ABSTRACT
OBJECTIVE: Review 103 cases of presumed tick envenomation in horses. DESIGN: Retrospective study. METHOD: 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. CONCLUSION: 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.
Subject(s)
Arthropod Venoms/toxicity , Horse Diseases/mortality , Ixodes , Tick Toxicoses/veterinary , Animals , Female , Horses , Male , Retrospective Studies , Risk Factors , Seasons , Tick Infestations/mortality , Tick Infestations/veterinary , Tick Toxicoses/mortalityABSTRACT
Toxins have been shown to present in the salivary glands, whole body extracts, and eggs of ticks. They cause histological lesions in the skin, and in various organs of tick hosts. Among toxicoses, tick paralysis is of the greatest medical and veterinary importance. Toxins are secreted by cells "b" of acinus II in salivary glands during tick feeding.
