, respectively. The representative samples confirmed positive by PCR were sequenced, submitted to NCBI (OR651254, OR687254, OR685656, OR650830, OR650834), and used for genotype characterization and phylogenetic analysis. Employing Genetool and MEGA X software, the T. equi Indian isolates and across the globe were compared, and the results demonstrated 99.05-100% and 95.86-100% homologies, respectively. All the T. equi Indian isolates belonged to genotype A. Phylogeny based on the EMA-1 gene of five isolates (OR731831, OR731833, OR731829, OR731830, OR731832) were also characterized by sequencing and support the previous findings. Genotypes C and D, as well as genotypes B and E, exhibited lower levels of evolutionary divergence compared to other genotypes. The EMA-1 gene exhibited limited diversity and might not be the most suitable target for assessing variability within T. equi populations. The findings also reveal a significant association (p < 0.01) between T. equi infection and the presence of ticks.

Detection of tick-borne pathogens in Rhipicephalus bursa ticks collected from the autochthonous Garrano breed of horses in Portugal

The Garrano is a semi-feral horse breed native to several mountains in the northern Iberian Peninsula. Despite being endangered, this unique breed of pony has managed to survive in the wild and continues to be selectively bred, highlighting their remarkable resilience and adaptability to harsh environments. Wildlife plays a critical role in the survival of tick vectors in their natural habitats and the transfer of tick-borne pathogens, as they can serve as reservoir hosts for many agents and amplifiers for these vectors. The semi-feral lifestyle of the Garrano horses makes them particularly vulnerable to exposure to numerous tick species throughout the year. Therefore, the aim of this study was to investigate the occurrence of Anaplasma, Ehrlichia, Babesia, Theileria, and spotted fever rickettsiae in the Garrano horse ticks to obtain a knowledge of circulating agents in this host population. The collected ticks (n = 455) were identified as Rhipicephalus bursa. DNA specimens were organized in pools of 5 ticks, for molecular screening. Pools PCR results confirmed the presence of Candidatus Rickettsia barbariae (n = 12 for the ompB gene, n = 11 for the ompA gene and n = 6 for the gltA gene), Babesia bigemina (n = 1), Babesia caballi (n = 3), Theileria equi (n = 15) and Theileria haneyi (n = 1).These results confirm the circulation of an emerging rickettsial spotted fever group member, Candidatus R. barbariae, in R. bursa ticks. Our findings demonstrated that Candidatus R. barbariae co-circulates with B. bigemina and T. equi, which are vectored by R. bursa. We are reporting for the first time, the detection of T. haneyi among R. bursa ticks feeding in the Garrano horses in Portugal. Surveillance studies for tick-borne infections are essential to provide information that can facilitate the implementation of preventive and control strategies.

Expression of IL-10 and TGF-β1 in horses experimentally infected with T. equi merozoites is associated with antibody production but not modulation of pro-inflammatory responses

Theileria equi (T. equi) is an apicomplexan parasite that causes severe hemolytic anemia in equids. Presently, there is inadequate knowledge of the immune responses induced by T. equi in equid hosts impeding understanding of the host parasite relationship and development of potent vaccines for control of T. equi infections. The objective of this study was to evaluate the host-parasite dynamics between T. equi merozoites and infected horses by assessing cytokine expression during primary and secondary parasite exposure, and to determine whether the pattern of expression correlated with clinical indicators of disease. Our findings showed that the expression of pro-inflammatory cytokines was very low and inconsistent during both primary and secondary infection. There was also no correlation between the symptoms observed during primary infection and expression of the cytokines. This suggests that the symptoms might have occurred primarily due to hemolysis and likely not the undesirable effects of pro-inflammatory responses. However, IL-10 and TGF-β1 were highly expressed in both phases of infection, and their expression was linked to antibody production but not moderation of pro-inflammatory cytokine responses.

Molecular and Serological Detection of Vector-Borne Pathogens Responsible for Equine Piroplasmosis in Europe between 2008 and 2021

Equine piroplasmosis (EP) is caused by Theileria (T.) equi and/or Babesia (B.) caballi. The aim was to assess the percentage of positive test results for EP in horses in Europe and to identify risk factors for pathogen contact/infection. This study included results from PCR and competitive enzyme-linked immunosorbent assay testing requested by European veterinarians between 2008 and 2021. Binary bivariate logistic regression was used to analyze risk factors. A total of 4060 horses were included. PCR testing was positive in 9.7% (154/1589), serology for T. equi in 15.2% (393/2591) and for B. caballi in 6.8% (175/2578). The odds of positive serology increased by 6.8% (B. caballi, p = 0.008) and 9.5% (T. equi, p < 0.001) each year. Regionality had a statistically significant impact on PCR (Eastern p = 0.047/OR = 1.605; Southern p = 0.029/OR = 1.451; Central p = 0.007/OR = 0.617) and serological testing for T. equi (Southern p < 0.001/OR = 2.521; Central p < 0.001/OR = 0.537; Northern p = 0.003/OR = 0.462), as well as breeds on seroprevalence of B. caballi (heavy horses: p = 0.016/OR = 2.239) and T. equi (ponies: p = 0.007/OR = 0.340; warmbloods: p = 0.025/OR = 1.602). In conclusion, there was a significant geographical impact on the results of PCR and serology, consistent with known vector habitats. The rising numbers of horses tested serologically positive highlights the importance of surveillance.

Diagnostic performance of a rapid immunochromatographic test for the simultaneous detection of antibodies to Theileria equi and Babesia caballi in horses and donkeys

BACKGROUND

Equine piroplasmosis is caused by two tick-borne protozoan parasites, Theileria equi and Babesia caballi,, which are clinically relevant in susceptible horses, donkeys, and mules. Moreover, equine piroplasmosis significantly constrains international trading and equestrian events. Rapidly diagnosing both parasites in carrier animals is essential for implementing effective control measures. Here, a rapid immunochromatographic test for the simultaneous detection of antibodies to T. equi and B. caballi was evaluated using samples from horses and donkeys collected in Greece, Israel, and Italy. The results were compared with an improved competitive enzyme-linked immunosorbent assay (cELISA) for detecting antibodies to both parasites using the same panel of samples.

