Measuring pain-perception and behavior of laminitic horses after treatment (with addition of intramuscular Botox).

Abstract

Abstract Objective: Laminitis in the horse causes failure of the distal phalanx to maintain its attachment to the lamellae of the inner hoof wall. Also the constant traction of the deep digital flexor tendon on the distal phalanx can cause the distal phalanx bone to rotate. These changes cause unrelenting pain and a characteristic lameness (Pollit 2004) The aim of this study was to investigate whether treating acute laminitis following a treatment protocol, in addition of injecting Clostridium botulinum toxin type A (Botox®) in the muscle belly of the deep digital flexor muscle, will lead to a substantial pain relief and thus an increase in comfort of the horse, resulting in a decrease in free-cortisol concentrations in saliva, and a lower result in composite-pain-score after treatment. Method: Literature research has led to a behavior protocol to measure pain-perception and behavior in the horse suffering from laminitis. Also a protocol for cortisol determination was developed to indicate the amount of stress the horse experiences. Two groups of horses was included in the study. A control group of ten healthy warmblood horses was used to determine base-cortisol values in plasma (total-cortisol concentration) and saliva (free-cortisol concentration). In the treatment group, two horses suffering from acute laminitis were included. They were treated for laminitis following a protocol, with addition of intramuscular bilateral Botox®. At specific days post treatment (d0, d3, d7, d14) cortisol was measured in plasma and saliva, and they were scored following a composite-pain-score. Results: In contrast to earlier findings (Van der Kolk et al. 2001), we were unable to find normally distributed values of salivary cortisol in healthy horses. Cortisol-concentrations in plasma on the other hand, were indeed normally distributed. Patient I showed a nice decrease of plasma and salivary cortisol at day 3 and day 7. However, at day 14 there was an extreme rise in both plasma and salivary cortisol. Also the pain-score showed a decrease in the first days, and rising at day 14. Patient II showed an increase of both plasma and salivary cortisol at day 3, however, at day 7 and 14 it decreased back to normal. The pain-score on the other hand, showed higher scores at day 14. Conclusion: Both patients showed a decrease in cortisol-concentration after treatment. Unfortunately, the group was small (n=2) and there were underlying illnesses present in these horses that very likely might have influenced our results. Also the pain scores were influenced in this way. To reveal the value of cortisol-determination in monitoring laminitic patients, more research has to be done in which more patients are involved and circumstances can be more standardized.