This is what they done until now..

ask the vet if the med testing shows Hemobartonellosis or any of feline Hepatitis infections. I had a similar case back when I picked my first cat fresh off the street, and our vet treated him for this infection. I rang the alarm bell when I realized my cat's skin went from pale to yellow. They treated him for Hemobartonellosis. It took a week of therapy but it worked