Pyrexia
What is the specific cause of pyrexia? What is the temperature at which we call it pyrexia?
An underlying infection (bacterial, viral, parasitic, fungal) causing a release of pyrogenic cytokines
>103 °F
What are the two causes of hyperthermia?
Exertional and Environmental
Exertional hyperthermia occurs due to intense physical exertion that exceeds the body's cooling methods (panting, vasodilation, sweating through paw pads). Environmental hyperthermia occurs when the outside temperature is too high, or there is a lack of ventilation.
What is the body's normal "set point?" Is the set point changed when there is pyrexia?
Normal: 99-102.5 °F
Yes! The set point raises when there is pyrexia, typically to 103 °F or higher.
Is the body's "set point" changed when there is hyperthermia?
No! Hyperthermia occurs because the body has failed to stay within the set point. The set point itself does not change.
What part of the brain regulates temperature control, and how does it elevate the body's "set point?"
Hypothalamus
The hypothalamus has a set point for temperature (usually 99-102.5 F), and triggers cooling or warming to maintain that set point. When pyrogenic cytokines are released, the hypothalamus will release prostaglandin E2 which elevates the body's set temperature. This is done to create a hostile environment for bacteria or viruses to live in.
What causes the body's temperature control to fail to stay within the set point?
The environmental temperature or degree of exertion exceeds the body's own cooling abilities - it isn't enough to maintain body temp within the set point.
What are some treatments commonly used to bring fever down?
NSAIDs to reduce inflammation (dog: Carprofen, Meloxicam; cat: Onsior)
Antibiotics if determine a bacterial cause
Cooling methods like a fan, cool damp cloths, or spraying alcohol on the paw pads (stop cooling at 103 F to prevent hypothermia)
Fluid therapy
What breed is prone to developing hyperthermia and why?
Brachycephalics
Their anatomy (elongated soft palate, everted saccules, stenotic nares, hypoplastic trachea) makes it difficult to breathe and pant correctly to dissipate heat. This is why during hot summer months, brachycephalics should always be kept in the AC and only be taken outside for short walks. Remember, they aren't just more prone to environmental hyperthermia - also exertional!
What is fever/pyrexia of unknown origin?
A persistently high body temperature (lasts for a few days) with no identified infectious cause despite diagnostics. It is usually due to immune-mediated diseases or certain cancers like lymphoma or multiple myeloma that are causing chronic inflammation. Diagnosis often requires a full workup of CBC/Chem, radiographs, ultrasounds to rule out other causes.
What is the body temperature that we start to worry about neurological issues?
106°F or higher. Above this temperature the animal may show a depressed mentation, ataxia, tremors, and seizures.