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Parasites & vectors2022; 15(1); 401; doi: 10.1186/s13071-022-05484-4

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

Abstract: 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.
© 2022. The Author(s).
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Publication Date: 2022-10-31 PubMed ID: 36316753PubMed Central: PMC9623909DOI: 10.1186/s13071-022-05484-4Google Scholar: Lookup
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Summary

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The research paper investigates the genetic diversity in two populations of Theileria equi, a pathogen that causes equine piroplasmosis, in Croatia. The study reveals the presence of two new genotypes in one population, indicating a potential weakness in existing diagnostic tests and implications for international equine movements.

Introduction and Study Aim

The research focused on Theileria equi, a dangerous pathogen of the equine population, causing equine piroplasmosis, a disease of concern in Croatia due to its significant economic and welfare impacts. This study aimed to explore the genetic diversity in T. equi populations in Croatia, offering an in-depth analysis of variations in the equi merozoite antigen gene, ema-1.

Methods Used

  • DNA was extracted via nested Polymerase Chain Reaction (PCR) from the two different T. equi populations— one in the north of Croatia and the other in the south, divided by the Dinaric Alps.
  • The resulting ema-1 gene segments were sequenced and compared using phylogenetic analysis to existing sequences known to represent previous ema-1 genotypes (groups A-C).

Results of the Study

  • The T. equi strains sourced from the south aligned with the known ema-1 genotypes A and B.
  • Interestingly, those from the northern population fell into two previously undiscovered ema-1 genotypes, named D and E, indicating a divergent evolution in this population.

Conclusions and Implications

  • The discovery of these new genotypes suggests that geographic isolation contributed to a significant difference in evolution in the northern T. equi population.
  • The findings also imply potential problems with current diagnostic tests for equine piroplasmosis, which depend heavily on detecting the EMA-1 antigen. The presence of unique ema-1 genotypes in one population could thus impact the effectiveness of these tests.
  • This discovery could have significant implications for the global equine community, particularly in terms of the international transport of horses, given the potential inability of existing tests to accurately detect the newly discovered genotypes.

Cite This Article

APA
Coultous R, Gotić J, McCann M, Sutton D, Beck R, Shiels B. (2022). Novel equi merozoite antigen (ema-1) gene heterogeneity in a geographically isolated Theileria equi population in Croatia. Parasit Vectors, 15(1), 401. https://doi.org/10.1186/s13071-022-05484-4

Publication

Parasites & vectors
ISSN: 1756-3305
NlmUniqueID: 101462774
Country: England
Language: English
Volume: 15
Issue: 1
Pages: 401

Researcher Affiliations

Coultous, Robert
  • Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK. robert.coultous@glasgow.ac.uk.
Gotić, Jelena
  • Internal Diseases Clinic, Faculty of Veterinary Medicine, University of Zagreb, Zagreb, Croatia.
McCann, Martine
  • School of Veterinary Medicine, University of Glasgow, Glasgow, UK.
Sutton, David
  • School of Veterinary Medicine, University of Glasgow, Glasgow, UK.
Beck, Relja
  • Laboratory for Parasitology, Croatian Veterinary Institute, Zagreb, Croatia.
Shiels, Brian
  • Institute of Biodiversity Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.

MeSH Terms

  • Horses
  • Animals
  • Cattle
  • Theileria
  • Merozoites
  • Theileriasis / parasitology
  • Croatia / epidemiology
  • Babesiosis / parasitology
  • Phylogeny
  • Antigens, Protozoan
  • Horse Diseases / diagnosis

Grant Funding

  • VET/EPDF/2019-1 / Horserace Betting Levy Board
  • Summer Scholarship 2021 / Beaufort Cottage Educational Trust

Conflict of Interest Statement

The authors declare that they have no competing interests.

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Citations

This article has been cited 1 times.
  1. Mendoza FJ, Pérez-Écija A, Kappmeyer LS, Suarez CE, Bastos RG. New insights in the diagnosis and treatment of equine piroplasmosis: pitfalls, idiosyncrasies, and myths. Front Vet Sci 2024;11:1459989.
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