Abstract
Feline panleukopenia (FPL) is a serious viral disease caused by Feline panleukopenia virus (FPV) that causes leukopenia, lymphopenia, and neutropenia, particularly in young or unvaccinated cats. There is no specific antiviral treatment available for FPL, and treatment protocols generally consist of fluid therapy and supportive care. This study evaluated the clinical and hematological efficacy of filgrastim, a granulocyte colony-stimulating factor (G-CSF) that has shown successful results in treating FPL in various studies, and the paraimmune activator-inactivated Parapoxvirus ovis (iPPVO) in 49 cats naturally infected with FPV. Cats were randomly assigned to four groups: low-dose filgrastim (5 µg/kg, n = 13), high-dose filgrastim (20 µg/kg, n = 14), iPPVO (n = 12), and standard supportive treatment (n = 10). Clinical signs and complete blood counts were assessed on days 0 and 7. By day 7, high-dose filgrastim showed greater increases in white blood cell, lymphocyte, monocyte, and neutrophil counts compared with the other groups (p < 0.05), whereas moderate improvements were observed in the iPPVO group. Leukopenia and lymphopenia resolved faster in the high-dose filgrastim group than in the low-dose filgrastim and standard treatment groups. Clinical recovery, including reduction in vomiting and lethargy, was more pronounced in the high-dose filgrastim and iPPVO groups. Survival rates did not differ significantly among groups (p = 0.615), although the high-dose filgrastim group showed the lowest mortality (42.9%). These findings suggest that high-dose filgrastim may contribute to cytopenias and promote hematological recovery in FPL, while iPPVO may serve as a supportive immunomodulatory therapy. However, it should be noted that the efficacy of filgrastim and/or iPPVO treatments has not been definitively confirmed, likely due to the small sample size and the lack of well-controlled randomized studies.