Assessment of Pain and Inflammation in Domestic Animals Using Infrared Thermography: A Narrative Review

Abstract

Pain assessment in domestic animals has gained importance in recent years due to the recognition of the physiological, behavioral, and endocrine consequences of acute pain on animal production, welfare, and animal model validity. Current approaches to identifying acute pain mainly rely on behavioral-based scales, quantifying pain-related biomarkers, and the use of devices monitoring sympathetic activity. Infrared thermography is an alternative that could be used to correlate the changes in the superficial temperature with other tools and thus be an additional or alternate acute pain assessment marker. Moreover, its non-invasiveness and the objective nature of its readout make it potentially very valuable. However, at the current time, it is not in widespread use as an assessment strategy. The present review discusses scientific evidence for infrared thermography as a tool to evaluate pain, limiting its use to monitor acute pain in pathological processes and invasive procedures, as well as its use for perioperative monitoring in domestic animals.

Correlation of temperature-sensing microchip and rectal temperature measurements in cats

“…Hyperthermia can be produced in rats using neurotoxic agents, which affect central thermoregulation ( 57 ). Also, nociceptive stimuli can cause temperature changes, due to activation of the sympathetic adrenomedullary system [released catecholamines activate adrenoceptors in vascular smooth muscle, which alters blood flow, blood pressure, heart rate and respiratory rate and can alter both peripheral and core temperature ( 58 )]. The Bland–Altman method alone cannot determine whether the 95% limits of agreement set are acceptable or not.…”

Application of Infrared Thermography in the Rehabilitation of Patients in Veterinary Medicine

“…IRT is a method that directly evaluates the amount of heat radiation emitted from a physical body and, in mammals, is associated with thermoregulatory mechanisms [ 30 , 31 ]. In veterinary medicine, it has been used to identify superficial lesions due to the local inflammatory process taking place [ 9 , 13 , 32 ]. Most veterinary patients referred to physiotherapy have sustained inflammatory and painful conditions in the musculoskeletal system, hampering their quality of life.…”

“…Figure 1 shows the effect of the inflammatory response in a canine patient with a radioulnar fracture. Whittaker et al [ 13 ] mention that during an inflammatory and chronic pain process, such as osteoarthritis (OA) or CCLR, immune cells such as neutrophils and macrophages release substances and chemicals such as interleukin (IL)-1, IL-10, IL-6, tumor necrosis factor-α (TNF-α) and prostaglandin F 2α (PGF 2α ); these are known as proinflammatory mediators since they increase local blood flow and, consequently, the surface temperature detected with IRT.…”

“…Examples of these events are lesions in dermal or muscular tissue, and bone, ligament, joint, and tendon injuries [ 9 , 10 , 11 , 12 ]. After tissue damage, proinflammatory mediators are released, causing the vasodilation of capillaries, venules, or arterioles, with a subsequent increase in local temperature [ 13 , 14 , 15 ]. On the other hand, local hypothermia can be seen in patients with vascular compromise and ischemia issues [ 16 , 17 ].…”

Thermographic Profiles in Livestock Systems under Full Sun and Shaded Pastures during an Extreme Climate Event in the Eastern Amazon, Brazil: El Niño of 2023

“…Among the technologies used to investigate animal comfort and environmental conditions quickly, non-invasively and with reliable and replicable results, monitoring using near-infrared thermography has been gaining ground, with applications in different areas of scientific knowledge, such as early diagnosis of diseases, non-invasive assessment of rectal temperature, determination of animal thermal stress and thermal characterization of the environment in which they live [ 23 , 24 ]. The radiometric imaging allow data to be obtained by evaluating targets such as the surface of animals and correlating them with the production systems studied [ 25 , 26 , 27 , 28 , 29 , 30 ].…”