Equine seroprevalence of West Nile virus antibodies in the UK in 2019.

There was no evidence for cryptic WNV infection in a cohort of horses sampled in England in 2019. All IgM-seropositive cases were due to vaccination; this should be noted for future epidemiological surveys in the event of a disease outbreak, as it is not possible to distinguish vaccinated from infected horses without knowledge of their clinical histories.