130 Investigation of age, status, season, and sex on equine parasitic load in a university program

Abstract

Strongyles are nematode parasites that can damage the horse's large intestine and cecum and cause symptoms of colic, anemia, and weight loss. Sixty-four horses from the University of Connecticut campus were used to study parasitic shedding patterns, to determine if there was a seasonal, age, sex or work status effect. Horses were assigned to different statuses based on living and exercise situations. The goal of analyses was to assess whether there was a change in parasite count over time, and whether horse age, status and sex had any effect on parasite count. Fecal samples of all horses were collected in March and October for 5 years. Fecal flotation testing was done to evaluate strongyle eggs per gram (EPG). Zero-inflated (ZI), negative binomial mixed effects models were used to evaluate changes in parasite counts over time. Both conditional (nonzero parasite counts) and ZI components were adjusted for status, age, sex, and the interaction of status and year. Horse ID was treated as a random effect, to account for repeated measurements. No sex effect on parasitic load was found with either the conditional or ZI models. Similarly, neither status norseason were significantly associated statistically with parasite counts. Initial age did have an effect on conditional parasite counts, with regression results suggesting that as age increased, parasite counts decreased. Although we have some evidence of declining parasite loads at UConn, this effect was only significant for spring sampling. Fall sampling occurred after the horses had been turned out over the summer, so perhaps they are then at greater risk for getting a heavier parasite load. The decline over the years in the March data could be due to the implementation of a parasitic control protocol by barn management 4 years into the study. This study appears to agree with other studies in that older horses are less affected by internal parasites than their younger counterparts. The parasitic control protocol implemented by barn management appears to have had a positive effect on horses in the spring. More research is needed to determine if this protocol will eventually have an effect on the fall as well.