Analysis of the population structure of Anaplasma phagocytophilum using multilocus sequence typing.
Authors: Huhn Christian, Winter Christina, Wolfsperger Timo, Wüppenhorst Nicole, Strašek Smrdel Katja, Skuballa Jasmin, Pfäffle Miriam, Petney Trevor, Silaghi Cornelia, Dyachenko Viktor, Pantchev Nikola, Straubinger Reinhard K, Schaarschmidt-Kiener Daniel, Ganter Martin, Aardema Matthew L, von Loewenich Friederike D
Journal: PloS one
Summary
# Editorial Summary: Anaplasma phagocytophilum Population Structure and Cross-Species Transmission Risk Anaplasma phagocytophilum, a tick-borne bacterium causing granulocytic anaplasmosis in horses, dogs, cattle and humans, has presented a challenge to standardised surveillance because previous typing methods used different genetic markers and were difficult to compare across laboratories. Huhn and colleagues developed and validated a multilocus sequence typing (MLST) scheme on 383 European and other A. phagocytophilum strains, achieving typability in 74% of isolates and identifying a dominant clonal complex containing 177 strains, alongside a larger number of singleton sequence types suggesting a semiclonal population structure. Significantly, all human, canine and equine strains clustered within the same major clonal complex, implying considerable cross-species transmission potential and suggesting human granulocytic anaplasmosis may be substantially under-recognised in Europe where equine and canine cases are common. The findings also indicate that wild boars and hedgehogs likely serve as reservoir hosts, whereas roe deer, voles and shrews represent minimal zoonotic risk. For equine practitioners, this work provides a standardised diagnostic framework to support epidemiological investigations and indicates that human health authorities should heighten awareness of A. phagocytophilum amongst clinicians in regions where equine and canine disease is established.
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Practical Takeaways
- •Horses with granulocytic anaplasmosis in Europe may pose a zoonotic risk to humans, as equine strains cluster with human-infecting strains and the disease may be underrecognized in people
- •Veterinarians should consider A. phagocytophilum as a potential cause of febrile illness in horses across Europe, particularly when associated with tick exposure
- •The identification of wild boars and hedgehogs as potential reservoir hosts suggests that tick control and wildlife management may be relevant to managing disease transmission in equine populations
Key Findings
- •Multilocus sequence typing achieved 74% typability on 383 A. phagocytophilum strains from humans and animals, establishing a universal typing method for molecular characterization
- •One major clonal complex containing 177 strains was identified, with all human, canine, and equine European strains belonging to the same clonal complex
- •Wild boars and hedgehogs share the same clonal complex as horses and humans, suggesting they may serve as reservoir hosts for A. phagocytophilum in Europe
- •Human granulocytic anaplasmosis is likely underdiagnosed in Europe given the frequent occurrence of equine and canine disease caused by strains in the same clonal complex