West Nile Virus Confirmed in Dutch Horse - First Autochthonous Case
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South Holland, Netherlands – The first confirmed case of West Nile virus (WNV) in a horse within the Netherlands has been identified in South Holland, marking a significant advancement in the virus’s spread across Europe. The horse exhibited neurological symptoms including muscle tremors, reduced consciousness, and instability, prompting veterinary examination.
This case, definitively confirmed by the European Reference Laboratory for West Nile Virus in horses, represents the first autochthonous infection – meaning the horse contracted the virus within the Netherlands – and raises concerns about potential further spread to both equine and human populations. While WNV has been detected in migratory birds in the country previously, this is the first instance of local transmission to a horse. The finding underscores a growing risk linked to climate change, creating more favorable conditions for the virus-carrying mosquito populations.
Initial testing by a local veterinarian and Royal GD (Animal health Service) revealed the presence of antibodies against WNV. Subsequent analysis at wageningen University & Research detected IgM antibodies, indicating a recent infection. The confirmation via virus neutralization testing solidifies the diagnosis.
Vet Eva dieterman of Royal GD recently stated to De Paardenkrant that a case in dutch horses was “probably only a matter of time,” citing the warming climate as a contributing factor.
West Nile virus is primarily spread through the bite of infected mosquitoes. While horses are considered dead-end hosts - meaning they don’t contribute to further transmission – they are susceptible to severe neurological disease. Humans can also contract WNV through mosquito bites,though most infections are mild.
Further facts on West Nile virus and preventative measures for horses and humans is available through GD Animal Health: https://www.gddiergezondheid.nl/Actueel/Nieuws/2025/10/Eerste-autochtone-infectie-van-paard-met-westnijlvirus-in-Nederland.
Monitoring for West Nile virus has been ongoing in the Netherlands for some time, because the virus is advancing from Southern Europe and Germany.The virus spreads among mosquitoes and birds. Infected mosquitoes can infect both horses and humans. However, a horse cannot infect a human and this virus is not contagious to horses themselves. Only mosquitoes transmit it. Vaccination against this virus is possible for horses, but not for humans. The virus can be particularly hazardous for the elderly. Dozens of people have already succumbed to West Nile disease in Italy by 2025.
Case in South Holland
The horse in South Holland was treated by a local vet after it showed neurological symptoms including muscle tremors, reduced consciousness and instability. These symptoms are typical of West Nile virus. On September 18, blood was taken for examination by Royal GD (Animal Health Service). This showed that the animal had antibodies against the West Nile virus. For confirmation, the same blood sample was forwarded to WBVR, part of Wageningen University & Research. Antibodies were also detected there, including IgM antibodies, which indicates a recent infection. The European Reference Laboratory for West Nile Virus in horses has definitively confirmed the infection via a virus neutralization test.
Advancing virus
Vet Eva Dieterman from Royal GD recently told De Paardenkrant that it was probably only a matter of time before we would see the first cases in horses in the Netherlands. This is partly due to the warming climate. Read more about the West Nile virus and what you can do to protect your horses and yourself in the free long read below.
Bron: GD Animal Health
Article horse newspaper 2025:
Longread on what West Nile Virus is from 2023:
