Generally speaking, a cat’s body temperature will have a fluctuation range. It is normal for the body temperature to rise within a certain range. However, if it exceeds a certain limit or lasts for too long, it should be taken seriously. What causes high fever in cats? There are many, which require careful identification by owners and doctors.

1. Types of elevated body temperature

1. True fever

True fever refers to fever produced by endogenous pyrogens. Endogenous pyrogens are mainly cytokines, such as interleukin, tumor necrosis factor, interferon, etc. They are produced by using a variety of immune active cells under the stimulation of immune responses to different antigens or pathogenic factors. Cytokines have many functions such as immune regulation, stimulating hematopoiesis, anti-virus, and anti-tumor. However, the above-mentioned cytokines It also has strong pro-inflammatory activity and can act on the body temperature regulation center to cause fever in the body.

　2. Insufficient heat dissipation

Insufficient heat dissipation refers to heat shock. Heat shock is a stress response, which refers to the defense adaptation response characterized by changes in gene expression that a biological organism exhibits under heat stress (or other stress) conditions. For heat shock response. A group of proteins that are newly synthesized or increased during heat stress (or other stress) are called heat shock proteins. Heat shock response also has the basic characteristics of stress response, namely non-specificity and defense adaptability.

3. Increase in running body temperature

Exercise will also increase the cat's body temperature. Generally, after the cat comes back from the outdoors, or after the cat plays and runs, the owner trains the cat, which will also temporarily increase the cat's body temperature. In other respects, pathological movements caused by cat convulsions and epilepsy can also increase body temperature.

4. Pathological or drug-induced

For example, damage to the anterior or surrounding hypothalamus, or some hypermetabolic diseases. At the same time, some external heat sources such as bacterial infections and inflammatory irritants can also increase the cat's body temperature.

2. Three stages of fever caused by pyrogens

1. Body temperature rising period

This is the early stage of fever. The cat shows peripheral vasoconstriction, reduced skin blood flow, and lowered skin temperature. Due to the excitement of the chill center, the skeletal muscles involuntarily contract, shivering occurs, and the body temperature continues to rise until it reaches a new set point. until level.

　2. High temperature duration

Also known as the extreme heat period, during which the cat’s chills stop, blood vessels dilate, blood flow accelerates, breathing and heartbeat rates increase, and substance metabolism increases. Sometimes the high temperature can last for several days.

3. Body temperature drop period

Also known as the antipyretic period. As the cause of the disease is eliminated, the heat source in the blood decreases or disappears, and the set point of the body temperature center returns to normal levels. Cats in this stageHeat dissipation is enhanced, heat production is reduced, body temperature is lowered, the cat sweats a lot, urine output increases, and the body temperature slowly drops to normal levels within a few days or hours.

3. The relationship between the thermoregulatory control system and body temperature

The body temperature set point increases when fever begins and decreases when fever ends. When the body temperature regulation control system detects that the set point and body temperature are out of tune, it mobilizes the body's rich receptor responses to correct the mismatch. These reactions include tremors, cutaneous vasoconstriction, etc. at the beginning, and end with sweating, cutaneous vasodilation, etc.

4. Physiological mechanism of body damage caused by high fever

a) True fever causes changes in the hypothalamic body temperature set point, which is most likely mediated by the endogenous pyrogen interleukin I;

b) Non-febrile hyperthermia does not change the hypothalamic temperature set point;

　c) A sustained body core temperature >41.1℃ can cause multiple organ damage, and a core temperature reaching 42.7℃ can cause death;

d) The main pathophysiological process of heat shock is related to temperature damage, including cell necrosis, hypoxemia, and protein denaturation;

e) Heat shock and its consequences can lead to SIRS.