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Inside the mite the egg develops into the infec- tive stage, which is essentially the head of the tapeworm. Horses eat the mites while grazing, and digest the mites, releasing the tapeworm head where it will at ach, develop, and produce mature, egg-fi lled segments.


BOTS—THEY LOOK LIKE BEES


There are three types of bot flies with


similar life cycles that infect horses, though all fi nd their way into the mouth where they burrow into the tongue and gums between the teeth. All larvae remain in the tissues ap- proximately 28 days before migrating to the stomach, where they at ach to the lining. What diff ers is the location on the horse’s body the eggs are laid and where the larvae at ach in the horse’s stomach.


◗ Gasterophilus intestinalis lays eggs on shoulder hair and front legs near knees. When the horse licks the eggs they hatch and the larvae attaches to the horse’s tongue.


◗ Gasterophilus nasalis lays eggs on hair under the jaw between jawbones. Eggs hatch spontaneously aſt er 5–10 days and the larvae then burrow through tissue into the mouth.


◗ Gasterophilus hemorrhoidalis lays eggs on short hair near lips. Eggs hatch spontaneously and either burrow into or migrate to the mouth. T e larvae can also travel to the rectum to at ach and may cause rectal prolapse.


When the larvae release their at achment,


they leave behind a small ulcer, pass out of the intestine and burrow into the soil. Aſt er two to three weeks, at the optimal temperature, the bot fl y will emerge from the soil to mate, and the female will begin laying eggs on multiple horses. By spreading the eggs among several horses, bot fl ies improve the species survival rate. Bots have nearly been exterminated in many areas due to use of ivermectin.


PINWORMS ARE A MINOR IRRITANT—UNLESS YOU’RE A HORSE


Mature female pinworms (Oxyuris equi)


crawl out of horse’s rectum at night and lay a huge number of eggs. T e substance used to glue clusters of eggs together and to the rectal opening causes itching in many horses and may result in tail rubbing. T e eggs drop off into the horse’s environment where they can be eaten to begin the life cycle again.


40 | June 2012 • WWW.TRAILBLAZERMAGAZINE.US


For more information about the best parasite control products see:


Absorbine | WF Young, p.69,100 Bimeda, p.39 Fly Armor, p.41 Horse Health USA, p.19 Smartpak Equine, p.15 VermX USA, p.37


PARASITES FOREVER? Parasites in horses have been around for


a very long time. One very signifi cant factor that aids in all parasites’ survival is the large number of eggs they produce. Despite our best eff orts to eradicate them, they are always one step ahead of us, defensively changing and adapting for continued survival. T ousands of horses have been saved by rotational deworm- ing, but parasites’ ability to adapt and survive by developing resistance to dewormers chang- es how we approach parasite management in horses today. For further information on the most up-to-date approaches to deworming your horse, see “Rethinking Our Approach to Equine Parasites,” in the March issue.


Horsemen’s Laboratory owner John Byrd, DVM, is a graduate of the Univer- sity of Illinois College of Veterinary Medicine and practiced equine medicine


for 21 years. He has extensive experience showing, racing and breeding horses and currently oversees Westbrook Board- ing Stable. Dr. Byrd created Horsemen’s Laboratory in 1992 to help horse owners protect their horses from worms by using fecal egg counts and selective deworm- ing. His wife, Becky Byrd, serves as offi ce administrator for Horsemen’s Laboratory.


Linda Clark, owner of Harris & Clark Expedi- tion, is a freelance graphic designer and writer specializing in design for print and content for web.


Linda and husband Rodger purchased two mares in foal in 1999 and boarded them at Westbrook Boarding Stable until they could bring them home. With no prior horse experience, they relied heavily on Dr. John and Becky Byrd for guidance and were “raised correctly” regarding fecal egg counts and selective deworming.


FMI


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