Fungal Skin Infection in a cat

Billy is a 6 month old Birman male cat. His owner noticed that he had multifocal circular areas of alopecia (hair loss) with broken hairs at the periphery. The surrounding skin was also quite scaly. He was not itchy. His owner’s son also had a red circular lesion on his arm.

Hair from the periphery of the lesion was collected and placed in a dermatophyte test medium (DTM). The test takes 7 days to read so in the interim treatment with antibiotics and an antifungal shampoo was prescribed.

At 7 days the DTM was read- it had a growth of flat white colonies producing a red colour. This is a positive for ringworm.

Normal DTM on the right; colour change and colony growth on DTM with ringworm on the left.

Ringworm is a misnomer as the actual infective agent is a fungus, not a worm.The fungi that infect the hair follicle usually involve species of the genera Microsporum or Trichophyton. These are either transmitted from the soil or from other infected animals.

Infection affects the hair follicles leading to hair crusting and loss.Affected animals usually recover spontaneously after a period of several weeks but chronic infection may occur.

It’s important to note that cats may develop a carrier status in the absence of clinically apparent lesions and represent an insidious source of contamination for dogs. In this case Billy was from a single cat household with no dogs.

Billy responded well to the topical antifungal treatment so no further medications were required. Environmental decontamination was essential due to dispersal of infected hairs from Billy- thorough cleaning with disinfectants and vacuum cleaning, this was to be repeated on a number of occasions.

It was also advised that Billy’s owner’s son see a Dermatologist as he would be a potential source of re-infection for Billy.

Billy is doing very well and has been lesion free for 2 months!