African Horse Sickness
Journal: Equine Health
Summary
# African Horse Sickness: The Donkey Reservoir Risk in the UK African horse sickness virus (AHSV), an Orbivirus transmitted by Culicoides biting midges, causes severe and often fatal disease in horses, yet produces milder clinical signs in donkeys—raising concerns that donkeys could function as potential reservoirs if the virus reached Britain. Researchers surveyed Culicoides populations at a southern England donkey sanctuary during spring and summer 2019, collecting 21,350 midges of 20 species using ultraviolet light-suction traps over 14 nights; subgenus Avaritia comprised 91.7% of the population. Notably, the Avaritia subgenus—known vectors of related Orbiviruses in northern Europe and putative AHSV vectors in southern Europe—were confirmed through molecular analysis to blood-feed regularly on donkeys. Given the current scarcity of epidemiological data on UK donkey populations and their potential role in AHSV transmission, this finding highlights a genuine biosecurity concern: should AHSV breach UK borders, the presence of competent vectors and asymptomatic or mildly affected donkey hosts could substantially complicate outbreak control and allow the virus to establish and persist in the equine population. For veterinary practitioners and those involved in disease surveillance, this underscores the importance of monitoring donkey populations alongside horses in any future AHSV risk assessments and disease contingency planning.
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Practical Takeaways
- •Donkeys in the UK may be silent carriers of AHSV if the virus is introduced, making disease surveillance in both equine and donkey populations critical for biosecurity planning.
- •Vector control and monitoring programs should consider donkey sanctuaries and populations as potential transmission nodes, not just horse facilities.
- •Veterinary professionals should maintain awareness of emerging Culicoides-borne diseases in temperate regions, as geographical barriers are no longer reliable protection.
Key Findings
- •21,350 Culicoides midges of 20 species were collected near a donkey sanctuary in southern England, with 91.7% belonging to subgenus Avaritia, known vectors of Orbiviruses.
- •Culicoides blood-feeding on donkeys was confirmed through PCR analysis, demonstrating regular contact between vectors and hosts.
- •Donkeys show lower incidence and severity of AHS compared to horses, raising concern they could serve as potential disease reservoirs.
- •Large populations of Culicoides capable of transmitting AHSV exist near donkey populations in the UK, posing a risk for disease establishment and complicating control efforts.