Epidemiological Situation of the Exposure to Agents Causing Equine Piroplasmosis in Spanish Purebred Horses in Spain: Seroprevalence and Associated Risk Factors

Development of a Real-Time Quantitative PCR Based on a TaqMan-MGB Probe for the Rapid Detection of Theileria haneyi

Equine piroplasmosis (EP) is a parasitic disease caused by Theileria equi (T. equi), Babesia caballi (B. caballi) and Theileria haneyi (T. haneyi). This disease is considered to be reportable by the World Organization for Animal Health (WOAH). Real-time quantitative PCR (qPCR) is regarded as a straightforward, rapid and sensitive diagnostic method to detect pathogens. However, qPCR has not been employed in the various epidemiological investigations of T. haneyi. In this study, we developed a new qPCR method to detect T. haneyi based on the chr1sco (chromosome 1 single-copy open reading frame (ORF)) gene, which has no detectable orthologs in T. equi or B. caballi. A TaqMan MGB probe was used in the development of the qPCR assay. A plasmid containing the chr1sco gene was constructed and used to establish the standard curves. The novel qPCR technique demonstrated great specificity for detecting additional frequent equine infectious pathogens and sensitivity for detecting diluted standard plasmids. This qPCR was further validated by comparison with an optimized nested PCR (nPCR) assay in the analysis of 96 clinical samples. The agreement between the nPCR assay and the established qPCR assay was 85.42%. The newly established method could contribute to the accurate diagnosis of T. haneyi infections in horses.

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.

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.

Sero-molecular survey and risk factors of equine piroplasmosis in horses in Spain

BACKGROUND

Theileria equi and Babesia caballi cause equine piroplasmosis (EP), one of the most important tick-borne diseases of horses due to its high negative impact to the equine industry. Although infections with these parasites have been reported for decades in Spain, epidemiological studies have only been carried out in certain regions.

OBJECTIVES

To determine the (sero)prevalence of these parasites in asymptomatic horses nationwide in Spain and to identify potential individual and environmental factors associated with seropositivity to EP.

STUDY DESIGN

Sample size was calculated according to the horses registered in Spain in 2013 and by autonomous community using a random stratified sampling. A questionnaire was used to collect data on factors associated with EP seropositivity.

METHODS

Serological (cELISA and complement fixation test) and molecular (real-time PCR) analyses were carried out in 740 horses. Risk factors were identified computing two independent logistic regression models with the collated data.

RESULTS

Antibodies against EP were detected in 42.9% (95% CI 39.4-46.5) of horses, whereas 30.3% (95% CI 27.0-33.6) were EP positive by PCR. A substantial strength of agreement (k = 0.721) was estimated between serological tests. Exposure to T. equi was significantly higher than to B. caballi and the highest (sero)prevalence was detected in the northern communities. Increasing horse age, presence of ticks and contact with cows were factors related to EP seropositivity in the horses, whereas tetanus vaccination and fairs attendance were associated with lower seropositivity.

CONCLUSIONS

Almost half of the horses residing in Spain had antibodies against EP or circulating parasitaemia. Appropriate prevention measures and implementation of a EP surveillance programme should be considered in order to reduce and control the infection.

Seroprevalence and risk factors associated with Equine piroplasmosis in North Egypt

Equine piroplasmosis (EP) is caused by Theileria equi and/or Babesia caballi and has economic importance particularly in equines reared in poor management systems. This study is based on cELISA test to study the seroprevalence of EP among 370 horses and 150 donkeys in four Governorates north Egypt. Additionally, its risk factors were studied for the first time. The seroprevalence rates 36.5 %, 20 %, and 5.6 % for T. equi, B. caballi, and mixed infections, respectively. The highest antibody levels against T. equi were detected in Kafr ElSheikh (40 %) and Giza (40.1 %) Governorates, whereas those of B. caballi were detected in Qalyubia (25 %) and Kafr ElSheikh (24.1 %) Governorates. Concerning T. equi, animals >10 years (OR = 2.06) were more likely to be infected with EP than those <5 years old. In addition, the seropositivity increased among grazing (OR = 5.7, 95 % CI: 1.73-19.27) males (OR = 1.8, 95 % CI: 1.23-2.61) infested with ticks (OR = 2.3, 95 % CI: 1.60-3.48) during summer (OR = 4.3, 95 %CI: 2.53-7.46); whereas the seropositivity of animals for B. caballi increased among grazing equines (OR = 7.8, 95 % CI: 1.05-58.25) over 10 years old (OR = 2.08, 95 % CI: 1.10-3.94) and infested with ticks (OR = 2.4, 95 % CI: 1.54-3.76) during summer (OR = 7.12, 95 % CI: 3.15-16.06). Therefore, EP is an important prevalent disease in Egypt and deserves further attention regarding the management system, treatment, and vector control.

