On-farm Tapeworm Testing in Horses

Abstract Text: The incidence of tapeworm infection in horses was investigated on nine farms in North Carolina and one in Virginia. Two of the North Carolina farms were used in three replicates. A total of 602 horses at least one year of age were used (321 individuals, 281 were replicates; 157 females, 164 males) in the Summer, Fall and Winter seasons. Individuals averaged 12.1 ± 0.4 years of age and 541.8 ± 7.0 kg body weight. Animals were treated with commercial horse anthelmintics containing ivermectin and praziquantel (Zimecterin Gold^®; n=412; 8 farms including those replicated; and Equimax^TM; n=190; 4 farms) as labeled for BW measured by equine weight tape plus 15% with doses rounded up to the nearest 22.7 kg (50 lb). At treatment (d 0) and 24 hr later (d 1), fecal samples were collected after defecation for tapeworm fecal egg count (FEC) using the Modified McMasters technique with a sensitivity of 8 eggs per gram (epg). Descriptive statistics were used to report data. On d 0, 1.4 ± 0.01% of horses were positive for tapeworm eggs, whereas on d 1, 20.6 ± 1.7% were positive. Positive horses were found on 30% of farms on d 0 and 60% of farms on d 1. This data suggests that tapeworm infections are common on horse farms, but that most horses do not have infections or have undetectable infections.  Furthermore, these data demonstrate that sensitivity of detection for tapeworms via fecal exam is greatly increased by testing one day after treatment.   

Keywords: Tapeworms, horses, FEC