What is the source of ringworm infection?

Sources of Ringworm Infection

Ringworm (dermatophytosis) is primarily acquired through direct contact with infected humans, animals, or contaminated objects and environments, with animals being a particularly common source of infection. 1

Animal Sources of Ringworm

Ringworm can be transmitted from various animal sources:

• Pets:

  • Cats are among the most common sources, particularly for Microsporum canis infections 2, 3
  • Dogs can carry multiple species of dermatophytes 3
  • Rodents (guinea pigs, hamsters) often carry Trichophyton mentagrophytes var. benhamiae 3
  • Hedgehogs typically carry Trichophyton mentagrophytes var. erinacei 3

• Livestock:

  • Cattle commonly carry Trichophyton verrucosum 3
  • Sheep and goats can transmit ringworm, particularly during agricultural shows 1
  • Rabbits frequently carry Trichophyton mentagrophytes complex 3

• Wildlife and exotic animals:

  • Zoo animals have been documented sources of outbreaks 1
  • In one case, a hand-reared zoo tiger cub was the source of ringworm infection in 23 people 1

Human-to-Human Transmission

• Direct contact with infected individuals 4, 5
• Barber shops and hair salons can be transmission sites through contaminated tools 4
• Shared facilities such as locker rooms, swimming pools, and communal showers 5
• Household transmission between family members 5

Environmental Sources

• Contaminated objects (fomites):

  • Combs, brushes, hats, clothing, and towels 5
  • Bedding and furniture 5
  • Hairdressing tools and equipment 4

• Soil can harbor geophilic dermatophytes like Nannizia gypsea 3

Risk Factors for Acquisition

• Age: Children are more susceptible, particularly to tinea capitis 3
• Close contact settings: Schools, daycare centers, sports facilities 5
• Animal exhibitions: County fairs, petting zoos, educational farms 1
• Occupational exposure: Veterinarians, animal handlers, farmers 2
• Immunocompromised status: Increases susceptibility to infection 5

Prevention Strategies

• Hand hygiene: Thorough handwashing after animal contact is the single most important preventive measure 1
• Animal management: Regular veterinary care and proper husbandry for pets and livestock 1
• Environmental cleaning: Disinfection of shared equipment and surfaces 4
• Public education: Information about disease risks and prevention in settings with animal contact 1

Clinical Considerations

• Ringworm infections typically present as circular, scaly patches with central clearing 6
• Diagnosis is confirmed through microscopic examination with KOH preparation and fungal culture 2
• Treatment typically involves topical antifungals for localized infections and oral antifungals for extensive or hair/nail involvement 7

Special Situations

• In public settings with animals, transition areas between animal and non-animal areas are recommended to reduce transmission risk 1
• During outbreaks linked to animals, extensive public health investigation may be necessary to identify all exposed individuals 1
• Younger animals with long hair are more likely to be carriers of dermatophytes 3

Understanding the sources of ringworm infection is crucial for implementing effective prevention strategies and promptly identifying potential outbreaks, particularly in settings where humans and animals interact.