An outbreak of strangles associated with a novel genotype of Streptococcus equi subspecies equi in donkeys in China during 2018.
Authors: Dong J, Gao N, Waller A S, Cook F R, Fan S, Yuan D, Du Y, Li F, Norimine J, Zhu W
Journal: Equine veterinary journal
Summary
# Strangles outbreak among Chinese donkey herds reveals novel S. equi genotype In July and August 2018, six intensive donkey farms in Shandong Province experienced a significant strangles outbreak caused by *Streptococcus equi* subspecies *equi*, prompting investigation into the prevalence and molecular characteristics of the causative organism. Researchers diagnosed affected animals through bacterial isolation, biochemical testing and PCR, then sequenced the SeM gene of recovered isolates to determine strain identity and compare findings against the PubMLST-seM database. The outbreak affected 13.4% of the total donkey population across the six farms, with markedly higher morbidity in younger animals: 40.3% of foals under one year of age displayed clinical signs, declining to 12.5% in one- to two-year-olds and just 3.8% in animals over two years. Molecular analysis revealed all affected farms harboured the same strain, designated SD201807, which carries a novel SeM 136 allele not previously documented in the literature. Given the expanding intensive donkey farming operations in China and the age-related susceptibility pattern observed, practitioners should recognise strangles as an emerging disease concern in donkey populations, implement rigorous biosecurity protocols on intensively stocked farms, and consider that outbreak management strategies may need adaptation for donkey-specific epidemiology, particularly regarding vaccination of young stock and isolation protocols for susceptible age groups.
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Practical Takeaways
- •Strangles in donkeys shows age-related susceptibility patterns similar to horses; intensively managed young donkeys represent a high-risk population requiring enhanced biosecurity measures
- •A single novel bacterial strain was responsible for multi-farm transmission, emphasizing the importance of quarantine protocols and movement controls between donkey breeding operations
- •As donkey farming intensifies in Asia, practitioners should remain alert for strangles and implement vaccination and management strategies used in equine herds
Key Findings
- •An outbreak of strangles occurred across six donkey farms in Shandong Province, China in July-August 2018 with 13.4% overall prevalence
- •Younger animals were significantly more affected with 40.3% of foals under 1 year showing clinical signs versus 12.5% in 1-2 year-olds and 3.8% in animals over 2 years
- •All affected farms were infected with the same strain (SD201807) carrying a novel SeM allele (136 allele)
- •This is the first documented strangles outbreak in donkey herds in China, highlighting disease transmission risks in intensive breeding operations