A topical article in the University of Kentucky research publication Equine Disease Quarterly (EDQ) emphasises the brutal truth — if you hear thunder, lightning may strike. Both horses and humans are better off indoors.
Lightning is a giant discharge of electricity that causes a brilliant flash of light, which can travel rapidly over several miles and produces vast amounts of heat and power with millions of electrical volts. If it strikes a person or animal, essentially it causes electrocution.
Clinical signs of lightning strike in horses range from loss of balance to sudden death. The electrical current flows centrally, often via the ear canal, which will have disastrous effects on balance.
An article in the Veterinary Record highlighted two horses that developed central nervous system disease after being struck by lightning, while others are reported to have had their eyesight or hearing destroyed. Nervous tissue does not heal well, so the outcome is unlikely to be good.
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Detective work
A split-second lightning strike can easily be missed. Analysis of weather warnings and other lightning damage in the locality can help confirm whether lightning strike is to blame in a case of sudden death.
Strikes are more likely to be fatal to a horse than a human, simply because horses are bigger and have four feet set on the ground rather than two. As the lightning goes to earth across the body, there is potential for it to affect the electrical rhythm of the heart, causing immediate cardiac arrest.
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The last horse I dealt with that died as a result of lightning strike still had grass in his mouth. The only external evidence was one tiny scorch mark (like a Harry Potter forehead scar) on his coat and a burnt smell. We knew the cause because the owner had seen the storm coming and went to bring her horse in. Sadly, the lightning got there first.
As horses seem unaware of the risks of electrical storms, they will often huddle together in the heavy rain — creating a bigger target. Standing under a single large tree can also be dangerous, especially if it is exposed or on higher ground.
If an electrical storm is forecast, it makes sense to bring horses inside. Riding is similarly risky and not advised.
The recent EDQ report challenged event organisers to develop, implement and communicate a severe weather plan to ensure horse and human safety. It is essential to be weather aware — excellent apps and weather warning systems are now available via the internet and smartphones.
Our equine veterinary expert has more than 30 years experience in practice. She is an FEI vet and has attended the past three Olympic and two World Equestrian Games in her role. She has a particular interest in anaesthesia, pre-purchase examinations, ophthalmology and dermatology amongst other clinical concerns. She has been Horse & Hound’s official veterinary advisor since 1991. Karen is part of the Bell Equine team.
