Cat bites and scratches can be fatal to pet birds. The Pasteurella multocida bacteria can go systemic reapidly and a bird who looks fine after a bite or scratch can be dead in the next couple days. That is why whenever a bird has had an altercation with a cat I always put them on antibiotics preventatively.
Here is an article about the danger of cat bites in people, from the AVMA Pet Health SmartBrief.
Cat bite puts woman in the hospital with a serious infection
“A cat bite is nothing to trivialize,” said Nancy Peterson, cat programs manager at the Humane Society of the United States.
Up to 50 percent of cat bites become infected, said Princy N. Kumar, head of the infectious-diseases division at MedStar Georgetown University Hospital. But, like me, many people don’t take the injury seriously enough.
“People underestimate” the danger, Kumar said, and don’t realize they should get a bite looked at right away. “They don’t realize, being bitten by a cat, you’ve got a 1-in-2 chance of getting infected.”
My first mistake was getting in the middle of a fight.
Sammy, a street cat who had just joined our family, did not like established resident Blue. When I heard a blood-curdling yowl from the spare bedroom late one night, I decided to remove one of the combatants.
When I reached down to pick him up him, Sammy wrapped his legs around my right arm and plunged his teeth into my wrist. Deep-red, venous blood ran out of two puncture wounds, and the area began to swell. I washed the wound well (after shrieking and dropping the cat), put some ice on it and kept it elevated for a while. I figured the swelling would be gone by morning.
The next day, my arm was puffy and I couldn’t move my fingers well. My wrist felt hot to the touch. I tried more ice and elevation.
That was my second mistake: minimizing the problem and treating the bite myself. A significant cat bite always requires medical intervention,
“If you got a really bad bite, you should get prophylactic antibiotics,” Kumar said. A light nip is not a problem, she said, but seek help if the cat has really sunk its teeth in — “if you see a puncture wound and blood coming out of it.”
Unlike dogs, which tend to deliver superficial, crushing bites that don’t penetrate far into tissue, cats inflict puncture wounds with their long teeth, which inject bacteria from the cat’s mouth and the environment deep into tissue.
And, Peterson said, “cats have a pretty potent bacteria.” While cats have a variety of microbes living in their mouths, the real trouble comes from Pasteurella multocida, a bacterium that can cause bad infections. One study found that 90 percent of domestic cats are carriers. Dogs also carry this bacteria, first isolated by Louis Pasteur and named after him, but the infection rate from their bites doesn’t come close to cats’ 50 percent. (Pasteurella is not the microbe that causes cat scratch disease, which is usually transmitted by kitten scratches and nips, and in most people causes only swollen lymph nodes, not severe local infection.).