Types of Worms that Infect Horses

There are a number of different types of worms that infect horses including bloodworms, tapeworms, large and small red worms, lungworm, pinworms, hairworms, stomach hairworms, neck threadworms, and bots. One of the most common (and most resistant) types of worms in horses is the bloodworm.

Bloodworms are the larvae of the midge family Chironomidae and they can grow up to 6 mm/0.2 inches in length. Because their blood plasma contains haemoglobin, most bloodworms are red in color. While the most recognizable physical characteristic of the bloodworm is its red color, not all bloodworms are red. Some are green and others may have blue bands. Green bloodworms get their color from their environment. Also spelled “hemoglobin,” haemoglobin increases its ability to take up oxygen. The bloodworm (larvae) commonly burrows in the oxygen-poor mud bottom of pools and rivers, so haemoglobin is of great value to the larvae.

UPDATE! All About Worms has partnered with HealthLabs so that
you can get tested for parasites at a fully-qualified lab near you,
no doctor's visit required
! Check it out at HealthLabs.com!

Bloodworms have a distinct head and segmentation is pronounced on the abdomen. Prolegs or “leg like” projections can be found on the first thoracic and last abdominal segments of the bloodworm. The gills are on the last abdominal segment of the bloodworm. Gills can also be found on the segment preceding the last segment. Bloodworms typically frequent surface waters.

Although bloodworms frequent surface waters, they thrive in the horses’ body. Bloodworms may enter the horses body through ingested food or water. They travel by way of the blood vessels to the aorta. The aorta feeds the intestinal tract. The bloodworm matures in the horses’ intestinal tract and then it makes its way into the intestines to lay eggs. Bloodworms can cause inflammation, aneurysms, and colic. Other symptoms of bloodworms in horses include:

  • Tail rubbing
  • Stomach ulcers
  • Diarrhea
  • Dehydration
  • Weight loss
  • Cough/nasal discharge
  • Anemia
  • Poor appetite
  • Rough coat
  • Recurrent colic
  • Pneumonia

Because bloodworms are nearly impossible to eliminate in pastures and surface water, according to American Horse Rider Magazine, the best way to protect your horses from bloodworms is by creating “a good prevention program.” American Horse Rider suggests “putting your animal on a proper treatment schedule that runs every 30 to 45 days once the foal reaches one or two months of age.” In addition, you should visit your vet on a semi-annual basis to conduct a fecal egg count. By doing this, you will have the information needed to adjust your de-worming program if it is not effective. AHR also suggests rotating “different animals into your pasture to break the parasites’ lifecycle.” This way, you will have a good chance of “staying ahead of the game.”

No Paywall Here!
All About Worms is and always has been a free resource. We don't hide our articles behind a paywall, or make you give us your email address, or restrict the number of articles you can read in a month if you don't give us money. That said, it does cost us money to pay our research authors, and to run and maintain the site, so if something you read here was helpful or useful, won't you consider donating something to help keep All About Worms free?
Click for amount options
Other Amount:
What info did we provide for you today?:

Although complete elimination of bloodworms in pastures and surface waters is nearly impossible, it is possible to control bloodworm populations. You can help control populations by not spreading manure in pastures. If you must use manure, break up manure clumps during the dry, summer months. Bloodworms cannot survive dryness and heat. You can also remove manure from the pasture at least once a week.

For more information about bloodworms in horses or other animals, please visit American Horse Rider Magazine at www.horses-and-horse-information or Agri-med.com.

Leave a Comment (but to submit a question please use the "Submit a Question" link above; we can't respond to questions posted as a comment)

Menu / Search

All About Worms