Equine piroplasmosis: an insight into global exposure of equids from 1990 to 2019 by systematic review and meta-analysis

Equine piroplasmosis (EP) is a tick-borne disease of economic importance, relevant in the international movement of equids. The causative agents are at least two apicomplexan protozoan parasites Babesia caballi and Theileria equi. To date, there is no study that estimates global and regional exposure of equids to EP. We therefore conducted a systematic review and meta-analysis to estimate the pooled prevalence and heterogeneity of EP using random-effects model. Six electronic databases were searched for publications on EP and assessed according to Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. A total of 66 eligible studies published between 1990 and 2019 and representing 24 041 equids were included. The overall pooled prevalence estimates (PPEs) of B. caballi was 22.3% (95% CI 21.7-22.8), while the overall PPE for T. equi was 29.4% (95% CI 28.7-30.0). The overall pooled prevalence due to co-infection with both parasites was 11.8% (95% CI 11.32-12.32). Also, subgroup analysis according to sex, age, diagnostic technique, equid species, region and publication years showed a substantial degree of heterogeneity across studies computed for both B. caballi and T. equi infections in equids. Awareness of the current status of EP globally will alert the relevant authorities and stakeholders where necessary on the need for better preventive and control strategies against the disease.

Phylogenetic analysis and geographical distribution of Theileria equi and Babesia caballi sequences from horses residing in Spain

The intraerythrocytic protozoans Theileria equi and Babesia caballi are the causative agents of equine piroplasmosis (EP), one of the most important equine tick-borne diseases due to its significant impact on global international horse trade. Although EP is known to be endemic in Spain, previous phylogenetic studies have only been conducted for limited geographical regions. Therefore, the objective of this study was to evaluate the genetic diversity and distribution of these parasite species nationwide. This was performed by amplification of the 18S small subunit (SSU) rRNA gene from 100 EP positive equine blood samples using a nested PCR protocol, and sequencing the obtained amplicons. Seventy-seven T. equi and six B. caballi isolates were successfully sequenced and phylogenetic analysis revealed that the T. equi isolates grouped into the previously described clades A (n = 21/77), D (n = 1/77) and E (n = 55/77), while B. caballi isolates were placed into clades A (n = 5/6) and B (n = 1/6). Isolates from T. equi clade D and B. caballi clade B have not previously been reported in Spain. A greater intra-clade diversity (97.3-98.3 % identity) was observed between T. equi clade E isolates compared to those within clade A (99.7-100 % identity). Additionally, a multivariable logistic regression model was used to analyse associations between the clade of T. equi infection and available epidemiological data. Horses residing in Spanish northern regions were statistically more likely to be infected with T. equi clade E (p = 0.01). We conclude that while extensive sequence variation of equine piroplasms exists in Spanish infected horses, a requirement for increased equine movement controls between Spain and EP-endemic countries should be considered.

Serological, molecular and hematological diagnosis in horses with clinical suspicion of equine piroplasmosis: Pooling strengths

Equine piroplasmosis (EP) is a tick-borne protozoan disease caused by Theileria equi and/or Babesia caballi. Clinical signs (fever, pale mucosal membranes, jaundice), anemia and hyperbilirubinemia have been associated with the disease. EP is widespread, has a significant economic impact on the equine industry and remains endemic in Spain. This study was carried out with samples belonging to 140 horses residing in Spain and showing common clinical signs of EP. A blood smear microscopic examination and a comparison between the different results obtained by competitive Enzyme-Linked Immunosorbent Assay (cELISA), real-time Polymerase Chain Reaction (PCR) and hematological and biochemical (direct and total bilirubin) screening were conducted. EP positivity rates by cELISA and PCR were 50.7% and 42.9%, respectively, whereas only 9% of the horses were positive in the microscopic analysis. A significantly higher number of B. caballi-positive horses were detected by cELISA than PCR, and Kappa value was higher for T. equi (k = 0.575) than for B. caballi (k = 0.401). For the first time, an association between a high ELISA inhibition percentage (IP) and a positive PCR result for B. caballi was determined. Although most authors have described T. equi as more pathogenic than B. caballi, we found that horses parasitized by B. caballi showed a more severe hemolytic anemia, whereas T. equi infections were mostly associated with leukocytosis. The hemogram and clinical chemistry could guide the veterinary surgeon towards the diagnosis of T. equi or B. caballi since horses showed a significant leukocytosis or anemia and hyperbilirubinemia, respectively; however PCR would be the test of choice in order to confirm the diagnosis. Information about the importance of a correct diagnosis of EP using a combination of techniques is essential in order to allow the early detection of cases and prevent the spread of the disease, as well as to avoid the common practice of treating horses without a laboratory diagnosis.

A multinested PCR for detection of the equine piroplasmids Babesia caballi and Theileria equi

Two haemoparasites, Theileria equi and Babesia caballi, cause equine piroplasmosis (EP), one of the most prevalent tick-borne diseases in horses. The main aim of the present study was to develop and evaluate a multinested PCR (mn-PCR) for simultaneous detection of the equine piroplasmids T. equi and B. caballi, by amplification of five genetic markers (18S rRNA, β-tubulin, cytB, EMA-1 and RAP-1). This novel assay detected a high prevalence of equine piroplasmids in 235 horse blood samples collected in Castilla-León and Extremadura, Spain. The overall prevalence of infection with equine piroplasmids by mn-PCR was 72.8% (171/235), with 66.0% (155/235) of the animals positive for T. equi and 29.4% (69/235) positive for B. caballi. The seroprevalence obtained by cELISA for the same set of samples was lower than the infection prevalence recorded by mn-PCR, for either of the two equine piroplasmids (62.6%) as well as for T. equi alone (61.7%) or B. caballi alone (3.8%). There was high agreement among the mn-PCR and cELISA assays for diagnosis of EP caused by T. equi (κ = 0.83) but not for B. caballi (κ = 0.06). A phylogenetic analysis based on the RAP-1 gene of B. caballi showed that the strains from Spain clustered with those from Israel.