Theileria equi in the horses of Iran: Molecular detection, genetic diversity, and hematological findings.
Abstract: In all equids worldwide, Theileria equi and Babesia caballi are believed to be two important erythrocytic protozoa that cause equine piroplasmosis. In addition, it was recently discovered that Theileria haneyi is another potential equine piroplasmosis (EP) agent. Ixodid ticks are the major vectors of these parasites. Equine piroplasmosis is of international importance and affects enormously the equine industry. In this study, for the first time, molecular prevalence and genetic diversity of piroplasma parasites (T. equi and B. caballi) in horses from Fars province (south of Iran) were determined. Also, hematological alterations of naturally infected horses were analyzed. PCR positive horses showed anemia, thrombocytopenia, leukocytosis with a left shift of neutrophilia, and monocytosis. PCR results revealed that, from 133 blood samples of horses, 40 samples were positive (30.07%). The occurrence of T. equi in this area (30.07%) was more than the national average prevalence of T. equi (24.11%), but B. caballi prevalence in study area (0%) was less than the average of previous studies in Iran (5.47%). Our findings revealed that the T. equi was widespread in Fars province of Iran. PCR products of 18S rDNA and EMA-1 genes of T. equi strains were sequenced successfully. All 18S rDNA sequences collected in this experiment revealed 100% similarity together. According to the phylogenetic tree constructed using the 18S rDNA gene, Iranian T. equi is clustered with strains from Cuba (KY111762, KY111761) and USA (CP001669, JX177672). So, this could be concluded that T. equi studied in this research, and those strains are initiated from a common T. equi ancestor at an unknown time ago. Also, the phylogenetic tree based on EMA-1 gene demonstrated a genetically diverse population of Iranian T. equi strains (10 different genotypes). As EMA-1 is one of the most immunogenic antigens in this parasite, such variability could be a concern about the efficacy of T. equi vaccines. Finally, more studies on equine piroplasmosis in the provinces of the southern region of Iran are recommended to create a better vision of disease in this region.
Copyright © 2022 Elsevier B.V. All rights reserved.
Publication Date: 2022-10-05 PubMed ID: 36436901DOI: 10.1016/j.vprsr.2022.100792Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research aimed to analyze and identify the prevalence and genetic diversity of parasites causing the disease, equine piroplasmosis, in horses from the Fars province of Iran. The study found that the infection rate in the region is higher than the national average. All detected strain sequences demonstrated a common ancestry. Differences in gene sequences suggest that vaccine efficacy may be a concern.
Objective of the Study
- The main objective of this research was to understand the prevalence and genetic diversity of piroplasma parasites – specifically, Theileria equi and Babesia caballi – within the horse population in the Fars province of Iran. These parasites cause equine piroplasmosis, a disease that significantly impacts the equine industry worldwide.
Methods and Findings
- The researchers analyzed the blood samples of 133 horses and found that 40 of those samples were infected, resulting in a positive prevalence rate of 30.07% for Theileria equi in the province. This is higher than the national average prevalence rate of 24.11%.
- The prevalence of the other parasite, Babesia caballi, was found to be zero in the study area, which is less than the average prevalence detected in previous studies across Iran (5.47%).
- Horses which tested positive for the parasites exhibited certain hematological alterations such as anemia, thrombocytopenia, leukocytosis with a left shift of neutrophilia, and monocytosis commonly associated with equine piroplasmosis.
Genetic Diversity
- Further, PCR products of 18S rDNA and EMA-1 genes of Theileria equi were sequenced, all resulting 18S rDNA sequences displayed 100% similarity, indicating a common ancestry.
- The phylogenetic tree analysis using the 18S rDNA gene showed that the Iranian T. equi is closely related to strains from Cuba and the USA.
- However, a phylogenetic tree based on the EMA-1 gene demonstrated significant genetic diversity among these parasites and identified 10 different genotypes in the Fars province. EMA-1 is an important immunogenic antigen in these parasites, thus, the observed genetic variability could potentially impact the effectiveness of vaccines currently in use.
Conclusions and Recommendations
- The study recommends further research in the southern region of Iran to provide a clearer picture of the prevalence and diversity of equine piroplasmosis agents and to contribute to the development of more effective solutions and preventative measures.
Cite This Article
APA
Kalantari M, Sharifiyazdi H, Ghaemi M, Ghane M, Nazifi S.
(2022).
Theileria equi in the horses of Iran: Molecular detection, genetic diversity, and hematological findings.
Vet Parasitol Reg Stud Reports, 36, 100792.
https://doi.org/10.1016/j.vprsr.2022.100792 Publication
Researcher Affiliations
- Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
- Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran. Electronic address: sharifiy@shirazu.ac.ir.
- Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
- Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
- Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran.
MeSH Terms
- Cattle
- Horses
- Animals
- Theileria
- Iran / epidemiology
- Babesiosis / parasitology
- Theileriasis / parasitology
- Phylogeny
- Horse Diseases / parasitology
- Babesia / genetics
- Genetic Variation
- DNA, Ribosomal
- Cattle Diseases
Conflict of Interest Statement
Declaration of Competing Interest The authors declare that they have no conflict of interest.
Citations
This article has been cited 2 times.- Dao TTH, Szűts T, Duong NN, Troung DTQ, Solymosi N, Takács N, Hornok S, Farkas R. The first molecular detection of equine piroplasmosis in Vietnam and genetic characterization of three co-circulating genotypes of Theileria equi. Parasitol Res 2026 Feb 5;125(1):14.
- Qin S, Kulabieke T, Mizhamuhan D, Zhang M, Jin M, Abula G, Pi M, Wang H, Zhang Y, Guo Q. Molecular Prevalence and Genotypic Diversity of Theileria equi in Xinjiang, China, Based on Three Genes. Vet Sci 2025 Dec 25;13(1).
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