METHODS

Blood samples were collected from 255 horses and donkeys. The panel consisted of 129 horses sampled at four locations in northern Greece, 105 donkeys sampled at four locations in Sicily, and 21 horses sampled at two locations in Israel. The rapid test and the cELISA were performed according to the manufacturer's instructions, and the results were subjected to a statistical analysis to determine the sensitivity and specificity of both tests and their association.

RESULTS

The immunochromatographic test provided a result within 15 min and can be performed in the field, detecting both pathogens simultaneously. The overall coincidence rate between the rapid test and the cELISA for detecting antibodies against T. equi was 93% and 92.9% for B. caballi. The rapid test's sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for T. equi were above 91.5%. Sixteen samples were positive for both parasites in the rapid test and eight in the cELISA. Either test had no significant association between T. equi and B. caballi detection. The detection rates of both parasites were significantly higher in Italy than in Greece or Israel and in donkeys than in horses. The agreement for T. equi between the results of both tests was high in Greece (93.8%) and Italy (95.2%) and moderate in Israel (76.2%). For B. caballi, the specificity and NPV of the rapid test were high (94.2% and 98.3%, respectively), although the sensitivity and PPV were moderate (69.2% and 39.1%, respectively) due to the small sample size. However, for B. caballi, the sensitivity was higher with the rapid test.

CONCLUSIONS

The rapid test detected T. equi and B. caballi simultaneously in the field, potentially replacing laborious cELISA testing and is recommended for import/export purposes. The test can also be helpful for the differential diagnosis of clinical cases, since seropositivity may rule out equine piroplasmosis since it does not indicate current or active infection.

Development and evaluation of specific polymerase chain reaction assays for detecting Theileria equi genotypes

BACKGROUND

Theileria equi causes equine piroplasmosis, an economically significant disease that affects horses and other equids worldwide. Based on 18S ribosomal RNA (18S rRNA sequences), T. equi can be classified into five genotypes: A, B, C, D, and E. These genotypes have implications for disease management and control. However, no conventional polymerase chain reaction (PCR) assays are available to differentiate the genotypes of T. equi. To overcome this limitation, we developed and evaluated PCR assays specific for the detection of each T. equi genotype.

METHODS

A pair of forward and reverse primers, specifically targeting the 18S rRNA sequence of each genotype, was designed. The genotype-specific PCR assays were evaluated for their specificity using plasmids containing inserts of the 18S rRNA sequence of each genotype. Subsequently, the assays were tested on 270 T. equi-positive equine blood DNA samples (92 from donkeys in Sri Lanka and 178 from horses in Paraguay). 18S rRNA sequences derived from the PCR amplicons were analyzed phylogenetically.

RESULTS

Each genotype-specific PCR assay accurately targeted the intended genotype, and did not produce any amplicons when 18S rRNA from other T. equi genotypes or genomic DNA of Babesia caballi or uninfected horse blood was used as the template. Previous studies employing PCR sequencing methods identified T. equi genotypes C and D in the Sri Lankan samples, and genotypes A and C in the Paraguayan samples. In contrast, our PCR assay demonstrated exceptional sensitivity by detecting four genotypes (A, C, D, and E) in the Sri Lankan samples and all five genotypes in the Paraguayan samples. All the Sri Lankan samples and 93.3% of the Paraguayan samples tested positive for at least one genotype, further emphasizing the sensitivity of our assays. The PCR assays also had the ability to detect co-infections, where multiple genotypes in various combinations were detected in 90.2% and 22.5% of the Sri Lankan and Paraguayan samples, respectively. Furthermore, the sequences obtained from PCR amplicons clustered in the respective phylogenetic clades for each genotype, validating the specificity of our genotype-specific PCR assays.

CONCLUSIONS

The genotype-specific PCR assays developed in the present study are reliable tools for the differential detection of T. equi genotypes.

Clinical and epidemiological aspects of the infection by Babesia, Theileria and Trypanosoma species in horses from northeastern Colombia

Piroplasmosis and trypanosomiasis are debilitating diseases of great economic impact on the equine industry of Latin America. Considering the lack of studies in the northeastern part of Colombia, this study aimed to determine the epidemiological, clinical and genetic features associated with infection of the Babesia, Theileria, and Trypanosoma species in horses from this geographical area. Two hundred and eighty horses from the Arauca, Meta, and Santander departments were molecularly analyzed for infection with Babesia caballi, Theileria equi, Trypanosoma evansi, and Trypanosoma vivax. Furthermore, clinical, epidemiological and entomological analyses were performed on the data sets. Molecular analysis showed 25.7% and 3.9% prevalence for T. equi and T. evansi, respectively, without positive animals for B. caballi and T. vivax. There were no differences in the prevalence of T. equi between departments, whereas T. evansi was detected exclusively in Santander. A total of 633 ticks were collected from 72 horses across the three departments, with 84.7% corresponding to Dermacentor nitens, 10.9% to Amblyomma cajennense (sensu lato) (s.l). and 4.4% to Rhipicephalus microplus. For T. equi, genetic analyses showed that Colombian isolates belong to genotype C of species, along with sequences of Brazil and Mexico. Epidemiological analysis revealed a significant association between tick infestation and lack of vector control with molecular infection of T. equi, whereas clinical analysis revealed a significant reduction in packed cell volume, red blood cells, and mean corpuscular volume in positive animals to this pathogen. Furthermore, molecular infection by T. evansi was associated with epidemiological characteristics in the Santander department. In conclusion, our analysis revealed a moderate infection rate by T. equi of genotype C in horses from northeastern Colombia, which affects their clinical conditions. Control of ticks and treatment of symptomatic animals should be considered to reduce the economic impact associated with these infections in the equine industry.

