Infrared (IR) thermography is a noninvasive diagnostic screening tool that does not require handling or restraint of an animal. Physiologic or pathologic processes involving changes in surface temperature may be evaluated using this technique. This modern
method provides real-time, instantaneous visual images with measurements of surface temperatures over a greater distance.
The first medical application of "thermography" was by Hippocrates (ca. 460-375 BC), who used thin layers of mud for his temperature measurements, similar to modern thermography. An area of great heat emission caused an area of the mud to dry first, and thus a "hot spot" was detected. 29 It was not until the mid-eighteenth century, however, that temperature scales were developed by Fahrenheit, Reaumur, and Celsius, and not tmtil 1800 that Sir William Herschel discovered infrared rays distinguishable from visible light. The first detector was constructed in 1830.
Infrared thermography has been used for skin temperature measurement in human medicine since 1960 and for the early detection of diseases since 1980, mainly pathologic processes such as pain in the lumbosacral region, intervertebral disc prolapse, spinal cord lesion, traumatic lesions, fractures, neuropathology, cardiovascular diseases ( especially impairment of blood supply), lateral effects of heat or frost burns, and long-term monitoring of skin transplants. In wildlife biology, IR thermography has been used since the mid-1940s for detecting and monitoring mammal and bird species. To some degree the method could even be used successfully in animal censuses. In veterinary medicine this technique has been used on farm and companion animals since the late 1950s. The most advanced field is that of equine medicine. Eulenberger and Kampfer first recommended the use of IR thermography in zoo and wild animal medicine.
Phillips performed the first large-scale comparative studies on thermoregulation in zoo animals with the aid of infrared thermography. Both studies employed traditional, carbon dioxide (CO2)-coolec-systems, which proved to be difficult to use under routine zoo and wildlife conditions. Hilsberg first used IR thermography extensively with modern equipment in zoo medicine.