Horse imported into Britain may have been infected by West Nile Virus

Electron microscopy of West Nile virus.
Electron microscopy of West Nile virus. Photo: PhD Dre CC BY-SA 3.0 via Wikimedia Commons

A horse imported into Britain from Cyprus in 2013 may have been the UK’s first case of West Nile Virus (WNV), according to researchers.
The study team described the suspected case of West Nile Virus encephalomyelitis  – brain inflammation – in a report published online in the journal, Equine Veterinary Education.

Sonia Gonzalez-Medina and her colleagues said the affected 11-year-old gelding had been imported from Cyprus and travelled through several areas in Europe in which WNV was endemic before arriving at a property in Lincolnshire.

It made the 10-day journey by sea and road. Before transport, the horse had been checked by a vet and certified as healthy. The animal’s vaccination records included shots for equine influenza and tetanus.

The horse arrived at the Lincolnshire yard without a detectable problem, but around 48 hours later developed muscle tremors and what the owner described as a stiff gait.

Clinical signs included muscle twitching, weakness in the hindlimbs and transient lip twitching that quickly progressed to depression and recumbency.

Antibodies specific to WNV were detected in blood taken from the horse, which had no history of vaccination against the virus.

The researchers, from the Animal Health Trust and Oakham Equine Hospital, said the horse improved clinically 10 days after onset and fully recovered in 12 weeks.

Follow-ups after 12 and 20 months did not reveal any ongoing consequences from the infection. The horse was performing adequately at novice level.

The first reports of neurological disease in horses affected by WNV were in the early 1960s in Egypt and France.

The mosquito-borne virus is typically endemic in Africa, the Middle East and southern Asia, with the number of cases and deaths rising in the last 15 years. It has recently become established in southeastern Europe.

The researchers said favourable climatic conditions for mosquitoes and the movement of migratory birds had helped disperse the virus.

Potential mosquito and bird reservoirs existed in Britain, but maintaining the virus would be dependent upon suitable densities of the species, they said.

Gonzalez-Medina, S., Alzola, R. and Newton, J. R. (2016), Suspect West Nile virus encephalomyelitis in an imported horse in the UK. Equine Veterinary Education. doi: 10.1111/eve.12545
The abstract can be read here

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