Molecular detection of Theileria cervi in equids from México

Equine piroplasmosis is a parasitic illness caused by various protozoa of the Babesia and Theileria genera, which parasitize within red blood cells. The transmission of these pathogens occurs through certain genus of ticks, including Amblyomma, Haemaphysalis, Hyalomma, and Rhipicephalus. In recent times, an increase in the identification of new Theileria species and genotypes has been observed. This is further complicated by the presence of mixed Theileria infections in both mammals and tick vectors, particularly in regions where wildlife and livestock share habitats and vectors. Therefore, the objective of this study is to document the occurrence of Theileria cervi in a non-typical host. A total of 88 horses (Equus caballus) and 10 donkeys (Equus asinus) were sampled in three municipalities in Veracruz, Mexico. Molecular techniques were employed to identify Babesia/Theileria through the amplification of a segment of the 18S-rDNA and hsp70 genes. The phylogenetic reconstruction grouped the obtained sequences into a monophyletic cluster alongside sequences of T. cervi. This work represents the first documented occurrence of T. cervi in equids. These findings have significant implications from an epidemiological point of view. In addition, further studies are needed to determine the distribution and pathogenicity of this species for domestic animals and to develop effective control strategies.

Tick extracellular vesicles in host skin immunity and pathogen transmission

Ticks can transmit a variety of human pathogens, including intracellular and extracellular bacteria, viruses, and protozoan parasites. Historically, their saliva has been of immense interest due to its anticoagulant, anti-inflammatory, and anesthetic properties. Only recently, it was discovered that tick saliva contains extracellular vesicles (EVs). Briefly, it has been observed that proteins associated with EVs are important for multiple tick-borne intracellular microbial lifestyles. The impact of tick EVs on viral and intracellular bacterial pathogen transmission from the tick to the mammalian host has been shown experimentally. Additionally, tick EVs interact with the mammalian skin immune system at the bite site. The interplay between tick EVs, the transmission of pathogens, and the host skin immune system affords opportunities for future research.

A case of equine piroplasmosis in the Tokyo 2020 Olympic Games

Equine piroplasmosis is an infectious disease caused by Babesia caballi and Theileria equi. A competition horse that had been imported to the Equestrian Park for the Tokyo 2020 Olympic Games and had a fever over 40°C and severe anemia was diagnosed with equine piroplasmosis by blood smear and direct polymerase chain reaction (PCR) tests for Theileria equi. Treatment with protozoan anthelmintics and whole blood transfusion diminished the fever, improved the anemia, and allowed the horse to return home safely. Preparation for routine cases of this infection should include the development of a system that allows accurate and prompt international dissemination of information and implementation of quarantine measures.

Chromosome-level genome assembly of Babesia caballi reveals diversity of multigene families among Babesia species

BACKGROUND

Babesia caballi is an intraerythrocytic parasite from the phylum Apicomplexa, capable of infecting equids and causing equine piroplasmosis. However, since there is limited genome information available on B. caballi, molecular mechanisms involved in host specificity and pathogenicity of this species have not been fully elucidated yet.

RESULTS

Genomic DNA from a B. caballi subclone was purified and sequenced using both Illumina and Nanopore technologies. The resulting assembled sequence consisted of nine contigs with a size of 12.9 Mbp, rendering a total of 5,910 protein-coding genes. The phylogenetic tree of Apicomplexan species was reconstructed using 263 orthologous genes. We identified 481 ves1-like genes and named "ves1c". In contrast, expansion of the major facilitator superfamily (mfs) observed in closely related B. bigemina and B. ovata species was not found in B. caballi. A set of repetitive units containing an open reading frame with a size of 297 bp was also identified.

CONCLUSIONS

We present a chromosome-level genome assembly of B. caballi. Our genomic data may contribute to estimating gene expansion events involving multigene families and exploring the evolution of species from this genus.

An Update of Evidence for Pathogen Transmission by Ticks of the Genus Hyalomma

Current and likely future changes in the geographic distribution of ticks belonging to the genus Hyalomma are of concern, as these ticks are believed to be vectors of many pathogens responsible for human and animal diseases. However, we have observed that for many pathogens there are no vector competence experiments, and that the level of evidence provided by the scientific literature is often not sufficient to validate the transmission of a specific pathogen by a specific Hyalomma species. We therefore carried out a bibliographical study to collate the validation evidence for the transmission of parasitic, viral, or bacterial pathogens by Hyalomma spp. ticks. Our results show that there are very few validated cases of pathogen transmission by Hyalomma tick species.

Differential Expression of Immune Genes in the Rhipicephalus microplus Gut in Response to Theileria equi Infection

Rhipicephalus microplus is the only tick species known to serve as a biological vector of Theileria equi for horses and other equids in Brazil. The protozoan T. equi is one of the causal agents of equine piroplasmosis, a major threat in horse breeding systems. Vector competence is closely linked to the pathogens' ability to evade tick defense mechanisms. However, knowledge of tick immune response against infections by hemoparasites of the Theileria genus is scarce. In the present study, the expression of genes involved in immune signaling pathways of R. microplus adults' guts when challenged with a high or low parasitic load of T. equi was evaluated. This research demonstrates divergences in the immune gene expression pattern linked to T. equi infection in R. microplus since the Toll, IMD, and JNK signaling pathways were transcriptionally repressed in the guts of adult ticks infected with T. equi. Moreover, the results showed that different infectious doses of T. equi induce differential gene expression of key components of immune signaling cascades in R. microplus gut, suggesting a link between the intensity of infection and the activation of tick immunity response. The present study adds knowledge to elucidate the gut immune signaling response of R. microplus to T. equi infection. In addition, the generated data can serve as a basis for further investigations to develop strategies for controlling and preventing equine piroplasmosis.

Novel equi merozoite antigen (ema-1) gene heterogeneity in a geographically isolated Theileria equi population in Croatia

BACKGROUND

The apicomplexan haemoparasite Theileria equi, a causative agent of equine piroplasmosis, is an established pathogen of significant welfare and economic concern within the Croatian equine population. A previous large surveillance study of T. equi has identified two distinct parasite populations, one in the north and one in the south, geographically separated by the Dinaric Alps, which traverse the country. This study aimed to further investigate the genetic diversity within these two populations, focussing on allelic variability of the equi merozoite antigen gene, ema-1.

