West Nile Virus in Horses: What You Need to Know

West Nile Virus (WNV) is a mosquito-borne disease that affects both humans and animals, but for horses, it can be particularly dangerous. While rare in the UK, awareness of the disease is growing as climate change and global travel influence the movement of disease-carrying insects. Understanding how to protect your horse is key to prevention and early intervention.

What Is West Nile Virus?

West Nile Virus is a viral infection transmitted primarily by mosquitoes that have fed on infected birds. Horses are considered a “dead-end host,” meaning they can become infected but don’t spread the virus further. However, the consequences of infection can be serious and potentially fatal.

How Is It Transmitted?

Horses become infected through the bite of an infected mosquito. The virus affects the nervous system and can cause a wide range of clinical signs, from mild to severe. WNV is not contagious between horses or from horses to humans.

Symptoms of West Nile Virus in Horses

Symptoms usually appear between 5 to 15 days after infection. While some horses may not show signs at all, others may experience:

• Fever

• Depression or lethargy

• Loss of appetite

• Muscle twitching, especially around the muzzle and flanks

• Incoordination or stumbling

• Weakness or partial paralysis

• Head pressing or circling

• Seizures

• In severe cases, recumbency (inability to stand) and death

Prompt veterinary care significantly increases the chance of recovery.

Diagnosis and Treatment

Diagnosis is confirmed through blood tests that detect the virus or antibodies to it. There is no specific antiviral treatment for WNV, so care is supportive and includes:

• Anti-inflammatories to reduce fever and swelling in the brain

• IV fluids to maintain hydration

• Slings or supportive care for horses that are unable to stand

• Intensive nursing care

Recovery can take weeks to months, and in some cases, neurological symptoms may persist.

Prevention Is the Best Defence

Although rare in the UK currently, prevention is especially important in regions where WNV is endemic or if you plan to travel internationally with your horse.

Prevention Tips:

• Vaccination: In countries where WNV is prevalent, annual vaccination is recommended and effective.

• Mosquito Control:• Remove standing water (buckets, troughs, puddles)• Use mosquito repellents on horses• Install screens in stables or use protective fly sheets

• Travel Smart: Consult your vet before travelling to areas where WNV is known to be present.

Is It a Concern in the UK?

At present, WNV is not widespread in the UK, but with milder winters and warmer, wetter summers, the environment is becoming more favourable for mosquito populations. Vigilance and proactive management are crucial, particularly for horses travelling abroad or located near wetlands.

Final Thoughts

West Nile Virus is a serious neurological disease that can affect horses with little warning. While rare in the UK for now, global changes in climate and ecology mean it could become more relevant in the coming years. Awareness, vaccination (where appropriate), and good stable management are key to reducing the risk.

At Midnight Blue Equestrian, we prioritise horse health and education—because prevention is always better than cure.