Insect Bites and Horses

Insect Bites and Horses

Health & Safety

With summer almost here, it's that time of the year when insects can become a real problem for horses. Not only can flies drive them mad, but they can have nasty reactions when biting insects sink their poison into them and the list of pesky creatures is pretty long.

Horses can suffer an extreme toxic reaction when they are bitten by an insect and although quite rare when it happens it can be extremely worrying because the consequences are often serious. When they do have a reaction to any sort of insect bite or sting, horses can appear lethargic and unwilling to move, but other signs of there being something wrong include the following:

  • Standing with their head held low to the ground
  • Breathing heavily and fast – normal this should be 12 breaths a minute
  • An elevated heart rate – normal is 40 beats a minute
  • An unwillingness to move
  • A severe swelling somewhere on their body, face or legs
  • An elevated temperature – normal is anything between 99-101°F

Finding a horse in this condition means calling the vet out as a matter of urgency because it never bodes well when a horse's temperature starts to rise anywhere above the norm. However, it's important to establish whether a horse is having a nasty reaction to an insect sting or whether the swelling is due to something else like an abscess. If the swelling and inflammation is on the lower leg, the vet would need to find out if it is due to trauma or even a fracture. A vet would be able to carry out specific tests to rule these out before establishing what is causing an area to swell and why a horse is suffering from a high temperature and in a lot of pain.

What is Cellulitis?

Cellulitis refers to a condition which is triggered by toxins, a trauma or bacteria and this sets in motion a cellular reaction which in turn sees the body releasing a fluid made up of all sorts of chemicals. These in turn get into the horse's system causing a reaction which is typically swellings and inflammation in a certain area of their body.

The vet would need to examine the affected area very closely where they may find the site of the “sting” or the insect bite that's the cause of the problem. Once this is established, your horse would be made to feel more comfortable with the vet giving them some sort of pain relief together with anti-inflammatory medication administered by injection. The vet may also recommend giving a horse antibiotics and a tetanus jab just to be sure. After which and depending on the severity of a reaction, a horse may need to be put on fluids in order to keep them hydrated.

Biting Insects that Attack Horses

As previously mentioned, there are many biting insects that attack horses here in the UK apart from biting flies that is. These include the following:

  • Horse flies – wherever there is a little water there are bound to be horse flies although wherever there are horses, these biting insects can be found and on hot days they are even worse. They can literally drive a horse mad when they get on their bellies and start biting them
  • Bot flies – also called warble flies can be real pests when they attack and can send horses over the edge which can lead to them injuring themselves in an attempt to get away from these biting insects that leave their eggs on a horse's body
  • Midges – these can swarm and really make life horrible for both horses and their owners
  • Sand flies – another pesky insect that can drive horses mad
  • Wasps – although wasps will not generally attack a horse, if by chance one does sting a horse they can have quite a bad reaction
  • Bees – again bees are not aggressive, but if a horse lies down and this happens to be where a bee is sitting, they will sting and again a horse might have a nasty reaction to the bite
  • Spiders – there are a few spiders that will bite a horse and which could cause a nasty reaction
  • Mosquitoes – with the weather being that much warmer due to global warming there are a lot more insects around than there used to be including biting mosquitoes which can be found in areas of the country where they were never seen before.


There are all sorts of good insect repellent products on the market that are safe to use on horses which can make their lives more comfortable during the hotter summer months. Luckily, horses rarely have a nasty reaction to a bite or sting, but when it happens it can be really frightening because if left untreated the consequences can be quite severe. If you think your horse is having a bad reaction to an insect bite, you should contact your vet straight away so they can examine your horse before recommending the right treatment to get them comfortable again. The one thing you should never do is wait too long before calling the vet out when a horse has a nasty swelling anywhere on their bodies because there are other reasons other than insect bites that could be the cause of a swelling.



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