METHODS

Following nested PCR of DNA isolates, the generated ema-1 amplicons were subsequently sequenced and compared by phylogenetic analysis to available sequences representing previously described ema-1 genotypes (groups A-C).

RESULTS

Isolates from the southern T. equi population clustered with the existing ema-1 groups A and B. Strikingly, isolates from the northern population clustered into two novel ema-1 genotypes, named groups D and E.

CONCLUSIONS

This detection of hitherto unreported genotypes suggests that historic geographical isolation has led to a degree of divergent evolution in this northern T. equi population. Additionally, current global regulatory testing of equine piroplasmosis relies heavily on EMA-1 based immunodiagnostics, and the discovery of unique ema-1 genotypes may question the efficacy of current diagnostics in international equine movement, with ramifications for the global equine community.

Low seroprevalence of equine piroplasmosis in horses exported from the Netherlands between 2015 and 2021

Equine piroplasmosis (EP) is a tick-borne disease affecting horses, donkeys, mules and zebras, caused by the intracellular apicomplexan protozoa Babesia caballi and Theileria equi. The geographical distribution of EP is closely related to the distribution of its vector tick species belonging to the genera of Dermacentor, Rhipicephalus and Hyalomma. Since the discovery of Dermacentor reticulatus ticks in 2007 and the first reported autochthonous cases in the South of the Netherlands in 2012, no data on the (sero)prevalence of EP in horses in the Netherlands have been reported and it remains unclear whether B. caballi and T. equi have been able to establish themselves in the Netherlands. This study aims to give an update on the current status of EP in horses in the Netherlands using data from serological tests performed in the context of export and screening of 12,881 horses from 2015 through 2020. Horses were categorized as “Dutch,” “Foreign,” or “Unknown” based on microchip number. The overall seroprevalence of EP in Dutch horses was found to be 0.5% (95% exact CI [0.4–0.7]), compared to 1.9% (95% exact CI [1.3–2.6]) in horses in the category “Foreign” and 1.7% (95% exact CI [1.2–2.3]) in horses in the category “Unknown.” In addition, the seroprevalence per country in the category “Foreign” ranged from 0% (0.95% exact CI [0–2.8]) for Ireland to 6.0% (0.95% exact CI [3.5–9.3]) for Spain. In light of the reports on the seroprevalence during the outbreak of autochthonous EP reported in 2012 and on seroprevalences of EP in other countries in Northwestern Europe, the seroprevalence of EP in horses exported from the Netherlands is very low. However, the higher seroprevalence of EP in horses from abroad warrants the need for the monitoring of EP, as tick vectors are present in the Netherlands and the import of horses from endemic areas increases the chances of EP becoming more prevalent in the Netherlands.

Changes in Perioperative Antimicrobial and Anti-Inflammatory Drugs Regimens for Colic Surgery in Horses: A Single Center Report

Simple Summary

The administration of postoperative anti-inflammatory and antimicrobial drugs after colic surgery is based on an empirical approach, and for this reason, in recent years, it has been questioned. Recent guidelines recommend that antimicrobials should be administered for the shortest effective period possible. The use of non-steroidal anti-inflammatory drugs is also discussed given the side effects especially on the gastrointestinal tract. Consequently, the antimicrobial and anti-inflammatory drugs administration in horses has changed in our practice over the years to modulate therapies according to the postoperative complications that eventually arise. The description of these changes and the reasons behind them can help define an appropriate stewardship. Over the years, the administration of postoperative antibiotics has been limited, and treatments have been started only in case of complications that justified their use. As for anti-inflammatories, there was a variation of dosages of flunixin meglumine and the addition of new types of anti-inflammatories, both non-steroidal anti-inflammatory drugs and corticosteroids. These changes in prophylaxis protocols were not associated with an increase in postoperative complications.

Abstract

Reducing postoperative incisional infection is the main reason to administer postoperative antimicrobials (AMD) after emergency laparotomy in horses, while reducing inflammation and providing analgesia are the reasons to administer anti-inflammatory drugs (AID). The basis for postoperative AMD and AID administration is empirical and only recently has been questioned. Empirical approaches can be changed, and these changes, along with the description of their outcomes, can help produce appropriate stewardship. The aim of this study is to report the changes in AMD and AID regimens in horses undergoing emergency laparotomy at a referral teaching hospital between 2017 and 2021. Signalment, pathology, surgery, prophylactic AMD and AID administration were obtained from the medical records. Difference in AMD and AID regimens throughout the study period were also reported. In 234 postoperative records considered, ninety-two horses received prophylactic AMD, while 142 received pre-operative antimicrobials only. There was a progressive change in regimens throughout the years, increasing the number of AID molecules used. AMD and AID administration in horses has changed in our practice over the years to modulate therapies according to the postoperative complications that eventually arise. In this study, horses not receiving postoperative routine AMD treatment did not show an increased incidence of complications.

Seroprevalence of Anti-Theileria equi Antibodies in Horses from Three Geographically Distinct Areas of Romania

Equine piroplasmosis (EP) is an endemic tick-borne disease found in most countries around the world. It affects all species of Equidae, and it is caused by Theileria equi, Babesia caballi and T. haneyi. The research herein is the second study on the prevalence of piroplasms in Romania conducted in the past two decades. The aim of this study was to assess the seroprevalence of anti-Theileria equi antibodies and the geographical distribution of this disease in the southwest, west, and northwest regions of Romania in order to obtain a more thorough understanding of the parasitological status of horses in this country. This study included 522 apparently healthy, mixed-breed horses from three different counties. The serum samples were analysed using the cELISA Theileria equi Antibody Test Kit. The overall seroprevalence rate was 12.84%. From the total number of positive horses, 13.96% were females and 11.21% were males. Based on the distribution of positive cases into age groups, the following values were obtained: 0−60 months: 16.26%, 60−180 months: 10.03%, and >180 months: 15.83%. There was no statistically significant difference between samples, based on age or gender. The positivity percentage in the localities included in the study ranged from 8.33 to 100%. In the population under study, the seroprevalence rate was high, indicating a possible exposure risk in this area of Romania, which could have severe effects on equids in the case of clinical manifestations of the disease. EP represents a serious threat for equine health in Romania; therefore, close and continuous monitoring of the situation is required.

