title: Retrospective study of 103 presumed cases of tick (Ixodes holocyclus) envenomation in the horse.
abstract: OBJECTIVE
  Review 103 cases of presumed tick envenomation in horses.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Variables, including date of presentation, age, breed, weight, presence of ticks, gait and respiration scores, duration of recumbency, treatment, outcome and complications were recorded. A series of univariable screening tests were performed and used in a multivariable logistic regression model.
  
  
  RESULTS
  There were a total of 103 cases affecting 10 breeds, aged between 1 week and 18 years of age. Horses >6 months old and weighing >100 kg had a higher odds of death than those <6 months old and <100 kg. Cases were seen from North Queensland to the central coast of New South Wales and were more likely to present in the warmer months. There was no association between the number of ticks found on an animal and death. Horses with a higher respiratory score had higher odds of dying, but there was no association between gait score and survival. Horses recumbent >120 h after presentation had higher odds of dying. Complications were reported in 35% of horses. The odds ratio for survival was higher for horses receiving >0.5 mL/kg of tick antiserum. Overall, 74% of horses survived. Multivariable modelling was limited by the small sample size.
  
  
  CONCLUSIONS
  In general, tick envenomation in horses follows the geographic distribution of Ixodes holocyclus. Tick antiserum administered at >0.5 mL/kg increases the odds of survival. It would appear that the complications associated with managing a recumbent horse increase the odds of death.
authors.affiliation: Research and Clinical Training Unit, Veterinary Teaching Hospital Camden, The University of Sydney, New South Wales, Australia.
authors.forename: M
authors.initials: M
authors.lastname: Ruppin
authors.forename: S
authors.initials: S
authors.lastname: Sullivan
authors.forename: F
authors.initials: F
authors.lastname: Condon
authors.forename: N
authors.initials: N
authors.lastname: Perkins
authors.forename: L
authors.initials: L
authors.lastname: Lee
authors.forename: L B
authors.initials: LB
authors.lastname: Jeffcott
authors.forename: A J
authors.initials: AJ
authors.lastname: Dart
mesh_terms: D000818:Animals; D001180:Arthropod Venoms / Q000633:toxicity*; D005260:Female; D006734:Horse Diseases / Q000401:mortality*; D006736:Horses; D018884:Ixodes; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D013984:Tick Infestations / Q000401:mortality / Q000662:veterinary; D013986:Tick Toxicoses / Q000401:mortality / Q000662:veterinary*
chemical_list: D001180:Arthropod Venoms; C038423:holocyclotoxin