Diagnosis of Ringworm in Cattle

Ringworm lesions are usually easy to recognise. Other dermatoses may cause similar lesions and microscopy or fungal culture is required for a definitive diagnosis.

Sample collection

Two methods can be used:

• Hair plucks from fresh lesions.
• Scrapings of crust, hair and scale using a scalpel blade.

Material collected is placed in a sealed envelope and submitted to the laboratory. Samples collected by the above methods are suitable for direct microscopy.

If culture is contemplated, swabbing the area with 70% alcohol prior to collection of material may reduce contaminants in the specimen.

Laboratory tests

• Direct microscopy: identification of the fungi
• Culture for definitive diagnosis and identification of the species involved. Culture mediums are Sabouraud’s agar, mycobiotic agar and dermatophyte test medium (DTM). In order to arrive at a conclusive answer culture time may need to be extended for as long as three weeks.

Typical ringworm lesions on the head of a calf.