PREVALENCE OF STRONGYLE AND ASCARID EGG SHEDDING BY HORSES IN THE UNITED STATES, 1998-1999

total of 985 operations participated in the parasite portion of the study. The number of horses sampled per operation was based on a sliding scale with a maximum of 20 sampled on operations with 50 or more resident horses. Fecal samples were shipped overnight to the National Veterinary Services Laboratories (NVSL) in Ames, Iowa. A modified Stoll's technique using Sheather's solution was used to perform a fecal flotation examination on each sample and the number of eggs in one gram of feces were counted. Eggs from large and small strongyles cannot be differentiated by fecal flotation alone and are thus reported here as one group. Horses shedding ten to 290 strongyle eggs per gram (epg) of feces were considered as shedding at a low level. Moderate and high levels were 300 to 590 epg and 600 or more epg respectively. An operation shedding level was calculated from the average number of strongyle eggs shed among all horses sampled on each operation. All estimates are based on analysis of weighted data using SUDAAN b allowing for inference to the overall horse population in the 28 participating states. For comparison of descriptive statistics, a 90% confidence interval was used [point