Development of Nested PCR and Duplex Real-Time Fluorescence Quantitative PCR Assay for the Simultaneous Detection of Theileria equi and Babesia caballi

Equine piroplasmosis (EP) is a type of blood protozoan disease caused by tick-borne parasites, Theileria equi (T. equi), Babesia caballi (B. caballi) and Theileria haneyi. While many studies have been conducted on EP diagnosis, diagnostic methods exhibiting high sensitivity and specificity remain lacking. Therefore, nested PCR (nPCR) and duplex real-time fluorescence quantitative PCR (qPCR) that can simultaneously detect both T. equi and B. caballi causing agents were established and compared. The two techniques were used to analyze 36 horse blood samples for EP. This set of samples was also detected by a multinested PCR (mnPCR) targeting the EMA-1 gene of T. equi and the RAP-1 gene of B. caballi. By nPCR, duplex real-time fluorescence qPCR and mnPCR, infections with B. caballi were detected in 16.67% (6/36), 2.78% (1/36), 19.44% (7/36) of the horses, respectively. The T. equi prevalence was 58.33% (21/36) by the nPCR, 33.33% (12/36) by the duplex real-time fluorescence qPCR and 2.78% (1/36) by the mnPCR. The overall prevalence of infection with mixed parasites by nPCR was 5.56% (2/36), by duplex real-time fluorescence qPCR was 2.78% (1/36) and by mnPCR 0% (0/36). Results suggest that nPCR can detect T. equi and B. caballi positive samples with good specificity and sensitivity, although distinguishing between the two parasites requires an electrophoresis with 4% agarose gels. The duplex real-time fluorescence qPCR can readily distinguish between T. equi and B. caballi infection, but with low sensitivity.

First detection of Theileria equi in free-roaming donkeys (Equus africanus asinus) in Sri Lanka

Equine piroplasmosis (EP) is a tick-borne disease caused by Theileria equi and Babesia caballi in equids, including horses, donkeys, zebras, and mules. It is globally endemic with significant economic impact on the equine industry. Infected animals may serve as carriers, and they may be a source of infection for ticks, thereby posing a great challenge for disease management. Sri Lanka is a tropical country, where infections by various tick-borne parasites are common among livestock animals. However, infections by T. equi and B. caballi remain unstudied in Sri Lanka. Therefore, in the present study, we conducted an epidemiological survey to investigate the presence of T. equi and B. caballi in apparently healthy free-roaming donkeys. Blood samples were randomly taken from 111 donkeys in Mannar (n = 100) and Kilinochchi (n = 11) districts in Sri Lanka. Thin blood smears were prepared from the blood samples and subjected to microscopic examination. Additionally, blood DNA samples were prepared and screened for T. equi and B. caballi infections using species-specific PCR assays. Our results showed that 64 (57.7%) and 95 (85.6%) of the donkeys were positive for T. equi by microscopy and PCR, respectively. However, all samples were negative for B. caballi. Phylogenetic analysis of the T. equi 18S rRNA sequences detected two distinct genotypes, namely C and D. To our knowledge, this is the first report of T. equi in Sri Lanka and of genotype C in donkeys. The present study highlights the importance of monitoring the shrinking donkey population in Sri Lanka owing to EP caused by T. equi.

Development of a Test Card Based on Colloidal Gold Immunochromatographic Strips for Rapid Detection of Antibodies against Theileria equi and Babesia caballi

Equine piroplasmosis (EP) is a serious problem in the horse industry, and controlling EP is critical for international horse trading. EP is caused by two apicomplexan protozoan parasites, Theileria equi and Babesia caballi. Rapid and accurate methods that are suitable for detecting these parasites in the field are crucial to control the infection and spread of EP. In this study, we developed a card to detect antibodies against T. equi and B. caballi based on two colloidal gold immunochromatographic strips according to the principle of the double-antigen sandwich. The proteins equi merozoite antigen 1 (EMA1) and rhoptry protein BC48 are commonly used as diagnostic antigens against T. equi and B. caballi, respectively. On the strip, the purified EMA1 or BC48 protein labeled with colloidal gold was used as the detector, and nitrocellulose membranes were coated with EMA1 or BC48 and the corresponding MAb as the test and control lines, respectively. The protocol takes 10 to 15 min and requires no specialized equipment or chemical reagents, and one test can detect two EP pathogens in one card. Specificity tests confirmed there was no cross-reactivity with sera positive for common equine pathogens. Using a commercial competitive enzyme-linked immunosorbent assay (cELISA) kit for comparison, 476 clinical samples were tested with the card. The coincidence rates were 96.43% and 97.90% for T. equi and B. caballi, respectively. The field trial feedback was uniformly positive, suggesting that this diagnostic tool may be useful for controlling the spread of T. equi and B. caballi.

IMPORTANCE Equine piroplasmosis (EP), caused by Theileria equi and Babesia caballi, is an important tick-borne disease of equines that is prevalent in most parts of the world. EP is considered a reportable disease by the World Organization for Animal Health (OIE). The accurate diagnosis and differentiation of T. equi and B. caballi are very important for the prevention, control, and treatment of EP. Therefore, we developed a double-antigen sandwich colloidal gold immunochromatography assay (GICG) to detect T. equi and B. caballi. Two GICG strips were assembled side by side on one card for the detection of T. equi and B. caballi, and the two EP pathogens could be detected in one test. This method was simple, rapid, and specific for the detection of EP; therefore, compared to the previous methods, this method is more suitable for pathogen diagnosis in the field.

