title: Biphasic appearance of corticated and decorticated ascarid egg shedding in untreated horse foals.
abstract: Parascaris spp. infects foals worldwide and may cause airway inflammation in addition to small intestinal impaction and rupture. It is observed that acquired immunity eliminates ascarid burdens beginning at about 6 months of age, and current evidence suggests that a single parasite generation propagates in each foal crop. The purpose of this study was to monitor natural parasitic infections in untreated mixed breed horse foals over the course of 0-300 days of age. Fecal samples were collected monthly from all foals born in 2014 (n=13), beginning July 2014 through February 2015. Fecal egg counts (FECs) were performed in triplicates using the Mini-FLOTAC method. The foals were necropsied between 154 and 298 days of age and all intestinal ascarid were collected and identified to stage. Ascarid FECs exhibited a biphasic distribution with an initial peak at 91-120 days of age and, after a steady decline, a second, smaller peak at 241-300 days of age. Numbers of corticated and decorticated ascarid eggs were compared, with decorticated FECs remaining consistently low with a slight increase directly after the first corticated FEC peak. Overall, 4.36% of the total ascarid eggs counted were decorticated. Ascarid FECs showed a sharp peak in September, declined, and then steadily increased beginning in December and continuing through February. Upon necropsy, moderate to high number of ascarid specimens were recovered from foals between 8 and 10 months of age, coinciding with the second peak for the FECs. Eleven of the 13 foals harbored immature ascarid stages indicating a recent reinfection. However, these data demonstrates that apparently a second, smaller wave of infection is present in 8-10 month old foals. It may be of value to monitor egg counts in this age group to make sure that all parasite categories are well controlled.
authors.affiliation: M.H Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Donoghue
authors.affiliation: M.H Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, USA.
authors.forename: E T
authors.initials: ET
authors.lastname: Lyons
authors.affiliation: M.H Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Bellaw
authors.affiliation: M.H Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington, USA. Electronic address: martin.nielsen@uky.edu.
authors.forename: M K
authors.initials: MK
authors.lastname: Nielsen
mesh_terms: D000818:Animals; D017191:Ascaridida Infections / Q000469:parasitology / Q000662:veterinary*; D001199:Ascaridoidea; D005243:Feces / Q000469:parasitology; D006734:Horse Diseases / Q000469:parasitology*; D006736:Horses; D010063:Ovum / Q000166:cytology*; D010270:Parasite Egg Count
keywords: Corticated; Decorticated; Egg count; Horse foals; Parascaris spp.