Evaluation of Immune Response Dynamics: Analyzing the Parameters of Complete Blood Count (CBC) in Experimental Borreliosis

The spirochete <i>Borrelia</i> is responsible for Lyme disease, a multisystemic infection and growing public health concern. This study aimed to evaluate host response dynamics to <i>Borrelia bavariensis</i> by analyzing hematological parameters as potential immuno-inflammatory markers in a murine model. Forty C3He/HeNCrl mice were inoculated intradermally with <i>B. bavariensis</i> (5 × 10⁵ spirochetes/100 µL/mouse) and monitored for 90 days. Samples were collected at defined intervals for microbiological examination, hematology, and qPCR. Microbiological and qPCR testing revealed infection between days 7-21; results were negative on days 28-42. At later stages (days 60 and 90), <i>Borrelia</i> was only detectable by qPCR, highlighting differences in diagnostic sensitivity. Hematological analysis showed that the neutrophil-to-lymphocyte ratio (NLR) and systemic immuno-inflammatory index (SII) peaked on day 7 (<i>p</i> < 0.0001), followed by gradual normalization until day 35. These markers reflected the intensity of the inflammatory response and defined three distinct phases of host reaction. Overall, results demonstrate the complexity of immune responses in <i>B. bavariensis</i> infection and underscore the value of monitoring hematological indices for understanding host-pathogen interactions. This approach supports the potential use of simple blood markers in diagnostic strategies with translational relevance for clinical practice.