New data shows tapeworm prevalence on West Coast farms as 17.3% in California, 36.5% in Oregon and 25.3% in Washington. A 2003 study in equine parasitology by Craig Reinemeyer, DVM, PhD, of East Tennessee Clinical Research, uncovered the high prevalence of equine tapeworms throughout the United States. That original study indicated a lower risk of tapeworm exposure on the Pacific Coast compared to other areas of the country. To get a better representation of the prevalence of tapeworm exposure, the study was recently repeated, using more than 300 farms and 600 samples from across the three Western states.

These new figures confirm that the tapeworm poses a medical threat to horses all over the United States, not just the Eastern and Midwestern regions.

“This new research helps answer many questions about tapeworm prevalence in the western United States,” said Bobby Cowles, DMV, MS, MBA, of Pfizer Animal Health. “Understanding the life cycle of the tapeworm, where it resides, and the severe impact it can have on the horse is the first step to actively dealing with this potential medical problem.”

Research suggests that oribatid mites may be the key link to the tapeworm threat. As the intermediate hosts to Anoplocephala perfoliata–the most common species of tapeworm infecting horses in the United States–these insects are highly prevalent worldwide. As microscopic decomposers, these mysterious mites can exist by the thousands or even millions per square meter of soil. Any horse that grazes on pastures, eats hay, or is bedded with straw or wood products is likely exposed to oribatid mites, which could potentially translate into tapeworm infections