West Nile Fever

West Nile Fever is a neurological disease caused by West Nile Virus (WNV). This virus is carried by mosquitoes Culex spp from infected wild birds only to horses and humans as well.

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Horses and people are end-stage hosts and the virus cannot be transmitted from one to another. The virus can be spread over long distances where there is a wild bird reservoir of infection and mosquitoes. At present there are no WNV reported cases in the UK, but the virus was detected in France, Spain and Italy.

Signs Of West Nile Fever

The virus causes encephalitis (inflammation of the brain) and the clinical signs may include:

  • Elevated body temperature
  • Reduced coordination of the hind limbs
  • Change in behaviour, like not recognising owners
  • Difficulty eating (due to mild paralysis of the facial nerve)
  • Fine tremors of the face and neck muscles
  • Blindness
  • Walking in circles
  • Hyperexcitabilit
  • Seizures
  • Rarely coma and death.

Many infected animals don’t show signs of illness, but they can have detectable blood antibody levels that can be discovered through blood tests and cerebrospinal fluid analysis.

How Long Do Symptoms Of West Nile Fever Last?

Clinical signs in horses that recover can last from 1 day to several weeks and improvement can occur within 5-7 days after the onset of symptoms.

80-90% of horses can return to their normal function 1-6 months after disease and 10% of horses can have deficits like lack of coordination and behavioural changes. Mortality of horses showing clinical signs is between 35-45%.

Protect Your Horses From West Nile Fever

Protection of horses from WNV includes avoiding countries and areas where disease occurs. If you import horses from areas with detected WNV you should discuss quarantine with your vet.

Environmental management is also important like keeping the stables and paddocks free from faeces and organic material, cleaning water buckets and using insect repellent in case of present mosquitoes.

How Is WNV Treated?

The treatment is just supportive and is focused on controlling pain and inflammation. A vaccine is now available in the UK in case of high risk to horses. West Nile Fever is a notifiable disease in the UK, meaning that any suspected cases must be notified to the authorities.

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