IN HUMANS continued
factors for dermatophyte infection include underlying diseases such as diabetes mellitus, immunosuppressant medications, neoplasia and anaemia. In immunocompromised individuals the most common complication of M. canis infection is a protracted treatment time. 5,17 • Human diagnosis traditionally relies on skin scrapings for detection of dermatophytes and fungal culture for confirmation and species differentiation. Culture for dermatophytes requires up to 4 weeks. Increasingly, multiplex dermatophyte PCRs are being introduced routinely, as these can confirm and differentiate dermatophyte species within 24 hours of testing, thus aiding clinical management.
• Microsporum canis is considered one of the most common causes of tinea capitis in children and can be divided clinically into inflammatory and non-inflammatory types. 14,15 The non- inflammatory type is characterised by areas of patchy circular alopecia, stubbled hair and mild scaling. The inflammatory type has lesions with diffuse, patchy alopecia, erythema, crusting scale, kerion formation and pustules. It may be associated with painful regional lymphadenopathy. 16 Tinea capitis occurs mainly in children between 3 and 14 years of age but can affect any age group. 17 It may also involve the eyelashes and eyebrows. 17 • Immunocompromise can lead to impaired hair shaft strength and growth allowing dermatophyte colonisation. Predisposing
KEY CONSIDERATIONS 1. Approximately 50% of humans exposed to M. canis infected cats acquire the infection, and in 30-70% of households with an infected cat, at least one cohabitating human will become infected. 2. Diagnosis in animals is based on a combination of clinical suspicion, the results of Wood’s lamp and microscopic examination and/or fungal culture. 3. As shed arthrospores can remain infective for 12 to 24 months, contaminated fomites (such as bedding, collars, brushes and toys) may be a source of infection or ongoing re-infection. Thorough cleaning and disinfection is needed to minimise the risk.
Following diagnosis in a pet, all in-contact animals and
household members should be screened for dermatophytes using fungal culture. Individuals and animals testing positive should be treated irrespective of whether they are symptomatic.
References: 1. Wisal, G.A., (2018) An overview of canine dermatophytosis. South Asian J Res Microbiol , 2, 1-16. 2. Smith, M.B., et al (2006), Dermatophytosis. In: Tropical Infectious Diseases . Elsevier. 884-891. 3. Paryuni, A.D., et al (2020) Dermatophytosis in companion animals: A review. Vet World, 13(6), 1174. 4. European Scientific Counsel Companion Animal Parasites (2019) Guideline 2, Fourth Edition. Superficial mycoses in dogs and cats. 5. Moriello, K.A., et al (2017) Diagnosis and treatment of dermatophytosis in dogs and cats. Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Vet Dermatol, 28(3), 266-e68. 6. Cafarchia, C., et al (2006) Isolation of Microsporum canis from the hair coat of pet dogs and cats belonging to owners diagnosed with M. canis tinea corporis. Vet Dermatol, 17(5), 327-331. 7. Hnilica, K.A., et al (2017), Fungal Skin Diseases. In: Small Animal Dermatology-E-Book: A Color Atlas and Therapeutic Guide , 4th. W.B Saunders. 8. Frymus, T., et al (2013) Dermatophytosis in cats: ABCD guidelines on prevention and management. J Feline Med Surg , 15(7), 598-604. 9. Sparkes, A., et al (1994) Microsporum canis : inapparent carriage by cats and the viability of arthrospores. J Small Anim Pract, 35(8), 397-401.
10. Mancianti, F., et al (2003) Environmental detection of Microsporum canis arthrospores in the households of infected cats and dogs. J Feline Med Surg , 5(6), 323-8. 11. McPherson, M.E., et al (2008) High prevalence of tinea capitis in newly arrived migrants at an English-language school, Melbourne, 2005. Med J Aust , 189(1), 13-16. 12. McPhee, A., et al (2016) How much human ringworm is Zoophilic? Sullivan Nicolaides Pathology , accessed 4 Apr 2021 . 13. Leung, A.K., et al (2020) Tinea corporis: an updated review. Drugs Context , 9. 14. Scott, D.W., et al (1987) Zoonotic dermatoses of dogs and cats. Vet Clin North Am Small Anim Pract , 17(1), 117-144. 15. Pasquetti, M., et al (2017) Infection by Microsporum canis in paediatric patients: a veterinary perspective. Vet Sci , 4(3), 46. 16. Fuller, L., et al (2014) British Association of Dermatologists’ guidelines for the management of tinea capitis 2014. Br J Dermatol , 171(3), 454-463. 17. Al Aboud, A.M., et al (2020) Tinea capitis. StatPearls [Internet].
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