Epidemiology of equine histoplasmosis (epizootic lymphangitis) in carthorses in Ethiopia.
Authors: Ameni Gobena
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Equine Histoplasmosis in Ethiopian Cart Horses Between 2003 and 2004, Gobena conducted a large-scale epidemiological survey of 19,082 working horses across 28 Ethiopian towns to characterise the distribution and environmental drivers of epizootic lymphangitis (equine histoplasmosis), a chronic granulomatous disease affecting the skin and lymphatic system. Clinical and microscopic examination revealed an overall prevalence of 18.8%, though this varied dramatically between locations—from 39% in Mojo to zero cases in five towns including Debre Berhan and Dinsho—with statistically significant clustering into high, medium and low prevalence zones. Temperature and altitude emerged as key environmental correlates, with prevalence increasing significantly at lower elevations (1500–2300 m above sea level) and in hotter conditions, whilst rainfall showed no meaningful association; notably, case numbers also scaled directly with local horse population density. The findings underscore that epizootic lymphangitis represents a substantial welfare and productivity concern in Ethiopia's working horse population, particularly in lowland agricultural centres, and highlight the need for geographically tailored biosecurity and management strategies rather than blanket approaches, whilst also suggesting that cooler, higher-altitude regions may offer relative protection against establishment of the disease.
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Practical Takeaways
- •Equine histoplasmosis is a significant disease in Ethiopia affecting 1 in 5 carthorses; practitioners in endemic regions should maintain high clinical suspicion and implement diagnostic protocols
- •The disease shows strong environmental associations with temperature and altitude; carthorses in hot, humid lowland areas (1500-2300m) carry higher infection risk than those in cold or dry upland regions
- •Control strategies should be prioritized in high-prevalence towns and areas with large horse populations, suggesting that disease management interventions should be geographically targeted and scaled to population density
Key Findings
- •Overall prevalence of equine histoplasmosis was 18.8% (3579/19082) across 28 Ethiopian towns
- •Prevalence was significantly associated with average annual temperature (R=0.64, P<0.01) and altitude (R=0.57, P<0.01), but not with rainfall
- •Highest prevalence recorded at Mojo (39%) with zero prevalence in five towns including Agaro, Bokoji, Debre Berhan, Dinsho, and Sagure
- •Disease prevalence increased significantly with horse population density (R=0.88, P<0.001) and was endemic in hot, humid areas between 1500-2300m altitude