Assessment of Metabolites in Sera and Cerebrospinal Fluids of Rabies-Infected Dogs (Nigeria)

Introduction : Rabies remains a neglected zoonotic disease of global public health importance due to its near-universal fatality, lack of reliable preclinical diagnostics, and absence of effective treatment after symptom onset. Methodology : This study investigated early metabolic alterations associated with rabies virus infection by profiling serum and cerebrospinal fluid (CSF) metabolites in naturally infected dogs during the incubation phase. A total of 231 samples (brain tissue, serum, and CSF) were obtained from dogs slaughtered for human consumption in southeastern and north-central Nigeria. Results : Rabies antigen was detected in brain tissues using the direct fluorescent antibody test, identifying 20 positive cases (8.7%). Corresponding serum and CSF samples were classified as rabies-positive, while 20 negative samples were selected for comparison. Untargeted metabolomic analysis was performed using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS). Data processing included contaminant removal, normalization, batch correction, and scaling, followed by multivariate, univariate, pathway enrichment, and ROC analyses. The serum dataset yielded 868 retained compounds, while 300 compounds were retained from CSF after quality control. Missing data did not differ significantly between groups. Pathway analysis revealed significant perturbations in glycerolipid metabolism, glyoxylate and dicarboxylate metabolism, the pentose phosphate pathway, and amino acid metabolism in serum. Four serum metabolites remained significant after correction, with an unannotated compound (Analyte 634) showing strong discriminatory ability (AUC = 0.962). CSF analysis indicated enrichment in pentose phosphate, glutathione, and nicotinate metabolism. Indolelactic acid was consistently downregulated in both matrices. One shared metabolite was detected in serum and CSF. Conclusion : Overall, the findings demonstrate early metabolic disturbances during rabies infection and identify potential biomarkers for preclinical detection