Seroprevalence and risk factors associated with Brucella seropositivity in dairy and mixed cattle herds from Ecuador.

An extensive cross-sectional study to determine the seroprevalence of and associated risk factors for Brucella infection was performed in dairy and mixed (dairy-beef) cattle herds in Ecuador. A total of 2666 serum samples from 386 farms were analyzed using Rose Bengal test and a blocking ELISA test. In addition, a questionnaire with 57 variables related to management, feeding, facilities, biosecurity, and animal health was filled in every cattle farm. A Generalized Estimating Equations model was used to determine the factors associated with Brucella seropositivity. The true prevalence of Brucella seropositivity in dairy and mixed cattle from Ecuador reached 17.0% (CI95% 15.6-18.4%). The herd prevalence was 45.1% (174/386) (CI95% 40.1-50.1%), and the within-herd prevalence ranged from 10 to 100% (mean 38.9%; Q1 14.3%, Q2 26.8%, Q3 52.5%). Seven factors were included in the GEE model for Brucella seropositivity: the nominal variables sex (OR 2.03; CI95% 1.32-3.13), herd type (dairy) (OR 1.79; CI95% 1.11-2.87), closed facilities in the farm (OR 1.80; CI95% 1.19-2.74), and ad libitum feeding (OR: 0.32; CI95%: 0.19-0.54), and the quantitative variables age (OR 1.005; CI95% 1.001-1.009), average slope in the farm (%) (OR 1.013; CI95% 1.002-1.024), and annual abortion rate (OR 1.016; CI95% 1.002-1.031). This study remarks the high spread of Brucella infection in cattle farms from Ecuador. In addition, it reports the risk factors associated to this infection in the predominant extensive system existent in this country.

Detection of platelet-associated immunoglobulins by flow cytometry for the diagnosis of immune thrombocytopenia: a prospective study and critical review.

BACKGROUND AND OBJECTIVE: Flow cytometry (FC) to identify platelet-associated (PA) immunoglobulin (Ig) is a potentially useful diagnostic test for idiopathic thrombocytopenic purpura (ITP). However, the restricted application of PAIg measurement to thrombocytopenic populations primarily comprised of ITP patients will artificially enhance the test's diagnostic specificity. For this reason, we performed a prospective study in which the results of a sensitive technique for detecting PAIg, as is FC, were correlated to the cause of the thrombocytopenia. DESIGN AND METHODS: A total of 118 patients with platelet counts <100 x 10(9)/L and 30 normal donors with a platelet count >200 x 10(9)/L were studied for PAIg employing a flow cytometer. Forty-two children and 20 adults were diagnosed as having immune thrombocytopenia and 27 children and 29 adults had nonimmune thrombocytopenia of different etiology. RESULTS: Raised levels of PAIg were found in 56/62 patients with immune thrombocytopenia and in 34/56 patients with non-immune thrombocytopenia. Diagnostic values of PAIg for the detection of immune thrombocytopenia were: sensitivity 90.3% and specificity 39. 3%. An enzyme-linked immunoabsorbant assay (ELISA) for the detection of autoantibodies to platelet glycoprotein (GP) complexes was used in adults, 9 with immune-related thrombocytopenia and 16 with non-immune thrombocytopenia, in order to determine the true non-specific nature of the positive PAIg test. By ELISA, 8/9 patients with immune thrombocytopenia and 7/16 with non-immune thrombocytopenic disorders showed autoantibodies to platelet GP complexes. INTERPRETATION AND CONCLUSIONS: PAIg detection by FC constitutes a sensitive but non-specific assay thus making it unnecessary and inappropriate for establishing the diagnosis of ITP.