Bot larvae in horses

Bots are a type of intestinal parasites that are larvae of the botfly, Gasterophilus. Female botflies lay their eggs by attaching them to the hairs of the horse.

Different species lay their eggs on different parts of the horse’s body.

  • Gasterophilus nasalis lay their eggs between the jaw bones.
  • Gasterophilus hemorrhoidalis lay their eggs on the short hairs of the lip.
  • Gasterophilus intestinalis lay their eggs on the forelimb and shoulder.

Botfly larvae probably cause minimal damage to the stomach but can cause damage to the lining of stomach and cause outflow obstruction.

For more information about Bots, see Stomach Bots in Horses.