Development of an indirect ELISA for the diagnosis of equine piroplasmosis

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.

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

Equine piroplasmosis (EP), caused by the hemoparasites Theileria equi, Theileria haneyi, and Babesia caballi, is an important tick-borne disease of equines that is prevalent in most parts of the world. Infection may affect animal welfare and has economic impacts related to limitations in horse transport between endemic and non-endemic regions, reduced performance of sport horses and treatment costs. Here, we analyzed the epidemiological, serological, and molecular diagnostic data published in the last 20 years, and all DNA sequences submitted to GenBank database, to describe the current global prevalence of these parasites. We demonstrate that EP is endemic in most parts of the world, and that it is spreading into more temperate climates. We emphasize the importance of using DNA sequencing and genotyping to monitor the spread of parasites, and point to the necessity of further studies to improve genotypic characterization of newly recognized parasite species and strains, and their linkage to virulence.

Infection dynamics of Theileria equi in carrier horses is associated with management and tick exposure

The tick-borne equine hemoparasite, Theileria equi, is endemic in many parts of the world where prevalence may be high, and most infected horses are apparently healthy but serve as life-long carriers. To determine the factors that affect T. equi dynamics, we followed parasitic loads in apparently healthy horses at four time points during one year. A total of 1094 blood samples were collected from 395 horses, along with ticks and demographic and clinical data. Infection and load of T. equi were tested by PCR and qPCR, and for the spring dataset, infection was also tested serologically by IFAT (n = 268). Theileria equi was molecularly detected in 64.8 % of the horses. The agreement between molecular and serological results was 79.8 % (K > 0.674) and positively correlated with parasitic load. Infection was associated with pale mucus membranes, lower packed cell volume and higher total solids (all P < 0.001), although these changes had only minor clinical importance. While parasitic loads in qPCR-positive samples (n = 561) were generally low (mean = 7.9-10^-4% parasitized erythrocytes), younger horses showed higher loads, possibly suggesting development of immunity. Infection and parasitic load were associated with housing management and tick exposure, illustrating different patterns of exposure. Endemic stability is suggested in pasture farms with constant exposure to ticks, where parasite prevalence was high (96 %) and associated with T. equi 18S rRNA genotype D, low parasitemia and high antibody titers. Endemic instability can be suggested in case were horses are kept in paddocks (prevalence = 49 %) with intermittent exposure to ticks, where infection was associated with high parasitemia when ticks were present. A steady state is suggested in stabled horses (prevalence = 46 %), with no exposure to ticks; where infection was associated with genotype A, low parasitemia and low antibody titers. The ability to identify different risk groups within endemic areas may improve the administration of suitable treatment and control practices in an effort to reduce the risk of clinical disease.

Prevalence of Piroplasma in Ticks Collected from Dogs and Cattle in Guangxi, South China Determined by Reverse Line Blot Hybridization Assay

Piroplasmosis is a disease of domestic and wild animals caused by tick-borne protozoa of the genera Theileria and Babesia. Piroplasmosis leads to substantial economic losses in the livestock industry. This disease has been frequently reported in subtropical and tropical regions worldwide. However, information regarding the prevalence of piroplasma in ticks collected from dogs and cattle is lacking in most areas. To assess the potential threat of piroplasmosis in South China, 671 ticks were collected in Guangxi Province. Deoxyribonucleic acid (DNA) was extracted from these ticks to evaluate the presence of piroplasma through a reverse line blot (RLB) hybridization assay using the hypervariable V4 region of the piroplasmic 18S ribosomal ribonucleic acid (r)RNA genes as probes to detect Theileria and Babesia species. The RLB results indicated that 144/671 (21.46%) ticks were infected with piroplasma species belonging to the genera Theileria or Babesia. Theileria buffeli, Babesia vogeli, Theileria annulata, and Theileria luwenshuni were present in the ticks at frequencies of 60/671 (8.94%), 21/671 (3.13%), 6/671 (0.89%), and 6/671 (0.89%), respectively. Mixed infections with 2 or more piroplasma species were present in 8/671 (1.19%) tick samples. The hypervariable V4 region of the piroplasmic 18S rRNA genes from 6 tick DNA samples with single infections was cloned, sequenced, and aligned to related sequences from GenBank. The Theileria and Babesia sequences were analyzed separately. 18S rRNA gene fragment sequences of T. annulata and T. buffeli were compared with previously reported homologous sequences. All 3 B. vogeli sequences examined in this study were grouped into the same cluster and belonged to the same genotype. The present study provides important epidemiological information regarding piroplasmosis occurrence in China. The existence of tick-borne piroplasma likely leads to high infection risks among the local animals in the studied areas.

C-Terminal region of 48-kDa rhoptry protein for serological detection of Babesia caballi antibodies in horses

A recombinant C-terminal antigen derived from Babesia caballi 48-kDa rhoptry protein (rBc48/CT) was made for the development of a serologically diagnostic test. Antiserum raised against the rBc48/CT reacted specifically with the corresponding native protein by Western blotting and the indirect fluorescent antibody test (IFAT). Next, an indirect enzyme-linked immunosorbent assay (Bc48/CT-ELISA) and an immunochromatographic test based on the Bc48/CT (Bc48/CT-ICT) were constructed and employed for the detection of an antibody to B. caballi in a variety of equine sera. The results of Bc48/CT-ELISA and Bc48/CT-ICT were highly concordant with those of IFAT and ELISA, with full-length protein of Bc48 used as the reference tests. Our results demonstrate the success of Bc48/CT as antigen for the serological diagnosis of B. caballi infection in horses.