Caregiver Placebo Effect on Zoo-Animal Welfare: Application of a Pressure Walkway System for Objective Evaluation of Lameness in a Zoo Setting
In domestic animals, force plates and pressure-sensitive walkways have been used to characterize normal and abnormal gait variables,5,6 yet this technology rarely has been applied in nondomestic animals.3,4,7 The use of gait analysis technology provides an objective assessment of analgesic efficacy and is a valuable tool for characterizing the impact of caregiver and veterinarian bias on lameness scoring in domestic animals.2,8 In pets, an owner or caregiver placebo effect can profoundly affect interpretation of analgesic efficacy and lead to false assumptions on alleviation of pain. Zoo clinicians often heavily depend on the interpretations of animal care staff to assess treatment efficacy, a scenario inherently prone to misinterpretations and bias. Furthermore, with medical advances, geriatric care of zoo animals with degenerative joint disease is increasingly prevalent. Biased assessments of analgesic efficacy can significantly impact quality of life and appropriate welfare decisions. Pressure-sensitive walkway technology provides an opportunity to objectively assess some of these welfare considerations. A 10-ft-long Tekscan® Walkway™ 7 System was installed to objectively evaluate lameness concerns and analgesic efficacy in nondomestic animals. A custom-built housing for the system has facilitated use in a variety of species. Stance time, stride time, stride length, stride velocity, maximum force, and maximum peak pressure can be calculated to detect lameness-associated alterations in gait. In addition, static weight distribution across the plantar foot surface can be a useful tool for comparisons between limbs in animals in a stationary stance. Species-specific data from sound animals must be established, but with this in place, prospective research on the response to analgesic efficacy is possible. Normal values in Humboldt penguins have been reported1 as proof of concept, and authors are expanding to additional species. These normal values have allowed detection and quantification of lameness and gait alterations in clinically abnormal specimens, followed by controlled objective studies on the efficacy of analgesic therapies.
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