How can you tell if a rat has a fever?

How can you tell if a rat has a fever? - briefly

Measure the rodent’s core temperature with a rectal thermometer; normal values are 37‑39 °C, and readings above roughly 40 °C indicate a fever.

How can you tell if a rat has a fever? - in detail

Rats normally maintain a core temperature between 37.5 °C and 38.5 °C. Values above this range indicate fever and should prompt veterinary assessment.

Direct temperature measurement

• Use a calibrated digital rectal thermometer with a flexible probe.
• Lubricate the tip with sterile petroleum jelly.
• Gently restrain the animal, insert the probe 1–2 cm into the rectum, and wait for the reading to stabilize (typically 10–15 seconds).
• Record the temperature; values ≥39 °C suggest a febrile state.

Infrared thermography

• Position a handheld infrared camera 10–15 cm from the dorsal surface.
• Aim at the interscapular region, where fur is thin.
• Capture the thermal image and read the surface temperature.
• Surface readings 2–3 °C above the normal range correlate with internal fever, but confirm with rectal measurement when possible.

Behavioral and physical indicators

• Lethargy, reduced grooming, and decreased activity levels.
• Shivering or rapid breathing (tachypnea).
• Warm, moist ears or tail compared with the rest of the body.
• Loss of appetite and weight loss over several days.

Procedural considerations

• Perform measurements in a quiet environment to minimize stress, which can artificially elevate temperature.
• Use a consistent time of day for repeated checks, as circadian rhythms cause minor fluctuations.
• Clean the thermometer probe with alcohol between animals to prevent cross‑contamination.
• If fever persists for more than 24 hours or is accompanied by other clinical signs, initiate diagnostic work‑up (blood panel, culture, imaging) and consult a veterinarian.

Combining precise temperature data with observable signs provides a reliable assessment of febrile conditions in rodents.