Mosquito Bites

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Diseases and conditions image EquiMed

Also Known As

Bug bites


Typical horse stables and pastures provide a welcome environment for mosquitoes. Since mosquitoes require only standing water or moist soil in which to breed, the proliferation of old tires, tree holes, buckets, water troughs, pools, ditches, and swamps that are often found in areas where horse are kept, serve as a ready breeding ground for these pests.

Mosquito eggs can be laid, larva can develop, and adult mosquitoes emerge in as little as six to seven days during warm, summer months.

When mosquitoes feed on infected birds, rodents, and other animals, they become infected and pass diseases on to horses.

In addition to infections and dermatitis, mosquito bites may infect horses with West Nile Virus and equine encephalomyelitis. When mosquitoes bite a horse, the virus is injected into the bloodstream where it multiplies and crosses the blood/brain barrier.

When the virus infects the brain, it interferes with central nervous system functioning and causes inflammation, leading to severe illness and possibly death. Fortunately, vaccines are available for both West Nile Virus and equine encephalomyelitis.


  • Itching
  • Dermatitis
  • Localized infection


Mosquito bites become a problem when environmental factors create a breeding ground where mosquitoes can thrive and have unfettered access to horses and other animals. Female mosquitoes use blood as a protein source to develop eggs. Mosquitoes tend to bite anywhere on the horse, making it difficult to fend them off.


Prevention of mosquito bites is best accomplished by reducing the population of mosquitoes through reduction of breeding places, using physical barriers such as horse cover sheets to keep mosquitoes off, keeping horses stabled during dawn and dusk hours when mosquitoes are most active, using premise sprays and traps, and applying topical insecticides or repellents.


Mosquito bites are treated with corticosteroid preparations, and, in severe cases, with a short course of steroids. A veterinarian will recommend what will work best for your particular horse.

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