RESUMO
The current method for goat brucellosis diagnosis is based on the World Organization for Animal Health (OIE) using the screening card test (CT), with antigen at 8% (CT8) or 3% (CT3) of cell concentrations, and the confirmatory complement fixation test (CFT). However, these tests do not differentiate antibodies induced by vaccination from those derived from field infections by Brucella species or other bacterial agents; in places like Mexico, where the prevalence of brucellosis and the vaccination rates are high, there is a considerable percentage of false positive reactions that causes significant unnecessary slaughter of animals. Furthermore, results of the fluorescence polarization assay (FPA) using the Brucella abortus O-polysaccharide (OPS) tracer in goats are poorer than those with cattle. The present study was undertaken to investigate a tracer prepared from the native hapten (NH) of the Rev. 1 strain of Brucella melitensis to improve FPA performance on goat brucellosis diagnosis. Evaluation of 48 positive samples and 96 negative samples showed that the NH tracer was more accurate (p<0.01) than the OPS tracer (97.2% vs. 93.8% accuracy, respectively). On the diagnostic performance evaluation, the NH tracer performed better (87.5% accuracy, 79.5% sensitivity, 84.3% specificity, and 163.8 performance index) than the OPS tracer (83.5%, 75.9%, 81.0%, and 156.9, respectively) using 1009 positive and 2039 negative Mexican field goat sera samples selected by test series approved by the OIE (card test 3% and CFT). We demonstrated a new application for the NH lipopolysaccharide on detecting antibodies against Brucella using the FPA, which may yield faster results (minutes vs. 24-72h) than the immunodiagnosis assays frequently used in bovine brucellosis. In addition, NH tracer produces similar or better performance results than the conventional OPS tracer, using the FPA in goat sera samples.
Assuntos
Anticorpos Antibacterianos/sangue , Brucella melitensis/imunologia , Brucelose/veterinária , Imunoensaio de Fluorescência por Polarização/veterinária , Doenças das Cabras/microbiologia , Haptenos/química , Animais , Anticorpos Antibacterianos/imunologia , Brucella abortus/imunologia , Brucella melitensis/química , Brucelose/diagnóstico , Brucelose/imunologia , Brucelose/microbiologia , Bovinos , Fluoresceína-5-Isotiocianato/química , Imunoensaio de Fluorescência por Polarização/métodos , Corantes Fluorescentes/química , Doenças das Cabras/sangue , Doenças das Cabras/diagnóstico , Doenças das Cabras/imunologia , Cabras , Haptenos/imunologia , Curva ROC , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Bacteriological investigation of canine brucellosis in Mexico City revealed a high rate (11.8%) of Brucella canis infection in a sampling of 59 stray dogs. When conservative criteria were employed in the interpretation of serological test results, there was general agreement between the serological and bacteriological findings; however, some animals with localized male genital tract infections could not be judged as infected solely by serological tests. All Mexican field isolates were identified as B. canis; however, some diversity was observed as regards nitrate reduction, growth in the presence of basic fuchsine, and the degree of mucoidness. The seemingly high prevalence of B. canis infection in Mexico City dogs suggests the need for further inquiry into the possible public health significance.