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Memórias do Instituto Oswaldo Cruz, Vol. 106, No. 6, Sept., 2011, pp. 781-782 Readers Opinion and Discussion Are all psittacine birds carriers of Cryptococcus neoformans? Guilherme Augusto Marietto-GonçalvesI, +; Fabrizio GrandiII, II ILaboratório
de Ornitopatologia, Departamento de Clínica Veterinária, Faculdade
de Medicina Veterinária e Zootecnia, Universidade Estadual Paulista,
Botucatu, SP, Brasil Received 26 May
2011 References
Reply In fact, the C. neoformans molecular type VNI strain collected from a commercial aviary in the city of Belém by Costa et al. (2009) was isolated from the excreta of caged budgerigars (M. undulatus). It is also important to note that Cryptococcus was not isolated in the "normal microbiota of psittacine birds maintened in captivity" but just from dried bird excreta (faeces plus urine) that had accumulated on the tray. Thus, the yeast was isolated from the external microenvironment of these bird cages. Actually, there is a mistake in supposing that the pathogenic species of Cryptococcus isolated by Abegg et al. (2006), Lugarini et al. (2008) and Santos et al. (2009) were present in the normal microbiota of healthy psittacine birds maintained in captivity. Their yeast isolations were done from the excreta of birds of the listed species kept in captivity. We did not affirm that the caged psittacinae were carriers of Cryptococcus, but merely noted the presence of this pathogenic yeast in their excreta exposed to external environmental conditions. It has been widely demonstrated that the contamination of such environments contributes to the aerial dispersion of propagules of C. neoformans, thus allowing their transmission to humans and other mammals. Moreover, it is important to note that cryptococcosis is not a zoonotic infection and that humans and other animals may be contaminated, colonised or infected, depending on their susceptibility. The occurrence of C. neoformans in bird excreta is essentially a saprobiotic phenomenon, without any specificity for a particular bird species. Therefore, the isolation of C. neoformans from the excreta of a particular bird species does not necessarily mean that this vertebrate is a host or a carrier of the yeast. Sites shielded from direct sunlight and ultraviolet light in which substrata rich in urea and other nitrogenous sources accumulate, high avian density and poor hygiene are likely to become contaminated microenvironment by Cryptococcus. Pigeon habitats in urban environments are the most studied sources of Cryptococcus throughout the world (Mitchell et al. 2011). Crop colonisation and mechanical transport through external contamination of pigeon feathers and feet by C. neoformans has been reported, but more studies are necessary to determine importance of pigeons in the transmission of these yeasts to humans and other mammals. In addition, the droppings of caged birds [such as Paroaria dominicana (red-cowled cardinal), Serinus canarius, Serinus flaviventris (yellow canary), Sicalis flaveola (saffron finch), Sporophila caerulescens (double-collared seedeater)] kept in domestic environments in Rio de Janeiro showed 12.7% positivity (10/79) for C. neoformans (Passoni et al. 1998). Besides the domestic environments, commercial stores that sell birds are prone to harbour C. neoformans due the high frequency of the conditions described above. For instance, in the city of Campo Grande, Mato Grosso do Sul, a study of bird droppings identified C. neoformans serotype A in cages of budgerigars in a commercial store (Filiú et al. 2002). The original and natural budgerigar habitats are not necessarily positive for C. neoformans. Pigeon excreta are the most common known environmental reservoir of C. neoformans VNI and the excreta of captive budgerigars are also a potential source for this molecular type depending on local micro-environmental factors, especially available nutrient sources and physical conditions. Finally, we emphasise that the isolation of C. neoformans from bird excreta collected in the environment in which they live, in nature or in captivity, does not mean that a particular bird species has as specific role as a reservoir or that this fungus is part of the natural microbiota of these vertebrates. Furthermore, there is no scientific evidence that the fungus has the ability to grow or survive in the excreta of a specific bird. References
Bodo
Wanke Solange
do Perpétuo Socorro Evangelista Costa Copyright © 2011 - Instituto Oswaldo Cruz - Fiocruz |
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