Assessing the Association Between Hoof Thermography and Hoof Doppler Ultrasonography for the Diagnosis of Lameness in Horses

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

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.

Pathophysiology of Fever and Application of Infrared Thermography (IRT) in the Detection of Sick Domestic Animals: Recent Advances

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

Advances in infrared thermography: Surgical aspects, vascular changes, and pain monitoring in veterinary medicine

One of the main functions of infrared thermography (IRT) consists in detecting temperature changes in organisms caused by variations in surface blood circulation. IRT is a useful tool that has been used mainly as a diagnostic method for various stress-causing pathologies, though recent suggestions indicate that it can be used to assess the block quality of certain body regions. In the field of anaesthesiology, IRT has been applied to brachial and epidural blocks, while in algology, changes in surface blood circulation associated with sympathetic activity have been investigated. Thermography has also been employed to complement pain level scales based on the facial expressions of patients in critical condition, or after surgery. In addition, it has been used as a tool in research designed to evaluate different surgical procedures in human medicine, as in the case of surgical burrs for placing dental implants, where IRT helps assess the degree of heating associated with bone devascularisation, reduction in vascular perfusion as a consequence of stroke, and changes in the autonomous nervous system, or the degree of vascular changes in flaps applied to burn patients. In veterinary medicine, thermography has brought several benefits for animals in terms of evaluating lesions, diseases, and surgical procedures. The aim of this review is to evaluate how IRT can be used as a tool in surgical procedures, cases of vascular change, and pain monitoring in veterinary medicine with an emphasis on small animals.

The utility of infrared thermography for evaluating lameness attributable to bacterial chondronecrosis with osteomyelitis

Bacterial chondronecrosis with osteomyelitis (BCO) is a leading cause of lameness in broilers. Infrared thermography (IRT) is a noninvasive technique for measuring infrared radiation from an object and can be used to evaluate clinical health. Two replicated studies compared the effect of light intensity on broilers grown on a wire flooring model that experimentally increased their susceptibility to and incidence of BCO lameness. Day-of-hatch male broiler chickens were placed into 6 pens on wood shavings litter, and at 1 wk one of 3 light intensity treatments (2, 5, or 10 lux) was allotted. At 4 wk half of the population from each pen was moved to a pen with wire flooring and the same light intensity. At 1, 4, 5, and 8 wk, an IRT image of the legs of 5 clinically healthy broilers from each pen was taken. The right and left proximal femora and tibiae of sound and lame broilers were scored for femoral head necrosis (FHN) and tibial head necrosis (THN) lesion severity. There were minimal effects of light intensity and flooring. In Study 1, but not Study 2, broilers on wire flooring weighed less on day 38 (P = 0.007) and days 57 to 58 (P = 0.003) compared to those on litter. The proportion of broilers that became lame on wire flooring was 52% in Study 1 and 14% in Study 2. The proportion of sound broilers from litter and wire flooring pens with subclinical signs of BCO in their right or left proximal growth plates was over 45% for FHN and 92% for THN, and lame broilers had more severe (P < 0.0001) FHN and THN compared to sound broilers. IRT surface temperatures of the hock joint, shank, and foot were consistently lower (P < 0.0001) in broilers that became lame when compared to sound. Therefore, IRT surface temperatures of broiler leg regions may be useful for detecting lesions attributed to BCO.