Spatial and Temporal Circulation of Babesia caballi and Theileria equi in France Based on Seven Years of Serological Data

Caused by two blood parasites, Babesia caballi and Theileria equi, equine piroplasmosis is a tick-borne disease that poses major health and economic issues for the equine industry. Our objective was to gain insight into the spatio-temporal variations of parasite circulation in France, where the disease is known to be enzootic, but has been the subject of few studies. Seroprevalence was assessed for each parasite thanks to 16,127 equine sera obtained between 1997 and 2003 from all over France and analysed through complement fixation tests. Results indicated that 13.2% (5-27% depending on the region) of horses were seropositive for T. equi and 9.5% (3-25%) for B. caballi. Regardless of the year, horses from the southern regions of France were the most affected by B. caballi or T. equi infection, while the proportion of horses having antibodies against T. equi increased over time. These results highlight the heterogeneity of the circulation of both piroplasms, which may be linked with ecological diversity and vector distribution. Our data provide baseline information regarding the sero-epidemiology of B. caballi and T. equi infection in horses in France, making it now possible to select regions for future studies on risk factors, and design and implement effective targeted measures against equine piroplasms.

Development of a duplex real-time PCR assay for simultaneous detection and differentiation of Theileria equi and Babesia caballi

Equine piroplasmosis (EP) is a tick-borne disease caused by three apicomplexan protozoan parasites, Theileria equi (T. equi), Babesia caballi (B. caballi) and T. haneyi, which can cause similar clinical symptoms. There are five known 18S rRNA genotypes of T. equi group (including T. haneyi) and three of B. caballi. Real-time PCR methods for detecting EP based on 18S rRNA analysis have been developed, but these methods cannot detect all genotypes of EP in China, especially genotype A of T. equi. In this study, a duplex real-time PCR detection method was developed for the simultaneous detection and differentiation of T. equi and B. caballi. The primers and probes for this duplex real-time PCR assay were designed based on the conserved 18S rRNA gene sequences of all genotypes of T. equi and B. caballi including Chinese strain. Double-quenched probes were used in this method, which provide less background and more signal to decrease the number of false positives relative to single-quenched probes. The newly developed real-time PCR assays exhibited good specificity, sensitivity, repeatability and reproducibility. The real-time PCR assays were further validated by comparison with a nested PCR assay and a previous developed real-time PCR for EP and sequencing results in the analysis of 506 clinical samples collected from 2019 to 2020 in eleven provinces and regions of China. Based on clinical performance, the agreements between the duplex real-time PCR assay and the nPCR assay or the previous developed real-time PCR assay were 92.5% (T. equi) and 99.4% (B. caballi) or 87.4% (T. equi) and 97.2% (B. caballi). The detection results showed that the positivity rate of T. equi was 43.87% (222/506) (10 genotype A, 1 genotype B, 4 genotype C, 207 genotype E), while that of B. caballi was 5.10% (26/506) (26 genotype A), and the rate of T. equi and B. caballi coinfection was 2.40% (12/506). The established method could contribute to the accurate diagnosis, pathogenic surveillance and epidemiological investigation of T. equi and B. caballi infections in horses. This article is protected by copyright. All rights reserved.

Babesiosis and Theileriosis in North America

Babesia and Theileria are apicomplexan parasites that cause established and emerging diseases in humans, domestic and wild animals. These protozoans are transmitted by Ixodid ticks causing babesiosis or theileriosis, both characterized by fever, hemolytic anemia, jaundice, and splenomegaly. In North America (NA), the most common species affecting humans is B. microti, which is distributed in the Northeastern and Upper Midwestern United States (US), where the tick vector Ixodes scapularis is established. In livestock, B. bovis and B. bigemina are the most important pathogens causing bovine babesiosis in tropical regions of Mexico. Despite efforts toward eradication of their tick vector, Rhipicephalus microplus, B. bovis and B. bigemina present a constant threat of being reintroduced into the southern US and represent a continuous concern for the US cattle industry. Occasional outbreaks of T. equi, and T. orientalis have occurred in horses and cattle, respectively, in the US, with significant economic implications for livestock including quarantine, production loss, and euthanasia of infected animals. In addition, a new species, T. haneyi, has been recently discovered in horses from the Mexico-US border. Domestic dogs are hosts to at least four species of Babesia in NA that may result in clinical disease that ranges from subclinical to acute, severe anemia. Herein we review the pathogenesis, diagnosis, and epidemiology of the most important diseases caused by Babesia and Theileria to humans, domestic and wild animals in Canada, the US, and Mexico.

Rapid Detection of Equine Piroplasms Using Multiplex PCR and First Genetic Characterization of Theileria haneyi in Egypt

Equine Piroplasmosis (EP) is an infectious disease caused by the hemoprotozoan parasites Theileria equi, Babesia caballi, and the recently identified species T. haneyi. Hereby, we used a multiplex PCR (mPCR) targeting the 18S rRNA gene of T. equi and B. caballi for the simultaneous detection of EP in Egyptian equids and examined the presence of T. haneyi infections in Egypt. Blood samples from 155 equids (79 horses and 76 donkeys) collected from different governorates of Egypt were examined by mPCR and PCR targeting T. hayeni. The mPCR method revealed a prevalence of T. equi of 20.3% in horses and of 13.1% in donkeys and a prevalence of B. caballi of 1.2% in horses. B. caballi was not detected in donkeys in the current study. The mPCR method also detected coinfections with both species (2.5% and 1.3% in horses and donkeys, respectively). Additionally, we report the presence of T. haneyi in Egypt for the first time in 53.1% of the horse and 38.1% of the donkey tested samples. Coinfection with T. haneyi and T. equi was found in 13.5% of the samples, while infection with the three EP species was found in 1.9% of the samples.

