Can fleas make a kitten sick?

A heavily infested animal, over time, can lose a substantial amount of blood to fleas. This is mostly the case in very young or frail animals. 70 fleas can consume 1 mL of blood per day which could kill a puppy or kitten in 50 days. Double the number of fleas and the young animal can be dead in a month. They lose so many red blood cells to the fleas that they become anemic and die.