Hematological and biochemical profiles, infection and habitat quality in an urban rat population

Host condition is key in understanding disease dynamics. In this study, we investigated the relationship between infection with Leptospira interrogans and helminths, and the hematological and hormone-biochemical stress-related profiles of urban Rattus norvegicus. Rat kidney imprints and urine were used to identify and quantify L. interrogans, while fecal samples were analyzed for helminth eggs and corticosterone metabolites. Blood samples were taken for complete blood counts and specific biochemicals in rats' sera. Principal Component Analyses were conducted to group rats according to health profiles. A total of 120 rats were captured, and hematological and hormone-biochemical data were obtained from 95 and 61 rats, respectively. Hematological PCA revealed distinct rat groups: typical (T), eosinophil-deficient (Eos-D), eosinophil- and monocyte-deficient (EM-D) and monocyte deficient with high immature neutrophils (Mon-D). No significant association was found between L. interrogans or helminth infections and health profiles, except for Trichiuridae helminths, which had significantly higher mean intensity in the pooled deficient groups compared to the T-group. The poorest condition group was found in areas with fewer rat burrows than the T-group, indicating EM-D had a reduced ability to occupy higher-quality habitats. These findings suggest that hematological profiles may reflect host's overall condition, instead of responses to specific infections.