Equine Internal Parasites Life Cycle

Horses are subject to both internal and external parasites. The most common parasites in horses belong to the worm family and include: Tapeworms, strongyles, bots, Ascarids and pinworms. The lifecycle for these parasites, while slightly different, will follow the same general path.

  1. Reproduction

    • The adult parasite resides somewhere in the animal and reproduction occurs. This reproduction can be sexual or asexual depending on the parasite and the circumstances. The female will pass the eggs, which will pass through the digestive system and into the environment.

    Development

    • The eggs will hatch and go through several stages of development before they are ready to infect a new host. These stages of development usually occur either in the soil or in feces. The larvae are carried from place to place on the bottoms of the horse's feet.

    Infection of New Host

    • The infective larvae are ingested when the host animal eats off the ground.

    Maturation

    • The larvae then travel through several systems, completing their maturation, until they reach the organ system of choice. Many parasites reside in the digestive tract, while some live within the lungs or other organs.

    Intermediate Host

    • Some parasites are transmitted by intermediate hosts, or vectors. These hosts will generally pick up the larvae when ingesting the blood or feces of an infected animal. The parasite will complete its intermediate development within the secondary host and will infect a new primary when the secondary host is ingested.