Ringworm or tinea (dermatophytosis)

Ringworm or tinea (dermatophytosis) includes tinea capitis (head), tinea corporis (body), tinea pedis (feet), tinea cruris (groin) and tinea unguium (nails).

Notification requirement for ringworm or tinea

Notification is not required.

Primary school and children’s services centres exclusion for ringworm or tinea

Exclude until the day after appropriate treatment has commenced.

Infectious agent of ringworm or tinea

Microsporum spp. include Microsporum canis as the primary causative agent in Australia of tinea capitis and tinea corporis. Trichophyton spp. – for example, T. rubrum and T. mentagrophytes – and Epidermophyton floccosum also cause disease.

Identification of ringworm or tinea

Clinical features

The clinical features of tinea infections are those of superficial fungal infection of the skin, nails or hair:

• Tinea capitis results in a small papule that spreads peripherally, leaving fine, scaly patches of temporary baldness. Infected hairs become brittle and break off easily. A large abscess known as a kerion can form as a result of vigorous immune response, and may be misdiagnosed as bacterial infection.
• Tinea corporis appears as a flat, erythematous, ring-shaped lesion of the skin (‘ring worm’). It is usually dry and scaly, or moist and crusted, but sometimes contains fluid or pus. The lesion tends to heal centrally.
• Tinea pedis occurs as itchy, scaling, cracked skin, or blisters containing a thin watery fluid. This occurs commonly between the toes (‘athlete’s foot’).
• Tinea cruris is fungal infection of the groin, perineum and buttocks (‘jock itch’). Confluent, erythematous plaques with a leading edge occur, often following spread from feet.
• Tinea unguium is a chronic fungal disease involving one or more nails of the hands or feet (onychomycosis). The nail gradually thickens and becomes discoloured and brittle. Caseous material forms beneath the nail, or the nail becomes chalky and disintegrates.

Diagnosis

Diagnosis can be made by microscopic examination of material from the affected area or by fungal culture.

Incubation period for ringworm or tinea

The incubation period differs:

• Tinea corporis has an incubation period of 4-10 days.
• Tinea capitis has an incubation period of 10-14 days.
• The incubation period of tinea pedis and tinea unguium is probably weeks, but exact limits are unknown.

Public health significance and occurrence of ringworm or tinea

Tinea capitis mainly affects children.

M. canis is usually contracted from infected kittens or puppies.

The highly contagious M. audouinii spreads from person to person and does not occur in Australia.

Tinea capitis may extend to tinea corporis. It occurs worldwide.

Tinea corporis occurs worldwide and is relatively prevalent. Males are infected more than females. Infection can occur from direct or indirect contact with skin and scalp lesions of infected people or animals.

Tinea pedis occurs in children and adults. It is spread via shed skin scales, which may remain infectious on carpet or matting for years. Adults are affected more often than children, and males more often than females. Infection is more frequent and severe in hot weather.

Tinea cruris is commonly spread from the affected individual’s feet, and hence causative agents and occurrence are similar to tinea pedis. Young men are most frequently affected.

Tinea unguium occurs commonly, but rates of transmission are low, even to close family associates. It is spread by direct contact with skin or nail lesions of infected people, or indirectly through contact with contaminated floors or showers.

Reservoir for ringworm or tinea

Reservoirs for tinea are:

• tinea capitis – humans and animals, including dogs, cats and cattle
• tinea corporis – humans, soil and animals, including cattle, kittens, puppies, guinea pigs, mice and horses
• tinea pedis/cruris – humans
• tinea unguium – humans and, rarely, animals or soil.

Mode of transmission of ringworm or tinea

Direct transmission occurs through human-to-human contact – for example, for T. rubrum and T. mentagrophytes. Animal-to-human contact also occurs – for example, for M. canis and T. verrucosum. Tinea can also be transmitted indirectly through contaminated soil – for example, for M. gypseum.

Period of communicability of ringworm or tinea

Active lesions shed infective material continuously. The fungus persists on contaminated materials for as long as skin cells or animal hair harbour viable spores.

Susceptibility and resistance to ringworm or tinea

Young children are particularly susceptible to tinea capitis (M. canis). All ages are susceptible to infections, particularly those caused by Trichophyton spp.

Susceptibility to tinea corporis is widespread. It is aggravated by friction and excessive perspiration in axillary and inguinal regions, and when environmental temperatures and humidity are high.

Susceptibility is variable for tinea pedis, and infection may be inapparent. Repeated attacks are frequent.

An injury to the nail predisposes to tinea unguium infection. Reinfection is frequent.

Control measures for ringworm or tinea

Preventive measures

Measures differ according to cause:

• For tinea capitis, parents should be educated about modes of spread from infected children and animals.
• For tinea corporis, shower bases, shower mats and floors adjacent to showers should be disinfected. Infected animals should be avoided.
• For tinea pedis, gymnasiums, showers and similar sources of infection should be thoroughly cleaned and washed. Shower areas should be frequently hosed and rapidly drained. Users of such areas should be encouraged to carefully dry (and perhaps powder) between their toes.

Control of case

In general, cases should be advised not to share towels or clothing with others. Specific control depends on the cause:

• For tinea corporis, infected children should be excluded from schools and swimming pools until at least the day following the commencement of appropriate treatment. It can be treated effectively with topical medications.
• For tinea capitis, oral griseofulvin is the treatment of choice for resistant infection – for example, T. tonsurans. Topical antifungal medication may be used concurrently.
• For tinea cruris, treat as for tinea corporis; however, also ensure that any concurrent tinea pedis is treated to prevent reinfection.
• For tinea pedis, topical fungicides are recommended, but oral griseofulvin may be indicated in severe, protracted disease. Feet should be kept as dry as possible and exposed to air by wearing sandals. Socks of heavily infected individuals should be boiled or discarded to prevent reinfection.
• For tinea unguium, oral terbinafine should be given daily for 6–12 weeks for fingernails and 3–6 months for toenails.

Consult the current version of Therapeutic guidelines: antibiotic for detailed guidance on therapy.

Note: M. canis infection is self-limiting in children before puberty, and griseofulvin may not be necessary. Consult a specialist about treatment.

Control of contacts

Investigate household contacts, pets and farm animals for evidence of infection. Treat infected contacts (human or animal).

Control of environment

See ‘Preventive measures’.

Outbreak measures for ringworm or tinea

Children and parents should be educated about modes of spread, prevention and the necessity of maintaining a high standard of personal hygiene. In case of outbreaks, consider examination of all children to identify cases. Disinfect contaminated articles.