What is the main clinical sign associated with a diagnosis of dermatophytosis in cattle?

Dermatophytosis, commonly known as ringworm, is a fungal infection that often affects the skin of cattle. The primary clinical sign associated with dermatophytosis is non-pruritic alopecia, which manifests as patches of hair loss without significant itching or irritation. This is typically due to the infection disrupting the normal hair follicle and skin function, leading to the formation of alopecic, or bald, areas on the skin where hair has fallen out, often appearing circular in shape.

While pustules may be present in some skin infections, they are not a hallmark of dermatophytosis. Fever is a systemic sign that is more commonly associated with infections that elicit a significant inflammatory response, which is not characteristic of dermatophytosis. Polyuria pertains to changes in urination and is not related to skin conditions. Thus, the identification of alopecia as a main sign is crucial for diagnosing dermatophytosis in cattle.