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Equine veterinary journal2025; 58(2); 320-332; doi: 10.1002/evj.70136

Equine trypanosomiasis, a systematic review: Disease management.

Abstract: Equine trypanosomiasis is a neglected protozoal disease. Objective: To answer the study question: In equines what are the effects of disease management of trypanosomiasis on disease severity (individual level) and disease prevalence (population level) compared to no intervention? Methods: Systematic review. Methods: Studies were identified that described management of naturally occurring equine trypanosomiasis in any country following 'Preferred Reporting Items for Systematic Reviews and Meta-analyses' using eight international databases (1980-2022). Risk of bias was assessed using ROBINS-I. Data synthesis was descriptive. Results: Thirty studies were included (9 case reports, 5 case series, 15 cohorts, 1 randomised non-inferiority trial). Risk of bias was 'serious' (22/30), 'moderate' (7/30), 'low' (1/30). Heterogeneity was high. Disease severity (individual): Trypanosoma evansi: all evaluated trypanocides were effective in blood parasitaemia clearance (weak evidence). Clinical relapses were common (n = 60/241 equines treated; 25%) (strong evidence). Efficacy was poor once neurological signs were present (n = 12/19 equines; 63% mortality) (strong evidence). Trypanosoma equiperdum: a combination protocol could be curative before CNS invasion (weak evidence). Tsetse transmitted trypanosomiasis: Treatment of haemolymphatic disease with isometamidium or diminazene resulted in a positive clinical response (strong evidence). New/recrudescing infections were common in some regions (strong evidence). Trypanosoma vivax: treatment with high-dose diminazene had a poor clinical outcome (weak evidence). Disease prevalence (population): a multifaceted control programme was effective in reducing disease prevalence (weak evidence). Early (<2 days post-infection) treatment was more effective (weak evidence). Reported side effects were uncommon (n = 70/7888 equines; 1%) (strong evidence). Isometamidium chloride (0.5 mg/kg i.v.) can cause a shock response (13%; range 10-14; n = 14/105) (strong evidence). Conclusions: Publication bias, heterogeneity, descriptive data. Conclusions: Short-term trypanocide response for haemolymphatic disease was positive but optimisation of treatment protocols is required to reduce relapse and combat neurotrypanosomiasis. Reliance on trypanocidal treatment alone is common. Side effects are rare but can be severe.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-12-22 PubMed ID: 41429593PubMed Central: PMC12892392DOI: 10.1002/evj.70136Google Scholar: Lookup
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  • Journal Article
  • Systematic Review
  • Review

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.

Overview

  • This systematic review evaluates the effects of disease management strategies for equine trypanosomiasis on both individual disease severity and population-level disease prevalence, comparing interventions to no treatment.

Background

  • Equine trypanosomiasis is a neglected protozoal disease affecting horses and related animals.
  • The disease is caused by different Trypanosoma species including Trypanosoma evansi, T. equiperdum, T. vivax, and tsetse fly-transmitted trypanosomes.
  • Management and treatment of the disease can vary widely and the effectiveness of these interventions needed comprehensive review.

Research Questions and Objectives

  • Primary objective: Assess the effects of disease management on individual animals (disease severity) and population-level disease prevalence.
  • Comparison: Interventions (treatment and control programs) versus no intervention.

Methods

  • Systematic review was conducted according to PRISMA guidelines.
  • Search spanned eight international databases covering literature from 1980 to 2022.
  • Included studies described management of naturally occurring equine trypanosomiasis globally.
  • Thirty studies met inclusion criteria: 9 case reports, 5 case series, 15 cohorts, and 1 randomized non-inferiority trial.
  • Risk of bias was assessed with ROBINS-I tool: majority had serious risk of bias (22/30), 7 moderate, and only 1 low.
  • Due to heterogeneity and study design variations, the data synthesis was descriptive and qualitative rather than quantitative meta-analysis.

Findings – Disease Severity (Individual Level)

  • Trypanosoma evansi:
    • Various trypanocidal drugs were generally effective at clearing parasites from the blood, but evidence was weak.
    • Clinical relapses after treatment were common, occurring in about 25% of treated equines.
    • Once neurological symptoms appeared (indicating CNS involvement), treatment efficacy dropped significantly: 63% mortality rate observed.
  • Trypanosoma equiperdum:
    • Combination treatment protocols could be curative if applied before central nervous system (CNS) invasion, though evidence was weak.
  • Tsetse fly transmitted trypanosomiasis:
    • Treatment of haemolymphatic stage disease with isometamidium or diminazene led to positive clinical responses.
    • New or recrudescent infections were common in some regions, implying challenges in long-term disease control.
  • Trypanosoma vivax:
    • Treatment with high-dose diminazene generally had poor clinical outcomes.

Findings – Disease Prevalence (Population Level)

  • Multifaceted control programs that combined interventions were somewhat effective at reducing overall disease prevalence, although evidence was weak.
  • Early treatment, particularly within two days post-infection, was associated with improved effectiveness in reducing disease impact.

Safety and Side Effects

  • Reported side effects from trypanocidal treatments were rare (~1% of treated equines).
  • Isometamidium chloride (0.5 mg/kg intravenous dose) was noted to cause a shock-like response in approximately 13% of cases, a serious but uncommon adverse effect.

Limitations

  • High heterogeneity among studies limited possibilities for quantitative synthesis.
  • Most studies had serious or moderate risk of bias, limiting strength of conclusions.
  • Descriptive data and the likelihood of publication bias further temper findings.

Conclusions

  • Short-term treatment with trypanocides can effectively manage haemolymphatic trypanosomiasis in equines.
  • However, relapse after treatment is common, and neurotrypanosomiasis is often fatal with current treatments.
  • There is a need to optimize treatment protocols to reduce relapse frequency and improve outcomes for neurological disease.
  • Control programs relying solely on trypanocidal drugs are common but may not be sufficient to sustainably reduce disease prevalence.
  • Although side effects are relatively rare, some can be severe and require vigilance during treatment administration.

Cite This Article

APA
Raftery AG, Gummery L, Garcia K, Mohite D, Capewell P, Sutton D. (2025). Equine trypanosomiasis, a systematic review: Disease management. Equine Vet J, 58(2), 320-332. https://doi.org/10.1002/evj.70136

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 58
Issue: 2
Pages: 320-332

Researcher Affiliations

Raftery, Alexandra G
  • School of Biodiversity, One Health and Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
Gummery, Lauren
  • Three Counties Equine Hospital, Stratford Bridge, Ripple, Tewkesbury, Gloucestershire, UK.
Garcia, Karelhia
  • Faculty of Veterinary Medicine, Veterinary Medical Sciences, University of Calgary, Calgary, Alberta, Canada.
Mohite, Dinesh
  • Federation of Indian Animal Protection Organisations, New Delhi, India.
Capewell, Paul
  • School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
Sutton, David
  • School of Biodiversity, One Health and Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.

MeSH Terms

  • Animals
  • Horse Diseases / parasitology
  • Horse Diseases / drug therapy
  • Horse Diseases / prevention & control
  • Horses
  • Trypanosomiasis / veterinary
  • Trypanosomiasis / drug therapy
  • Trypanosomiasis / parasitology
  • Trypanosoma / classification
  • Trypanocidal Agents / therapeutic use
  • Prevalence

Conflict of Interest Statement

The authors declare no conflicts of interest.

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