Transient efficacy of buparvaquone against Theileria haneyi in chronically infected horses.
Abstract: Theileria haneyi is one of the three known causative agents of equine piroplasmosis. While imidocarb is generally effective in the clearance of the highly pathogenic Theileria equi, it is ineffective in the treatment of T. haneyi. Moreover, co-infection with T. haneyi has been shown to impede the successful treatment of T. equi. Furthermore, tulathromycin and diclazuril have demonstrated inefficacy in eradicating T. haneyi. The absence of an effective therapeutic agent against this parasite represents a significant obstacle in managing equine piroplasmosis. Methods: To address this issue, we evaluated the efficacy of buparvaquone in the treatment of T. haneyi in chronically infected horses. Results: Our findings showed that treatment of horses with the recommended dose of 2.5 mg/kg of buparvaquone led to a rapid abatement of T. haneyi levels, to a level where the parasites were not detectable by nested PCR. Following treatment, the horses remained PCR negative for a minimum of seven weeks until recrudescence occurred. Subsequent re-administration of buparvaquone at an increased dosage of 6 mg/kg upon recrudescence failed to exert a theilericidal effect on T. haneyi. Throughout the treatment regimen, the hematological parameters of the horses and most components of the chemistry panel remained within the normal range, except for blood urea nitrogen levels, which fell below the normal range in certain instances. Conclusions: BPQ at 2.5 mg/kg and 6 mg/kg had a robust theilericidal effect but was ineffective in the clearance of the T. haneyi infection in persistently infected animals.
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Publication Date: 2024-08-12 PubMed ID: 39129000PubMed Central: PMC11318256DOI: 10.1186/s13071-024-06397-0Google Scholar: Lookup
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Summary
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Transient efficacy of buparvaquone was observed in treating Theileria haneyi infections in chronically infected horses, with temporary clearance followed by parasite recrudescence despite re-treatment.
Background
- Theileria haneyi is one of the three known parasites causing equine piroplasmosis, a disease affecting horses.
- Common treatment with imidocarb effectively clears Theileria equi but fails against T. haneyi.
- T. haneyi co-infections complicate treatment success for T. equi, creating management challenges.
- Other drugs like tulathromycin and diclazuril have also proven ineffective in eliminating T. haneyi.
- The lack of effective treatments for T. haneyi is a major obstacle in controlling equine piroplasmosis.
Research Objective
- To evaluate the efficacy of buparvaquone (BPQ), a known anti-theilerial drug, in treating chronic T. haneyi infections in horses.
Methods
- Horses chronically infected with T. haneyi were administered buparvaquone at 2.5 mg/kg, the recommended dose.
- Parasite levels were monitored using nested PCR, a sensitive molecular detection technique.
- After detecting recrudescence, re-treatment was done with a higher dose of 6 mg/kg BPQ.
- Hematological and biochemical parameters were monitored to assess drug safety and horse health.
Findings
- Initial treatment with 2.5 mg/kg buparvaquone rapidly reduced T. haneyi to undetectable levels by PCR.
- Horses remained PCR-negative for at least seven weeks post-treatment, indicating temporary suppression of infection.
- After seven weeks, the parasite re-emerged (recrudescence), indicating the infection was not cleared.
- Re-treatment with an increased dose of 6 mg/kg BPQ failed to eliminate the parasite, showing resistance or tolerance.
- Blood tests generally remained normal throughout, except for occasional reductions in blood urea nitrogen (BUN) levels, suggesting limited toxicity.
Conclusions
- Buparvaquone at both standard (2.5 mg/kg) and higher (6 mg/kg) doses demonstrates strong initial activity against T. haneyi but does not achieve complete clearance in chronic infections.
- The transient effectiveness, with eventual parasite recrudescence, indicates buparvaquone cannot be relied upon as a curative monotherapy for T. haneyi.
- The ability of the parasite to persist despite treatment underscores the need for alternative therapeutic strategies or combination therapies for managing T. haneyi infections.
- Buparvaquone treatment appeared relatively safe in the tested doses based on hematological and biochemical monitoring.
Implications for Equine Piroplasmosis Management
- Persistent T. haneyi infection remains a challenge due to limited effective drugs.
- Drug resistance or tolerance to buparvaquone may contribute to treatment failure in chronic cases.
- Management strategies should consider monitoring for recrudescence and exploring multi-drug or novel therapies.
- Continued research is needed to find effective, safe agents that can fully clear T. haneyi infections to improve disease control.
Cite This Article
APA
Onzere CK, Hassan A, Sears K, Kappmeyer LS, Villarino NF, Fry LM, Bastos RG.
(2024).
Transient efficacy of buparvaquone against Theileria haneyi in chronically infected horses.
Parasit Vectors, 17(1), 337.
https://doi.org/10.1186/s13071-024-06397-0 Publication
Researcher Affiliations
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA.
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA.
- Department of Animal Medicine, Faculty of Veterinary Medicine, University of Alexandria, Alexandria, Egypt.
- Carlson College of Veterinary Medicine, Oregon State University, Corvallis, OR, USA.
- Animal Disease Research Unit, USDA-ARS, Pullman, WA, USA.
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, USA.
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA.
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA. reginaldo.bastos@usda.gov.
- Animal Disease Research Unit, USDA-ARS, Pullman, WA, USA. reginaldo.bastos@usda.gov.
MeSH Terms
- Animals
- Theileriasis / drug therapy
- Theileriasis / parasitology
- Horses
- Theileria / drug effects
- Horse Diseases / drug therapy
- Horse Diseases / parasitology
- Naphthoquinones / therapeutic use
- Naphthoquinones / pharmacology
- Naphthoquinones / administration & dosage
- Antiprotozoal Agents / therapeutic use
- Antiprotozoal Agents / administration & dosage
- Treatment Outcome
- Chronic Disease
- Male
Grant Funding
- 2090-32000-044-000-D / Agricultural Research Service
Conflict of Interest Statement
The authors declare no competing interests.
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Citations
This article has been cited 3 times.- Kappmeyer LS, Grimsley M, Hicks J, Bastos RG. A high-quality genome sequence of the equine apicomplexan hemoparasite Theileria haneyi Eagle Pass isolate.. Microbiol Resour Announc 2026 Jan 13;15(1):e0056325.
- Poh KC, Oyen K, Onzere CK, Kappmeyer LS, Bastos RG. Haemaphysalis longicornis ticks are unable to transstadially transmit Theileria haneyi to horses.. Front Vet Sci 2025;12:1572944.
- Fernandes TA, Paulino PG, Dos Santos Juliano D, Rabello CA, de Oliveira NVB, de Souza Santana M, Peckle M, Massard CL, da Costa Angelo I, Jacob JCF, Santos HA. Epidemiology and genetic diversity of Theileria equi and Babesia caballi in draft horses in the Distrito Federal, Brazil.. Trop Anim Health Prod 2025 Feb 19;57(2):72.
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