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

Abstract

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.

Experimental Applications and Factors Involved in Validating Thermal Windows Using Infrared Thermography to Assess the Health and Thermostability of Laboratory Animals

“…Figure 5 illustrates the vascularization of the eye, especially two large arteries—the arteria supraorbitalis and angularis occuli—that are ramifications of the facial artery which supplies circulation to this region. One aspect that must be emphasized is that the arteria angularis occuli is innervated by the facial nerve [ 54 ], so that zone responds sensitively to the predominant autonomous tone during diverse stimuli that is applied to species such as large ruminants [ 51 ], dogs ( Canis lupus familiaris ) [ 67 ], and equines [ 68 ].…”

Handling and Physiological Aspects of the Dual-Purpose Water Buffalo Production System in the Mexican Humid Tropics

“…Research has documented that 3.4% of female buffaloes manifest estrous behavior and that over 60% have what is called “silent estrus” [ 8 , 15 ]; thus, some ranches have implemented fixed-time reproductive protocols that foster genetic improvement by responding to the physiological characteristics of female buffaloes if no male capable of identifying estrus is available ( Figure 3 ). In addition to this, non-invasive tools such as infrared thermography have been used in the detection of estrus due to the changes presented in the vulva prior to ovulation, which could be an efficient and safe indicator of estrus [ 16 , 17 , 18 , 19 ].…”

Description of Four Dual-Purpose River Buffalo (Bubalus bubalis) Farms in Tropical Wetlands in Mexico. Part 1: Social Aspects, Herd Distribution, Feeding, Reproductive, and Genetic Management

“…Production units in countries like Colombia, Argentina, and Venezuela have successfully implemented more complex methods of assisted reproduction, such as embryo transfer, the use of sexed semen, thermal monitoring to better understand changes during estrus, and technologies that allow the detection of sick animals without clinical signs [42,43]. There are even cases where genomic testing is applied to identify the animals with the greatest genetic potential.…”