Texas Equine Veterinary Association

• 17 • Habronema... not just a simple problem anymore!! Dr. Easterwood is a native Texan who obtained her undergraduate, Masters, and DVM degrees from Texas A&M University. Aer graduating from veterinary school in 1995, she completed a private practice equine internship at Las Colinas Veterinary Hospital in Las Colinas, Texas. She remained in private equine practice for an additional 9 years before returning to Texas A&M to start a Large Animal Internal Medicine Residency in 2005. Upon completion of the residency in 2008, she has remained on faculty in the Veterinary Medical Teaching Hospital. She has a strong interest in periocular squamous cell carcinoma. She serves as one of the official show veterinarians for the Houston Livestock Show and Rodeo. Dr. Easterwood is passionate about supporting our Military, and volunteers for several causes on campus including Horses for Heroes, and Aggies Support the USO. She is an active member of the American Association of Equine Practitioners, TVMA, AVMA, TEVA and AQHA. by Leslie Easterwood, DVM Texas A&M University Habronema lesions became pretty uncommon aer ivermectin was introduced as an animal anthelmintic in the early 1980s. ere was no resistance at the time, and for many years habronema became a lesion that was rarely seen in developed countries. e migrating larvae were easily killed by systemic doses of ivermectin. In the early 2000s though, we started to see a reemergence of this pesky problem and resistance to ivermectin was seen as the reason for the resurgence. Moxidectin was introduced to the equine market in 1997, but was never proven to be as effective against migrating larvae as ivermectin was when it was introduced to the market. Perhaps the developed resistance to ivermectin was a broader resistance to the class of Avermectins, thus limiting the effectiveness of moxidectin from the start. Adult Habronema spp. inhabit the stomachs of horses as fibrous nodules of the stomach lining. ey produce eggs that are passed in the feces. ese eggs hatch soon aer defecation and become L1 larvae that are eaten by common fly species larvae (stable and house). e adult fly emerges already infected with the habronema larvae. While feeding, the flies deposit the habronema larvae around the nose or lips of the horse. e horse ingests the larvae to start the cycle over. Figure 1: Habronema larvae from a scraping (diff quick stain) Figure 2: Classic medial canthus habronema lesion

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