Feline panleukopenia (cat parvovirus) is a devastating and often fatal disease. Vaccination is highly effective and is the primary welfare protection for unvaccinated cats.
Feline panleukopenia causes extreme suffering through severe bloody diarrhea, vomiting, profound immune suppression and rapid deterioration. Kittens with panleukopenia require intensive hospitalization with IV fluids, antibiotics and supportive care for any chance of survival. Vaccination prevents this entirely. The welfare cost of panleukopenia in unvaccinated populations is enormous and the vaccine is among the safest and most effective in veterinary medicine.