Filgrastim Efficiency in Cats Naturally Infected with Feline Panleukopenia Virus

Feline Panleukopenia (FPL) infection is caused by feline panleukopenia virus (FPV), and it is considered one of the most severe cat's infectious diseases. Since there is no specific antiviral treatment for FPL, the therapeutic protocol usually is focused on fluid therapy and supportive care. However, filgrastim, a granulocyte colony-stimulating factor (G-CSF) used in human medicine to treat neutropenia and leukopenia, has been lately used in treating FPV disease, providing promising results. During January 2022 and September 2024, twenty-two cats diagnosed with feline panleukopenia virus were subjected to filgrastim (Zarzio^®, Sandoz, Kundl, Austria) administration at a dose of 6 µg/kg for 3 consecutive days. The 4th day was a break day, and in the 5th day, the complete blood count was repeated. White blood cells, lymphocytes, monocytes, neutrophils and eosinophils parameters improved after Zarzio^® administration, with a significant statistical difference (<i>p</i> < 0.01) when their values between day 1 (pre Zarzio^® administration) and day 5 (post Zarzio^® administration) were analysed. However, red blood cells, haemoglobin, haematocrit and platelets parameters registered a considerable reduction from day 1 to day 5 with a significant statistical difference (<i>p</i> < 0.01), considered as post-administration side effects. In our study, the survival rate following Zarzio^® administration was 100%, suggesting that the protocol involving three doses is effective in restoring the leukopenia and neutropenia.