Blood Vessels

Parasite: Large Strongyles (Strongylus vulgaris)

Lifecycle:¹

The horse ingests infective larvae, which then penetrate the intestinal wall and migrate along the blood vessels of the abdominal cavity of the horse. The larvae continue to develop until they become mature adults. The adult worms return to the cecum and colon of infected horses, where they lay eggs. The eggs are passed in the feces and the cycle starts over again.

Clinical Signs:

The migration of the immature larval stages of large strongyles through the blood vessels can cause inflammation and blood clots (thrombosis), which can limit blood supply to the intestinal tract. The resulting thromboembolic colic often results in death of the horse. Other clinical signs of large strongyles include anemia, loss of appetite, weakness, emaciation and diarrhea.

Horses at greatest risk:

Large strongyles are now considered rare, especially in well-cared-for horse populations, thanks to effective dewormers. Horses that have not been – or poorly – dewormed are at greatest risk for large strongyles.

REFERENCES

1. Handbook of Equine Parasite Control, Second Edition. Martin K. Nielsen and Craig R. Reinemeyer. © 2018 John Wiley & Sons, Inc. Published 2018 by John Wiley & Sons, Inc