Estudo anatomopatológico e imunoistoquímico da pitiose em eqüinos naturalmente infectados Anatomopathological and immunohistochemical study of pythiosis in naturally infected horses

O trabalho teve como objetivo comparar a técnica de Grocott metanamina de prata (GMS) com o método imunoistoquímico de streptavidina-biotina marcada (LSAB) no diagnóstico da pitiose. Fragmentos de feridas cutâneas suspeitas de pitiose provenientes de 55 eqüinos foram processados pelas técnicas de hematoxilina/eosina, GMS e imunoperoxidase (LSAB). Trinta e quatro casos foram positivos pelo GMS, dos quais 28 apresentaram imunomarcação (LSAB) positiva para Pythium insidiosum. Os seis casos restantes apresentaram diagnóstico compatível de zigomicose. Foram diagnosticados como tecido de granulação com infiltração de eosinófilos sem áreas de necrose (nove casos), tecido de granulação com infiltrado de eosinófilos e presença de áreas de necrose (sete), habronemose (quatro) e sarcóide (um). Concluiu-se que a imunoperoxidase pelo método LSAB apresenta maior especificidade no diagnóstico de infecção pelo P. insidiosum do que pelo método GMS.<br>The main goals of this study were to perform an anatomopathological evaluation of equine tissue naturally infected with Pythium insidiosus and to compare the reliability of Grocott methenamine silver nitrate (GMS) and the labeled streptavidin-biotin (LSAB) techniques for the diagnosis of pythiosis. Samples of cutaneous wounds suggestive of pythiosis obtained from 55 horses were histologically studied using hematoxylin-eosin and GMS stains, and LSAB. Twenty eight, out of 34 GMS-positive samples, were LSAB-positive for Pythiuminsidiosum. The six LSAB-negative samples were apparently cases of zygomicosis. The remaining samples were diagnosed as follow: granulation tissue with eosinophilic infiltration without necrotic areas (nine cases); granulation tissue with eosinophilic infiltration and necrotic areas (seven); habronemiasis (four); sarcoid (one). In conclusion, the LSAB method was more specific for the diagnosis of P. insidiosum when compared to GMS