Ringworm in Cats: Causes, Signs, Treatment and How to Stop It Spreading

Ringworm (dermatophytosis) is a fungal skin infection, not caused by any worm despite the name. In cats, the most common causative organism is Microsporum canis, responsible for approximately 95% of feline cases. Less commonly, Microsporum gypseum (a soil organism) or Trichophyton mentagrophytes are implicated.

The dermatophyte fungi infect dead keratinised tissue: hair shafts, the outer layer of skin, and claws. They do not invade living tissue, but the host immune response to the fungus causes the inflammation and hair loss that characterise the condition.

Ringworm is one of the most common dermatological conditions seen in cats in the UAE, particularly in recently rescued or shelter-housed animals.

The classic presentation is one or more roughly circular patches of hair loss (alopecia), with broken hairs at the margins, scaling, and mild redness. Lesions most commonly appear on the face, around the ears, and on the forelimbs. The skin may appear grey and flaky, and the hair in affected areas breaks off near the skin surface rather than being pulled out at the root.

Importantly, some cats (particularly long-haired breeds such as Persians) are asymptomatic carriers. These cats carry and shed infective spores in their coat without any visible lesions. This makes ringworm challenging to control in multi-cat environments, because a clinically normal cat can be the ongoing source of infection.

Pruritus (itching) is variable. Some cats scratch affected areas; others do not appear bothered at all.

Wood's lamp examination (UV light) is a quick screening tool. Approximately 50% of M. canis strains fluoresce a distinctive apple-green colour under UV light. However, a negative Wood's lamp does not rule out ringworm, and false positives occur with topical medications and scale. It is a screening aid, not a diagnostic test.

Fungal culture on dermatophyte test medium (DTM) is the gold standard. Affected hairs are plucked from the margins of lesions and placed on culture medium, which changes colour (from amber to red) as the fungus grows. Results take 10 to 14 days, but this is the most reliable method for confirmation and species identification.

Trichogram, which involves microscopic examination of plucked hairs, can identify fungal spores faster but is less sensitive. PCR-based testing is emerging as a rapid, sensitive diagnostic option and is available in some referral laboratories.

M. canis is highly contagious to people. Human infection presents as itchy, circular, red and scaly plaques most commonly on exposed skin areas such as the arms, face, and neck. The lesions expand outward as the fungus spreads, creating the classic ring appearance.

Children, elderly individuals, and immunocompromised people are at highest risk of infection and may develop more extensive or persistent disease. Anyone handling a cat with suspected or confirmed ringworm should wear disposable gloves and wash hands thoroughly after contact.

Infected cats should be isolated from other animals and from vulnerable people in the household until treatment is underway and the infection is confirmed to be responding.

Treatment requires both topical and, in most cases, systemic antifungal therapy, as well as thorough environmental decontamination. Stopping one element of treatment while continuing others risks treatment failure.

Topical therapy: twice-weekly lime sulphur dips (diluted 1:16 with water) or twice-weekly miconazole/chlorhexidine shampoo are the most evidence-supported topical treatments. Dips must cover the entire body. Spot treatments alone are not adequate.

Systemic therapy: oral itraconazole at 5 mg/kg every other day is the preferred systemic treatment for widespread or multi-cat infections. Terbinafine is an alternative. Griseofulvin is used less commonly now due to its side effect profile. Treatment duration is a minimum of 6 to 8 weeks and continues until two consecutive negative fungal cultures taken 2 to 4 weeks apart.

Environmental decontamination: vacuum daily (disposing of the vacuum bag after each session), wash bedding and soft furnishings frequently at high temperature, and wipe hard surfaces with diluted bleach (1:10). Diluted bleach kills ringworm spores effectively. HEPA vacuuming removes infected hairs from surfaces.

Ringworm control in multi-cat households is significantly more complex. All cats in the household must be tested and treated simultaneously, including cats that appear clinically normal. A single untreated carrier cat will reinfect treated cats.

Fungal culture of all in-contact cats, including those without lesions, is strongly recommended before starting treatment. This identifies carriers and ensures all sources of infection are addressed from the outset.

Dubai's warm and humid climate allows ringworm spores to survive longer on surfaces and in the environment compared to cooler climates. Rescue and shelter cats are at particularly high risk due to the stress of rehoming and shared living conditions, which can suppress immunity and promote spread.

If you have recently adopted a cat or are fostering, it is worth discussing a ringworm screen with your vet, particularly if the cat came from a multi-cat shelter environment. Early identification and treatment reduces the risk of infection spreading to people and other pets in your home.