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Home / Equine Research Bank / Pathogens / Clinical Progression of Theileria haneyi in Splenectomized H...
Pathogens (Basel, Switzerland)2022; 11(2); 254; doi: 10.3390/pathogens11020254

Clinical Progression of Theileria haneyi in Splenectomized Horses Reveals Decreased Virulence Compared to Theileria equi.

Abstract: The global importance of the hemoparasite to equine health was recently shown by its resistance to imidocarb dipropionate (ID) and its interference with clearance by ID in some co-infected horses. Genetic characterization of revealed marked genomic reduction compared to , and initial experiments demonstrated reduced clinical severity in spleen-intact horses. Furthermore, in early experiments, splenectomized horses survived infection and progressed to an asymptomatic carrier state, in stark contrast to the high fatality rate of in splenectomized horses. Thus, we hypothesized that is less virulent than . To objectively assess virulence, clinical data from nine splenectomized, -infected horses were evaluated and compared to published data on -infected, splenectomized horses. Seven of eight splenectomized, -infected horses survived. Further, in six horses co-infected with and , only horses cleared of by ID survived splenectomy and became asymptomatic carriers. The reduced virulence of in splenectomized horses instructs why was, until recently, undetected. This naturally occurring comparative reduction in virulence in a natural host provides a foundation for defining virulence mechanisms of theileriosis and Apicomplexa in general.
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Publication Date: 2022-02-16 PubMed ID: 35215197PubMed Central: PMC8879895DOI: 10.3390/pathogens11020254Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research paper examines the relative virulence of Theileria haneyi (Th) compared to Theileria equi (Te) in splenectomized horses, with the authors concluding that Th is less virulent. This conclusion is based on studies showing a higher survival rate of horses infected with Th versus those infected with Te after spleen removal.

Introduction and Theoretical Basis

  • The research is grounded on recent findings proving the significance of the hemoparasite Theileria to equine health. One of these findings is the resistance of certain strains to the drug imidocarb dipropionate (ID) and interference with its efficacy in some co-infected horses.
  • The scientists also took note of the marked genomic reduction of Theileria haneyi compared to Theileria equi, indicating different biological characteristics between these two parasites.
  • The initial experiments conducted by the research team showed less harmful effects of Th on horses with an intact spleen compared to those infected with Te.
  • Earlier results also revealed that splenectomized horses – horses having their spleen removed – survived Th infection and did not exhibit any clinical symptoms, unlike their counterparts infected with Te, which faced a high mortality rate.

Research Methodology

  • To test their hypothesis of Th being less severe than Te, the scientists examined clinical data from nine splenectomized horses infected with Th and compared these to existing data on Te-infected, splenectomized horses.
  • In addition, they observed cases of horses co-infected with both Te and Th. The survival rates of these horses after their spleen was removed and they were subsequently treated with ID were analyzed.

Findings and Conclusions

  • Most of the splenectomized horses infected with Th (seven out of eight) survived, supporting the hypothesis of Th’s reduced virulence.
  • In the case of the six co-infected horses, only those who received ID treatment to eliminate Th survived spleen removal and no longer displayed any disease symptoms.
  • This observed decreased virulence of Th in splenectomized horses is the reason why its presence was difficult to detect until recently.
  • These results offer valuable insight into understanding the mechanisms that define the virulence of diseases like theileriosis (caused by Theileria) and other diseases within the Apicomplexa phylum.

Cite This Article

APA
Sears KP, Knowles DP, Fry LM. (2022). Clinical Progression of Theileria haneyi in Splenectomized Horses Reveals Decreased Virulence Compared to Theileria equi. Pathogens, 11(2), 254. https://doi.org/10.3390/pathogens11020254

Publication

Pathogens (Basel, Switzerland)
ISSN: 2076-0817
NlmUniqueID: 101596317
Country: Switzerland
Language: English
Volume: 11
Issue: 2
PII: 254

Researcher Affiliations

Sears, Kelly P
  • Department of Clinical Science, Carlson College of Veterinary Medicine, Oregon State University, Corvallis, OR 97331-4801, USA.
  • Department of Veterinary Microbiology and Pathology, Washington State University, College of Veterinary Medicine, Pullman, WA 99164-6630, USA.
Knowles, Donald P
  • Department of Veterinary Microbiology and Pathology, Washington State University, College of Veterinary Medicine, Pullman, WA 99164-6630, USA.
Fry, Lindsay M
  • Department of Veterinary Microbiology and Pathology, Washington State University, College of Veterinary Medicine, Pullman, WA 99164-6630, USA.
  • USDA-ARS, Animal Disease Research Unit, Pullman, WA 99164-6630, USA.

Grant Funding

  • CRIS# #2090-320000-034-00D / USDA-ARS

Conflict of Interest Statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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Citations

This article has been cited 3 times.
  1. Onzere CK, Hulbert M, Sears KP, Williams LBA, Fry LM. Tulathromycin and Diclazuril Lack Efficacy against Theileria haneyi, but Tulathromycin Is Not Associated with Adverse Clinical Effects in Six Treated Adult Horses.. Pathogens 2023 Mar 14;12(3).
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  2. Ozubek S, Ulucesme MC, Aktas M. Discovery of a Novel Species Infecting Goats: Morphological and Molecular Characterization of Babesia aktasi n. sp.. Pathogens 2023 Jan 10;12(1).
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  3. Elchaninov A, Vishnyakova P, Sukhikh G, Fatkhudinov T. Spleen: Reparative Regeneration and Influence on Liver.. Life (Basel) 2022 Apr 22;12(5).
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