zoonoses and communicable diseases common to ... - PAHO/WHO

332 MYCOSESDERMATOPHYTOSISICD-10 B35Synonyms: Tinea, dermatomycosis, ringworm.Etiology: Several species of Microsporum and Trichophyton and the speciesEpidermophyton floccosum. Ecologically and epidemiologically, three groups ofspecies are distinguished according to the reservoir: anthropophilic, zoophilic, andgeophilic. This discussion will consider only zoophilic species transmissible to man.Dermatophytes were formerly considered imperfect fungi, Fungi imperfecti orDeuteromycotyna. However, several species have been shown to reproduce sexually.The most important zoophilic species are Microsporum canis (whose perfect statereceived the name Nannizzia otae), Trichophyton mentagrophytes (Arthrodermabenhamiae), and T. verrucosum. Species of more limited interest are M. equinum, T.equinum, M. gallinae, M. nanum, M. persicolor, and T. simii. The species T. mentagrophytesis subdivided into two varieties: T. mentagrophytes var. erinacei and var.quinckeanum.The infecting element is the arthrospore (an asexual spore formed in the hyphaeand released when these break down) of the parasitic phases. Conidia that form inorganic material substrates (where the fungus may form sexual and asexual spores)may also be infective.A notable characteristic is that the hyphae and spores are highly resistant indesquamated epithelium, where they may remain viable for several months or evenyears if they don’t dry up.Geographic Distribution: Among the zoophilic species, M. canis, T. verrucosum,T. equinum, and T. mentagrophytes are distributed worldwide. T. mentagrophytesvar. erinacei has limited distribution (France, Great Britain, Italy, and NewZealand) and T. simii is limited to Asia. The geographic distribution of these fungidepends on the dispersion of the host animals. The host hedgehog of T. mentagrophytesvar. erinacei exists only in Europe and in New Zealand, where it was introducedfrom Europe. The abundance or rarity of a dermatophyte species dependslargely on the rural or urban habitat and the relationship between man and animals.M. canis is a fungus that occurs primarily in urban areas where its natural hosts, thedog and cat, are abundant and in close contact with humans. In contrast, T. verrucosumis found in rural areas, particularly among stabled cattle, i.e., generally in areaswith cold or temperate climates.Occurrence in Man: Dermatophytic infections are common, but their exact prevalenceis unknown. The disease is not notifiable and, moreover, many people withminor infections do not see a doctor. Most of the data come from dermatologists,mycology laboratories, and epidemiologic investigations. Economically advancedcountries have experienced a marked reduction in some species of anthropophilic dermatophytes.This is true of M. audouinii, which causes epidemic outbreaks of tineacapitis. In such countries, zoophilic dermatophytes are now much more significant. Astudy conducted in England on 23 families to evaluate the prevalence of the infectionamong family members who were in contact with clinically or sub-clinically infectedyoung cats found that 46 (50%) out of 92 individuals contracted the infection due to