Experimental Infection of Ticks: An Essential Tool for the Analysis of Babesia Species Biology and Transmission

Babesiosis is one of the most important tick-borne diseases in veterinary health, impacting mainly cattle, equidae, and canidae, and limiting the development of livestock industries worldwide. In humans, babesiosis is considered to be an emerging disease mostly due to Babesia divergens in Europe and Babesia microti in America. Despite this importance, our knowledge of Babesia sp. transmission by ticks is incomplete. The complexity of vectorial systems involving the vector, vertebrate host, and pathogen, as well as the complex feeding biology of ticks, may be part of the reason for the existing gaps in our knowledge. Indeed, this complexity renders the implementation of experimental systems that are as close as possible to natural conditions and allowing the study of tick-host-parasite interactions, quite difficult. However, it is unlikely that the development of more effective and sustainable control measures against babesiosis will emerge unless significant progress can be made in understanding this tripartite relationship. The various methods used to date to achieve tick transmission of Babesia spp. of medical and veterinary importance under experimental conditions are reviewed and discussed here.

Molecular Identification of Selected Tick-Borne Protozoan and Bacterial Pathogens in Thoroughbred Racehorses in Cavite, Philippines

Tick-borne diseases (TBDs) considerably impair equine health and productivity. Moreover, TBDs, particularly equine piroplasmosis, impede international movement and trade of equids, which is a vital component of the global horse racing industry. In the Philippines, horse racing is a lucrative industry generating millions of USD annually. However, information on equine TBDs is scarce. This study intended to describe molecularly the equine tick-borne infections in a racehorse park in Cavite, Philippines and identify the risk factors associated with the infections. One hundred twenty-four (n = 124) thoroughbred racehorses were sampled and screened for selected tick-borne protozoan and bacterial pathogens using polymerase chain reaction (PCR) assays. Racehorses were positive for Babesia caballi (12.10%; 15/124), Theileria equi (0.81%; 1/124), Anaplasma phagocytophilum (10.48%; 13/124), Borrelia burgdorferi sensu lato (38.71%; 48/124), A. marginale (0.81%; 1/124), and Coxiella burnetii (0.81%; 1/124). Rickettsia was not detected in the samples. Gender was determined as a significant risk factor for B. caballi infection. Sequencing analysis revealed that seven partial 18S rRNA B. caballi isolates shared 98.63–100% identity with each other and were classified as genotype A. Meanwhile, the sequence obtained from the lone T. equi-positive sample was 99.77% identical to isolates from Spain, Switzerland, China, Saudi Arabia, and South Korea, and was confirmed as genotype E based on the 18S rRNA gene. Eight Anaplasma 16S rRNA partial sequences were highly identical to A. phagocytophilum and A. ovis. Partial sequences of Borrelia 5–23S rRNA were most closely related to B. japonica and other Borrelia sp. isolates from various countries. This study reports the first molecular detection of Borrelia and Anaplasma and the identification of B. caballi and T. equi genotypes in racehorses in the Philippines. Findings from this study shall be useful in crafting equine tick and TBD control and prevention programs in the country.

Molecular detection and phylogenetic characterization of Theileria equi in horses (Equus caballus) from a peri-urban area of Argentina

To investigate the presence of Theileria equi in an endemic area of equine piroplasmosis 42 horses (Equus caballus) from Corrientes City, Argentina were sampled. Eighty-one percent (34 blood samples) of the analyzed horses were tested positive to the presence of piroplasmid 18S rDNA. All these samples could be identified as T. equi by amplifying the specific EMA-1 (merozoite antigen 1) gene of this species. Phylogenetic analysis of an obtained 18S rDNA complete sequence from one strain resulted in the identification of this sample as T. equi sensu stricto (genotype A). This study presents the first molecular detection and characterization of T. equi by the complete 18S rDNA sequence in Argentina. Based on these results further studies should be carried out to investigate the distribution and heterogeneity of presented genotypes of T. equi in Argentina, which is essential for the diagnosis, prevention and treatment of equine piroplasmosis.

Eco-epidemiology of equine piroplasmosis and its associated tick vectors in Europe: A systematic literature review and a meta-analysis of prevalence

When studying a vector-borne disease, an eco-epidemiological approach is vital for a comprehensive understanding of how the pathogen circulates amongst populations. Equine piroplasmosis (EP), a tick-borne disease caused by the protozoans Babesia caballi and Theileria equi, is endemic in the Mediterranean basin of Europe and causes both animal health and economic issues for the equine sector. With no vaccine available, defining the episystem of the disease can help to identify which components of the host-pathogen-vector-environment system to target to improve preventive measures. In this systematic literature review, we collected relevant data on the eco-epidemiology of EP in Europe. The 62 studies remaining after the selection procedure explored potential vectors, indicators of parasite circulation and putative risk factors of EP. Eight hard tick species were identified as potential vectors of one or both piroplasm species. Meta-analyses were then conducted on prevalence and seroprevalence data in equids in European countries, demonstrating an estimated seroprevalence of 30% and 8% and prevalence of 25% and 2% for T. equi and B. caballi, respectively. Finally, herd management practices and environmental risk factors analysed in studies showed no real consensus between studies, but revealed a general trend highlighting age and exposure to ticks as risk factors, and vaccination as a protective factor. Through this study, we point out that only a few studies have focused on disease management practices and even fewer have studied the effect of environmental parameters on equid infections. Further investigation in these areas is required to better characterize the eco-epidemiology of EP and risk factors associated with this disease.

