What physical symptom can indicate a severe case of distemper?

The hardening of footpads is an important physical symptom that can indicate a severe case of distemper. In canine distemper, the virus can affect multiple systems within the body, leading to respiratory and neurological symptoms, as well as affecting the skin. One characteristic manifestation is the hardening of the footpads and nose, which is sometimes referred to as "hard pad disease." This occurs due to the viral infection leading to changes in the keratin in these areas, resulting in a thickened and sometimes cracked appearance of the pads.

Recognizing this symptom is crucial because it signifies a more advanced stage of the disease, requiring immediate veterinary attention. The other symptoms mentioned, while they may be associated with distemper or other health issues, do not specifically indicate the severity of the disease in the same way that the hardening of footpads does.