Toxoplasma gondii in Feline Populations: A Systematic Review of Hematological and Biochemical Markers with a One Health Perspective on Zoonotic Risk Assessment

Introduction: Toxoplasma gondii is an obligate intracellular zoonotic parasite, with felines as its definitive host, playing a pivotal role in transmission to humans and other animals. This systematic review aimed to investigate the associations between hematological and serum biochemical markers in cats infected with Toxoplasma and to assess their implications for public health.

Methods: A systematic search was conducted in accordance with PRISMA guidelines across PubMed, Scopus, Web of Science, and Google Scholar for studies published between January 2020 and December 2025. Inclusion criteria included observational, case-control, and cross-sectional studies that examined hematological and biochemical parameters in cats with specific anti-Toxoplasma antibodies (IgG and IgM). Data on complete blood count, biochemical profile, and inflammatory factors were extracted.

Results: Of the 1,324 studies identified, 38 met the inclusion criteria. The synthesized findings indicate that cats with acute Toxoplasma infection (IgM-positive) frequently presented with lymphopenia (reported in 65% of cases), mild neutrophilia (42%), and thrombocytopenia (38%). In the chronic phase, relative lymphocytosis and mild eosinophilia were the most commonly observed hematological changes. Biochemically, moderate elevations in liver enzymes (ALT and AST) were recorded in 47% of cases, and increased total protein (attributable to hyperglobulinemia) in 35% of cases. However, due to the inherent heterogeneity among the included observational studies, these pooled percentages should be interpreted with caution and are presented as descriptive summaries rather than definitive meta-analytical estimates.

Conclusion: From a One Health perspective, integration of routine hematological and biochemical markers with serological status may offer valuable supportive information for the clinical monitoring of feline toxoplasmosis. Nevertheless, the available evidence does not conclusively support the use of these nonspecific markers as a direct early warning system for predicting oocyst shedding, which primarily occurs during the acute phase of primary infection and is not directly determined by IgG titers or secondary hematological changes.