Equine trypanosomiasis, a systematic review and meta-analyses: Prevalence, morbidity and mortality.
Authors: Raftery Alexandra G, Gummery Lauren, Garcia Karelhia, Mohite Dinesh, Capewell Paul, Sutton David G M
Journal: Equine veterinary journal
Summary
# Equine trypanosomiasis: a significant but overlooked global burden Trypanosomiasis remains a neglected protozoal disease affecting equine populations worldwide, yet its true prevalence and clinical impact have never been comprehensively quantified. Raftery and colleagues conducted a systematic review and meta-analyses of 147 prevalence studies and 46 morbidity/mortality studies spanning four decades (1980–2022) across eight international databases, revealing that low and middle-income countries report disease significantly more frequently than high-income countries (33% vs. 9%; odds ratio 5.1), with over 56% of the global equine population residing in medium or high-risk regions. Key findings varied substantially by Trypanosoma species and disease pattern: *T. evansi* outbreaks showed the most severe clinical impact (42% infection rate, 47% morbidity, 23% mortality), whilst tsetse-transmitted trypanosomiasis demonstrated 46% infection rates in outbreak settings but lower mortality at 6%, and endemic disease presented with 50% infection rates and 11% mortality; conservatively, more than eight million equines are estimated to be affected globally with substantial associated morbidity and mortality. For equine practitioners in affected regions—particularly farriers, veterinarians and coaches supporting working horses in endemic areas—these data underscore the need for heightened clinical awareness, improved diagnostic capacity and more robust surveillance systems, as the disease burden is substantially underestimated due to publication bias, heterogeneous reporting standards and missing epidemiological data.
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Practical Takeaways
- •Veterinarians working in or with equines from LMICs should maintain high clinical suspicion for trypanosomiasis; this is a neglected but significant disease causing substantial morbidity and mortality in these regions
- •Trypanosoma evansi presents the most severe clinical picture with nearly 1 in 4 infected horses dying; rapid diagnosis and treatment are critical where this species is endemic
- •Equine practitioners should be aware that over half the world's horse population lives in areas with medium-to-high trypanosomiasis risk, making disease awareness and biosecurity relevant even for non-endemic practitioners managing international horse movements
Key Findings
- •More than 56% of the world's equines (61.5 million) reside in medium/high-risk countries for trypanosomiasis, with >8 million estimated to be affected globally
- •Low and middle-income countries are 5.1 times more likely to report equine trypanosomiasis than higher-income countries (33% vs 9%, p<0.001)
- •Trypanosoma evansi in outbreak settings shows highest mortality at 23% (95% CI 7-54%) with death-to-case ratio of 45%, compared to 6-15% mortality for other species
- •Tsetse-transmitted trypanosomiasis demonstrates infection rates of 46% in outbreaks and 50% in endemic settings with variable but significant morbidity across all Trypanosoma species