Diagnóstico histopatológico e imuno-histoquímico de micoses e oomicoses em animais domésticos

Abstract

This thesis was composed of three scientific papers. The first paper was the more comprehensive one. All necropsy and biopsy cases of mycoses and oomycosis diagnosed in domestic animals between 1990 and 2012 were analyzed. In the studied period, 29,686 exams (9,487 necropsy reports and 20,199 biopsy reports) performed at the Laboratório de Patologia Veterinária (LPV) of the Universidade Federal de Santa Maria (UFSM) were studied. Two hundred and thirty cases of mycosis or pythiosis (oomycosis) were found, being 179 cases (78%) of mycoses and 51 cases (22%) of pythiosis. The main diseases observed, in descending order of prevalence, were: pythiosis, candidiasis, aspergillosis, zygomycosis, dermatophytosis, mallasseziosis, cryptococcosis, megabacteriosis, and sporothrichosis. Pythiosis affected mainly horses and the mycosis affected mainly dogs and cats. The second article focused on the histomorphological and histochemical characteristics determinant for the histopathological diagnosis of this condition in dogs and cats. By the hematoxylin-eosin (HE) stain, the yeasts were round, with a central cell containing a nucleus, surrounded by a clear halo (usually non-stained capsule). The techniques of periodic Schiff acid (PAS), Grocott, and Fontana-Masson (FM) were utilized and demonstrated the wall of the yeast cells. The FM stain showed the melanin present in these cells. The Alcian blue and Mayer s mucicarmin stains showed mainly the yeast polysaccharide capsule. The diameter of the cells ranged from 1.67 to 10.00μm and the full diameter of the encapsulated yeasts varied between 4.17 e 34.16μm. Yeast buddings were better observed through the PAS stain and were narrow based, simple or multiple, mainly in the opposite poles of the cells, or forming chains. The third article emphasized an immunohistochemical (IHC) study of cases of aspergillosis and zygomycosis aiming to optimize the use of the IHC technique in the detection of Aspergillus spp. and zygomycetes in animal tissues. Two fungal-specific monoclonal antibodies were utilized in tissue fragments (formalin-fixed paraffin-embedded) previously diagnosed as aspergillosis or zygomycosis. Tissues were submitted to three different detection systems (two biotinilated and one nonbiotinilated). Both antibodies showed high specificity and sensitivity in the examined tissues. No cross-reactions were observed between the antibodies utilized and the agents evaluated (including cases of aspergillosis, zygomycosis, candidiasis, and pythiosis). However, nonspecific reactions were observed in hyphae of some cases, but were eliminated by mean of one of the detection systems used. The IHC technique showed to be a useful tool detecting and confirming aspergillosis and zygomycosis in this retrospective study.