Detection of Anaplasma Phagocytophilum in Horses With Suspected Tick-Borne Disease in Northeastern United States by Metagenomic Sequencing

Metagenomic sequencing of clinical diagnostic specimens has a potential for unbiased detection of infectious agents, diagnosis of polymicrobial infections and discovery of emerging pathogens. Herein, next generation sequencing (NGS)-based metagenomic approach was used to investigate the cause of illness in a subset of horses recruited for a tick-borne disease surveillance study during 2017–2019. Blood samples collected from 10 horses with suspected tick-borne infection and five apparently healthy horses were subjected to metagenomic analysis. Total genomic DNA extracted from the blood samples were enriched for microbial DNA and subjected to shotgun next generation sequencing using Nextera DNA Flex library preparation kit and V2 chemistry sequencing kit on the Illumina MiSeq sequencing platform. Overall, 0.4–0.6 million reads per sample were analyzed using Kraken metagenomic sequence classification program. The taxonomic classification of the reads indicated that bacterial genomes were overrepresented (0.5 to 1%) among the total microbial reads. Most of the bacterial reads (~91%) belonged to phyla Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, Cyanobacteria and Tenericutes in both groups. Importantly, 10–42.5% of Alphaproteobacterial reads in 5 of 10 animals with suspected tick-borne infection were identified as Anaplasma phagocytophilum. Of the 5 animals positive for A. phagocytophilum sequence reads, four animals tested A. phagocytophilum positive by PCR. Two animals with suspected tick-borne infection and A. phagocytophilum positive by PCR were found negative for any tick-borne microbial reads by metagenomic analysis. The present study demonstrates the usefulness of the NGS-based metagenomic analysis approach for the detection of blood-borne microbes.

Serological and Molecular Prevalence of Babesia caballi in Apparently Healthy Horses in Israel

Babesia caballi is a tick-borne hemoparasite of equines and one of the causative agents of equine piroplasmosis, which poses a great concern for the equine industry regarding animal welfare and international horse movement. The parasite is endemic in Israel; however, its seroprevalence in the area was never evaluated due to antigenic heterogenicity in the gene used in the commercially available kit. Blood samples were collected from 257 horses at 19 farms throughout the country and screened for the presence of anti-B. caballi antibodies via an indirect immunofluorescent antibody test (IFAT) and for the presence of parasite DNA by nested PCR. The seroprevalence of B. caballi was 69.6% and its molecular prevalence was 9.7%. The geographical area, horse’s sex, breed, housing, exposure to ticks, and specifically to Hyalomma marginatum, and co-infection with Theileria equi were found to be significantly associated with serologic exposure in univariable analysis, while the geographical area and horses’ sex remained significant in the multivariable analysis. The results of this study demonstrate a high level of exposure to B. caballi and identify important risk factors for infection. The difference between the serological and molecular prevalence, probably related to parasite clearance, is also highlighted.

First Case of Autochthonous Equine Theileriosis in Austria

A 23-year-old pregnant warmblood mare from Güssing, Eastern Austria, presented with apathy, anemia, fever, tachycardia and tachypnoea, and a severely elevated serum amyloid A concentration. The horse had a poor body condition and showed thoracic and pericardial effusions, and later dependent edema and icteric mucous membranes. Blood smear and molecular analyses revealed an infection with Theileria equi. Upon treatment with imidocarb diproprionate, the mare improved clinically, parasites were undetectable in blood smears, and 19 days after hospitalization the horse was discharged from hospital. However, 89 days after first hospitalization, the mare again presented to the hospital with an abortion, and the spleen of the aborted fetus was also PCR-positive for T. equi. On the pasture, where the horse had grazed, different developmental stages of Dermacentor reticulatus ticks were collected and subjected to PCR, and one engorged specimen was positive for T. equi. All three amplicon sequences were identical (T. equi genotype E). It is suspected that T. equi may repeatedly be transmitted in the area where the infected mare had grazed, and it could be shown that transmission to the fetus had occurred. Due to the chronic nature of equine theileriosis and the possible health implications of infection, it is advised to include this disease in the panel of differential diagnoses in horses with relevant clinical signs, including horses without travel disease, and to be aware of iatrogenic transmission from inapparent carrier animals.

Characterization of the Rhipicephalus (Boophilus) microplus Sialotranscriptome Profile in Response to Theileria equi Infection

This study intends to characterize the sialotranscriptome profile of Rhipicephalus (Boophilus) microplus in response to Theileria equi and identify genes of interest with differential genomic expression, indicating relevant targets in the tick–protozoan interactions. The experimental design consisted of RNA sequencing from uninfected and T. equi-infected R. microplus salivary glands (SGs) to obtain transcriptomic profiles for characterization and comparison. A total of 288,952 transcripts were obtained from both tick profiles, 3456 transcripts (p < 0.05) differentially expressed in response to T. equi infection. The uninfected SGs’ registered 231,179 transcripts, of which 155,359 were annotated. The most transcribed sequences were female-specific histamine binding protein and lipocalins. Regarding the T. equi-infected SGs, from the 238,964 assembled transcripts, 163,564 were annotated. The most transcribed sequences were histone demethylase JARID1 and Y-box-binding protein. Five transcripts (cystatin, arginase, nuclear factor κB kinase inhibitor subunit β (IκB), IκB delta, lysosomal-trafficking regulator, and reeler protein) presented the gene ontology (GO) category “response to protozoan” and were exclusively displayed in the T. equi-infected profile. The transcriptome of T. equi was also analyzed, registering 4728 hits. The study’s genetic and molecular information would be of great value for future studies and biotechnological applications envisaging disease control.

Challenges in Tick-Borne Pathogen Detection: The Case for Babesia spp. Identification in the Tick Vector

The causative agents of Babesiosis are intraerythrocytic protozoa of the genus Babesia. Babesia parasites are present around the world, affecting several mammals including humans, pets and livestock, hence its medical and veterinary relevance. Babesia spp. detection in its invertebrate host is a main point in understanding the biology of the parasite to acquire more knowledge on the host–Babesia–vector interactions, as increasing knowledge of the Babesia lifecycle and babesiosis epidemiology can help prevent babesiosis outbreaks in susceptible mammals. The aim of the present review is to highlight the newest findings in this field, based on a bibliographic compilation of research studies recently carried out for the detection of the main Babesia species found in tick vectors affecting mammalian hosts, including the different tick stages such as adult ticks, larvae, nymphs and eggs, as well as the detection method implemented: microscopic tools for parasite identification and molecular tools for parasite DNA detection by conventional PCR, nested-PCR, PCR-RFLP, PCR-RLB hybridization, real time-PCR, LAMP and RAP assays. Although molecular identification of Babesia parasites has been achieved in several tick species and tissue samples, it is still necessary to carry out transmission experiments through biological models to confirm the vectorial capacity of various tick species.