Assessment of the performances of blood tests for the antemortem diagnosis of aspergillosis in wild or captive aquatic birds

The antemortem diagnosis of aspergillosis in birds remains a complex challenge. A variety of diagnostic methods are currently available, including direct detection of Aspergillus components, antibody-based assays, and nonspecific markers such as serum protein electrophoresis (SPE), but their diagnostic performances remain limited. The objective of this study was to assess and compare the performances of several diagnostic approaches, specifically, galactomannan index measurement, beta-D-glucan assay, 3-hydroxybutyrate quantification, SPE, and mannoprotein detection tests. A secondary objective was to develop a predictive model of aspergillosis incorporating optimal test thresholds identified in the first phase, combined with clinical signs. A total of 101 serum and 31 plasma samples were collected from 118 aquatic bird of various species in France. Birds were classified into three categories: control individuals (n = 88), suspected aspergillosis cases (n = 7), and confirmed cases (n = 23). While individually considered tests displayed limitations in specificity, predictive modeling revealed that elevated levels of 3-hydroxybutyrate above 0.52 mmol/L (Se = 96%, Sp = 51%) combined with beta-globulins above 6.90 g/L (Se = 78%, Sp = 51%), in conjunction with concurrent respiratory clinical signs, were significantly associated with the occurrence of aspergillosis. A multivariable logistic model combining these variables achieved excellent diagnostic performance, with AUCs up to 0.98 and sensitivity above 98%. These findings suggest that these parameters, particularly when considered alongside clinical signs, may serve as more reliable indicators for detecting aspergillosis in birds.